Engineering reference

Follow the water levels. Inspect every loss.

Hydraulic basis, visible calculation chain, pipe-family matrices, source citations, and engineering limits for reviewing Water Siphon published numbers.

Use this reference to verify how screening-level flow, head, velocity, and equivalent pump-energy numbers are derived. It is a technical checking reference for engineers reviewing methodology, not a site-specific design submission.

Site-specific design still requires crest elevation and vacuum-margin review, pipe-class checks, tailwater review, transient analysis, equivalent pump benchmark review, and consenting review.

Controlled edition
2.2.0
Calculation regimes
Three, kept separate
Use boundary
Screening, not design
Registered 252 mm Water Siphon unit: hydraulic primer dome with gauge and bellows above the manifold body and inspection port, gear-driven butterfly isolation valve with handwheel on the outlet side, and HDPE stubs at both ends.
The 252 mm Water Siphon unitThe registered 252 mm unit — primer, manifold and isolation valve — the hardware the siphon method below refers to.

What the reference establishes

The reference separates the three hydraulic regimes, exposes the assumptions behind the published screening values, and identifies the checks that remain project-specific. The summary values below are navigation aids; the equations, worked example, matrices, evidence grades, and limits remain the controlling detail.

Pipe families
Concrete / PVC / PE

Gravity capacity and siphon capacity are separated by material and hydraulic regime.

Partial-flow states
10 / 25 / 50%

Fixed circular-pipe operating states used to interpret realistic gravity flow.

Reference water-level difference
1-8 m

Steady-state siphon range used in the PE SDR17 screening tables.

Worked example
200 mm / 200 m / 2 m

Single verification chain tying gravity, siphon, and pump benchmark outputs together.

Lab display units
m³/min · L/s · m/s

Operating rows show primary flow, secondary flow, velocity, tanks/day, and pump-cost benchmark context.

Scope and system definition

The Water Siphon system is an actively primed, pressurised closed-pipe siphon for groundwater management and stormwater drainage. The hydraulic primer maintains vacuum at the crest so the pipe can remain full and move water up and over obstacles within the practical crest-height envelope.

The distinction that matters for the calculations is operational versus hydraulic. Operationally, meaning priming, vacuum maintenance, and crest lift, the system stays ready to run. Once running, the pipe is treated as a standard full pressure-pipe problem driven by the head differential between the intake water surface and the discharge water surface.

Every Water Siphon flow number in this reference assumes that same actively primed product running as a full pressure pipe. The comparison is screening-level: it compares natural-fall gravity drainage, Water Siphon closed-pipe flow, and an equivalent pump-energy benchmark. It is not a detailed design, construction specification, pump schedule, or consenting assessment; site-specific design still requires the checks listed in the limits section.

Terms used in the tables

The matrices use pipe catalogue language and hydraulic shorthand. These definitions are included here so the tables do not assume prior familiarity.

OD
Outside diameterCatalogue PE pipe sizes are usually named by outside diameter. Hydraulic flow is calculated from internal diameter, not OD.
ID
Internal diameterThe diameter used in the flow equations. The catalogue tables use supplier mean IDs where available; DN and OD are not silently treated as ID.
SDR17
Standard dimension ratio 17PE pipe wall-thickness class where outside diameter divided by wall thickness is 17.
PE100
Pressure-pipe material classPolyethylene pressure-pipe grade used for the closed, fully primed siphon pressure-pipe tables.
DN
Nominal diameterCatalogue sizing language used for concrete and PVC gravity pipes. DN is a family label, not always the measured internal bore.
ΔH
Water-surface head differentialElevation difference between source and discharge water surfaces. It is not the crest height.
ΣK
Minor-loss allowanceA screening sum for fittings, valves, bends, intake, and outlet losses.
TDH
Total dynamic headPump benchmark head made up of static lift, pipe friction, and minor losses.

Source basis by method

Reference numbers map each method family to its governing source basis. Full citations are listed at the end.

Open-channel gravity

Manning full-bore reference, circular partial-flow geometry, and conservative concrete roughness basis.

Chow, Open-Channel Hydraulics, 1959; NZS 4404 roughness guidance; concrete-pipe design guidance.

Plastic gravity pipe

PVC SN4 Manning roughness basis and supplier internal-diameter interpretation where published.

NZS 4404 smooth-plastic roughness guidance plus Marley and Iplex PVC product resources.

PE siphon pressure pipe

Darcy-Weisbach pressure-pipe flow, Swamee-Jain turbulent screening basis, PE roughness, and supplier mean-ID pipe dimensions. Current published cases sit inside the turbulent screening envelope.

Swamee and Jain, 1976; Iplex Poliplex PE dimensions; PE100+ Association technical guidance.

Pump-energy benchmark

TDH, shaft-power, specific-energy, and daily electricity-cost convention used only as an equivalent benchmark.

Cameron Hydraulic Data, Karassik Pump Handbook, and WSAA pressure-pipeline guidance.

Rainfall volume screen

The rainfall volume method is a quick volume-and-drain-down screen. It is not a rainfall-runoff hydrograph, consent design, or site-specific drainage model.

Water Siphon internal screening convention, MBIE E1/VM1 Rational Method context, NRCS single-event hydrology tools, and FHWA HEC-22 drainage-design framing.

Worked example and matrix basis

Calculation chain for the stated defaults, worked example, and PE/concrete/PVC matrix extracts.

The worked example, equation sections, and pipe-family matrices in this Engineering Reference.

Field evidence

The field case is evidence from one site. It supports the operating story but is not treated as instrumented validation at scale.

Morelands Kaipara operator evidence and New Zealand pastoral drainage literature.

Method basis and three regimes

Source provenance frames three calculation regimes that remain separate: open-channel gravity, fully primed Water Siphon pressure flow, and the equivalent pump benchmark.

Three calculation families, kept separate

The reference separates the three methods before showing any matrix values. Gravity drainage is open-channel Manning flow, the Water Siphon is a closed pressure-pipe calculation, and the pump row is a matched-flow energy benchmark.

This separation is deliberate. It stops partial-flow drainage assumptions being mixed with closed-pipe siphon hydraulics, and it stops the pump comparison from being read as a pump schedule.

Gravity drainage

Manning + circular partial-flow geometry

Used for concrete and PVC drainage interpretation. The full-bore row is a reference boundary; the 25% row is the headline part-full state.

Water Siphon running flow

Darcy-Weisbach + Swamee-Jain

Used only once the line is primed and acting as a full pressure pipe. Default and published matrix cases sit inside the turbulent screening envelope.

Equivalent pump benchmark

Matched flow through the same line

Used for shaft-power, specific-energy, and NZ$/day context. It includes static lift, pipe friction, and minor losses, but remains a benchmark rather than a pump design.

Gravity drainageAir spaceWater SiphonPump benchmarkSumpGravity drainageAir spaceWater SiphonPump benchmarkSump
  • Part-full gravity — Manning and circular geometry.
  • Full-pressure pipe — Darcy-Weisbach and Swamee-Jain.
  • Pump benchmark — total dynamic head and shaft power.
Three hydraulic calculation regimesGravity, Water Siphon, and pump outputs remain separate because each answers a different engineering question.

Water-level difference and crest height answer different questions

The Water Siphon can route water up and over a crest because the primer establishes and maintains the closed-pipe condition. Once the line is running, the hydraulic solver does not treat the physical high point as the available driving head.

The difference between the source and discharge water surfaces provides the driving energy for flow; the formulas call this ΔH. Crest lift is a separate feasibility constraint checked for vacuum margin, pipe profile, and practical installation limits.

In the worked reference case, the flow solver uses 2.00 m siphon ΔH, not the crest height. That distinction is why the comparison can describe water moving over an obstacle while still using a conventional pressure-pipe head-loss equation.

Crest liftΔH
  • Driving head ΔH — the water-level difference that drives flow.
  • Crest lift — a separate vacuum-margin and route-profile check.
Driving head and crest lift are separate checksThe water-level difference is the running-flow energy term; crest elevation remains a separate vacuum-margin and route-profile constraint.

Flow driver

2.00 m siphon ΔHThe worked example solves the pressure-pipe flow from the water-surface differential.

Separate feasibility check

Crest liftCrest lift controls vacuum margin and installation feasibility; it is not substituted for ΔH in the running-flow equation.
Route fitting-loss decomposition (calculator estimate)

The calculator can decompose ΣK from the canonical siphon geometry — intake drop, up-line, crest, down-line, exhaust drop — using large-bore flanged loss coefficients. The estimate totals K ≈ 3.92, inside the typical 2–4 installation band. The registered screening default remains ΣK = 2.0; applying the estimate is an adjusted assumption. The Manifold body and its internal non-return valve are not separately modelled pending an engineering figure, and joint effects (rubber-ring sockets, butt-fusion beads) are covered by the clean-pipe roughness basis rather than a per-joint coefficient: no universal per-joint constant is supportable, since bead losses depend on bead geometry and workmanship. The ΣK control spans 0–6 to admit the estimate; the registered sensitivity envelope (0–4) is unchanged.

ReferenceCountK eachSubtotal
Submerged intake entrance (square-edged)10.500.50
Intake riser bends, 90° long-radius20.280.56
Up-line grade bends, ≤45° sweep20.200.40
Down-line grade bends, ≤45° sweep20.200.40
Exhaust riser bends, 90° long-radius20.280.56
Gear-driven butterfly isolation valves, fully open20.250.50
Submerged outlet exit11.001.00
Estimated ΣK (baseline geometry)——3.92

Partial-flow gravity is the realistic operating comparison

Gravity drains do not normally operate as pressurised full pipes. The full-bore Manning row is kept because it is a useful full-bore reference, but the headline comparison uses part-full circular-pipe states.

The partial-flow constants are deterministic: at 10% Q/Q_full, y/D = 0.214; at the 25% headline operating state, y/D = 0.341; and at 50%, y/D = 0.500. Those values are geometry outputs, not presentation estimates.

The 25% headline operating state is used because it gives engineers a conservative part-full gravity condition while keeping the full-bore boundary visible for reference. Q/Q_full peaks near y/D = 0.938, which is why “deeper” does not scale linearly with discharge through the whole range.

Manning partial flow, circular gravity pipeGravity comparison onlyθA(y)air spaceP(y) wetted perimeterDycrowninvert0.000.250.500.751.000.000.250.500.751.00Q / Q_fully / Dpeak 1.08 at y/D 0.93810 % at y/D 0.21425 % at y/D 0.341screening reference state50 % at y/D 0.500100 % at y/D 1.000y/D from invert · θ 143° at referencen, S constant · siphon never part-fullManning partial flow · gravity onlyθA(y)air spaceDyP(y) wetted perimeter · θ 143°0.000.250.500.751.000.000.250.500.751.00Q / Q_fully / Dpeak 1.08 at 0.93810 %25 % reference50 %100 %y/D from invert · n, S constant
Gravity regime — Manning partial-flow sequenceGravity comparison only. The section and ratio plot describe Manning open-channel partial flow in a circular gravity pipe—not the pressurised, fully primed Water Siphon line. The calculated operating ratios and constants remain below for technical reference.

10% state

0.214 y/DVery shallow operating point used to show the low-flow end of the circular-pipe relationship.

25% headline operating state

0.341 y/DThe headline gravity comparison row uses this part-full state rather than claiming normal full-bore operation.

50% state

0.500 y/DAt half depth, velocity equals the full-bore Manning reference in this deterministic geometry set.

Pump TDH is the full line-loss benchmark, not static lift alone

The pump row answers a narrow question: what shaft power would be required to move the matched siphon flow through the same pipe route using an electric pump benchmark?

Pump TDH distinguishes 2.00 m siphon ΔH from 4.00 m pump TDH in the worked case. The pump benchmark includes the 2.00 m static component plus 1.77 m friction and 0.23 m minor losses through the same 200 m line.

The public calculator also converts shaft power into kWh/day and NZ$/day using an editable electricity-price assumption. The current default is NZ$0.30/kWh. Changing that price changes the cost benchmark only; it does not change hydraulic flow, velocity, TDH, or shaft power.

This is why the page describes the pump result as “matched transfer · energy benchmark only.” It gives engineering context for energy and power, but it does not specify a pump, motor, duty cycle, control system, or NPSH margin.

Siphon calculation

2.00 m siphon ΔHClosed-pipe flow is solved from the available water-surface differential.

Pump TDH

4.00 m pump TDHStatic lift plus full-line losses through the same pipe route.

Loss split

1.77 m friction · 0.23 m minorRounded components from the worked benchmark chain.

Cost display

NZ$/day = kW × 24 × priceDisplayed cost uses the editable electricity price, defaulting to NZ$0.30/kWh.

Governing equations

The reference is built on three equation families: Manning for gravity, Darcy-Weisbach with Swamee-Jain for the siphon, and matched-flow pump power for benchmarking. It retains pressure-pipe friction and minor losses rather than using a lossless Bernoulli shortcut.

Manning full-bore and partial-flow

Gravity capacity is tabulated from the full-bore Manning reference and then interpreted through realistic circular partial-flow states. The full-bore row is a reference boundary, not a claim that a gravity drain normally runs pressurised.

Q_full=(1 / n) × A × R^(2/3) × S^(1/2)θ=2 × arccos(1 − 2 × y/D)A(y)=D² / 8 × (θ − sin θ)P(y)=D × θ / 2Q(y/D)=(1 / n) × A(y) × R(y)^(2/3) × S^(1/2)

Darcy-Weisbach siphon flow

The siphon is treated as a closed, fully primed pressure pipe. Total head differential drives flow; crest lift is a separate vacuum-margin and installation check, not the flow driver itself. The current solver preserves the Swamee-Jain screening output and reports whether custom inputs remain inside the turbulent screening envelope.

ΔH=(f × L / D + ΣK) × v² / (2g)f=0.25 / (log10(k_s / (3.7 × D) + 5.74 / Re^0.9))²Re=v × D / νQ=A × v

Equivalent pump benchmark

The pump comparison is a matched-flow shaft-power benchmark only. The public NZ$/day value is a cost conversion from shaft power and an editable tariff assumption; it gives energy context without becoming a pump schedule, duty validation, or NPSH review.

TDH=H_static + H_friction + H_minorP_shaft=ρ × g × Q × TDH / ηE_kWh_per_ML=ρ × g × TDH × 1000 / (η × 3.6 × 10⁶)C_day=P_shaft,kW × 24 × price_NZ$/kWh

Site atmospheric conditions

Optional site inputs — altitude (0–3000 m) and water temperature (0–30 °C) — set the atmospheric and viscosity basis behind the crest screen. Each part of that basis, and its limit, is stated below.

Pressure and vapour
Atmospheric pressure from the NASA troposphere fit; saturation vapour pressure from the NIST Antoine parameter set, evaluated within its 273–303 K validity (the band’s 30 °C top is held at the 303 K endpoint).
Viscosity
Kinematic viscosity from a Vogel-form correlation validated by unit test against the IAPWS 25 °C reference point (within 0.1%) and the solver’s 10 °C basis; its deviation grows to roughly 2% at 0 °C, which remains screening-adequate because viscosity enters only through the friction factor’s weak Reynolds dependence.
Crest implication
The barometric head is the practical crest ceiling for ordinary gas-containing water. The full operating limit also carries a velocity-head term v²/(2g); that term is deliberately excluded from the site shift and is covered, with the other installation margins, by the published crest screening ladder’s owner calibration. The ladder shifts down by the site’s barometric-head deficit against the sea-level, 10 °C reference basis and never loosens above the published reference.
Density
Held at 1000 kg/m³ (variation under 0.5% across the band).
T_air=15.04 − 0.00649 × hp_atm=101.29 × ((T_air + 273.1) / 288.08)^5.256  [kPa]p_v=100 × 10^(5.40221 − 1838.675 / (T_K − 31.737))  [kPa, from the Antoine bar form]μ=2.414 × 10⁻⁵ × 10^(247.8 / (T_K − 140))ν=μ / ρH_baro=(p_atm − p_v) × 1000 / (ρ × g)  [m of water, both pressures in kPa]

Map-derived site inputs

The calculator’s optional site locator derives three inputs from the drawn route and the LINZ NZ 8 m DEM. Every derived value lands in an ordinary editable input for correction against site knowledge.

Route length
From the drawn route polyline (great-circle geometry).
Altitude
The DEM ground elevation at the intake end, clamped to the calculator’s 0–3000 m altitude input range, so a below-datum DEM value applies as 0 m.
Crest estimate
The highest sampled DEM ground elevation above the UNCLAMPED intake ground along the drawn line (at most 33 samples; spacing stays under 45 m at the drawing limits).
Data precision
The DEM is interpolated from 20 m topographic-map contours, so every derived value is a coarse ground-profile screening estimate — never a water-surface or pipe level.
Water-level exclusion
The water-level difference is never derived from the map: ground elevation is not water level, and the driving head must come from the two measured water surfaces.
Water temperature
Where the locator assumes a water temperature it applies the NIWA climate-normals basis for the nearest published location from the regional table in this reference.
L_route=Σ great-circle segment lengths along the drawn linez_site=clamp(DEM ground at intake, 0–3000 m)crest_est=max(0, max(DEM samples) − z_intake)

Defaults and assumptions

These are the screening values used throughout the reference. Each value is paired with its interpretation and provenance so changes can be reviewed before any numerical output is revised.

Reference itemValueInterpretationSource basis
Concrete Manning n0.012Clean machine-made concrete reference used as a conservative gravity baseline.NZS 4404 roughness guidance and Chow open-channel reference.
PVC / PE smooth-plastic Manning n0.009Smooth-bore gravity reference for PVC SN4 and PE pipe in gravity/open-channel mode.NZS 4404 smooth-plastic range plus Marley, Iplex PVC, and Iplex PE product resources.
Plastic pressure-pipe roughness k_s0.003 mmClean new plastic pressure-pipe roughness used in the Darcy-Weisbach solver for PVC/PE pressure comparisons.Iplex PE hydraulic design guidance and PE100+ technical guidance.
Pressure-pipe friction regimeSwamee-Jain turbulent screeningDefault and published matrix cases are inside the screening envelope. Current PE matrix rows stay above Re 48,000, and the verifier checks Swamee-Jain against an implicit Colebrook-White solve with worst flow delta below 0.4%.EPANET 2.2 Darcy-Weisbach regime framing, Colebrook-White verifier sweep, and Water Siphon production guardrail metadata.
Minor-loss sum ΣK2.0Screening allowance for intake, bends, valves, and outlet losses. It is not a validated Water Siphon system constant. The calculator can decompose a route estimate from the canonical siphon geometry (see the fitting-loss table); its control spans 0–6 while this registered default and the 0–4 sensitivity envelope are unchanged.Standard pumping-hydraulics convention; sensitivity range held for design review.
Pump efficiency η0.70Benchmark shaft efficiency only; motor, drive, transformer, and tariff effects are outside scope.Preliminary pump-benchmark convention from standard pump references.
Electricity priceNZ$0.30/kWhEditable public calculator assumption used to convert pump benchmark shaft power into NZ$/day.Water Siphon screening convention.
Tank equivalent volume25,000 LDisplay-only benchmark for tanks/day and storm-volume equivalents. It does not change hydraulic capacity.Water Siphon screening convention.
Reference run length200 mStandard PE siphon comparison length used for the matrix and worked example.Screening convention reproduced in the worked example and pipe-family matrices in this reference.
Screening sequenceMethod review onlyDeclared inputspipe family, borelength, route, ΔHtailwater stateRegime splitpart-full gravityprimed pressure pipepump benchmarkEquation chainflow, velocity, headfriction, minor lossesenergy contextReview gatevacuum, pipe classtailwater, transientsproject checksHand-off boundarysupports method review onlydoes not become construction · procurement · consenting · site-specific designScreening sequence · method review onlyDeclared inputspipe family, borelength, route, ΔHtailwater stateRegime splitpart-full gravityprimed pressure pipepump benchmarkEquation chainflow, velocity, headfriction, minor lossesenergy contextReview gatevacuum, pipe classtailwater, transientsproject checksHand-off boundarydoes not become construction,procurement, consenting or site design
  • 1 Declare — geometry and conditions.
  • 2 Separate — choose the hydraulic regime.
  • 3 Calculate — show the equation and defaults.
  • 4 Review — keep project-specific limits visible.
From stated inputs to a bounded screening resultThe reference exposes inputs and methods, then stops at the boundary where project-specific design checks begin.

Screening extensions

Tailwater, storm stage, and rainfall volume extend the base comparison without turning the screening model into a site hydrology or backwater design model.

Tailwater and storm‑stage screening

This reference treats receiving-water rise and storm-stage rise as one signed stage problem. The normal upstream water surface is datum 0. Storm flooding raises that source stage, while the downstream outlet starts at the normal gross drop and rises with tide, storm surge, or receiving-drain backup.

The signed net head is used for interpretation. Positive net head gives forward discharge, zero net head is a primed standing condition, and negative net head is a reverse-head condition requiring isolation or backflow-control review before relying on discharge.

Gravity flow keeps the free-outlet reference visible, but the operating screen uses the clamped hydraulic-grade slope from the current net head. The pump row estimates the shaft power needed to maintain the normal-stage target transfer during the current stage condition; it is not a pump curve or selection.

The cited manuals support the boundary-condition, tailwater, and dynamic-routing context. The exact steady-stage equations in this section are Water Siphon NZ screening abstractions, not FHWA, SWMM, or HEC-RAS design equations.

+ H_netH_net = 0− H_net
  • Positive head — forward discharge.
  • Zero head — primed and standing.
  • Negative head — isolation review.
Positive, zero, and negative tailwater statesSigned net head distinguishes forward discharge, a standing primed condition, and reverse-head conditions requiring isolation or backflow review.

Stage equation

H_net = H_gross + H_upstream_storm - H_tailwaterSigned head from the current source stage to the current downstream receiving stage; an internal steady-stage screening convention.

Gravity screen

S_screen = max(H_net / L, 0)Internal screening hydraulic-grade slope only; outlet-control and drowned-outlet cases still need backwater analysis.

Pump stage screen

Pump TDH_current = max(H_friction,target + H_minor,target - H_net, 0)Internal energy-benchmark screen. Target losses are computed at the normal-stage transfer; positive natural head is credited before pump TDH is reported.
Reference default stage-impact matrix

DN225 PVC SN4 pipe (237.9 mm internal diameter), 200 m route, 2.0 m gross drop, 25% gravity basis. Pump power maintains the normal-stage Water Siphon target transfer of about 74 L/s.

ReferenceNormalTide +1.0 mTide +2.0 mStorm +1.0 m with tide +2.0 mTide +2.5 m reverse-head
Net head / state2.0 m forward1.0 m forward0.0 m stalled1.0 m forward-0.5 m reverse
Gravity screened flow / status19 L/s free-outlet reference13 L/s stage-screened; backwater check0 L/s stalled; outlet-controlled13 L/s stage-screened; backwater check0 L/s reverse-head; isolate/check
Water Siphon flow / status74 L/s running51 L/s running0 L/s primed/standing51 L/s running0 L/s reverse-head/isolation check
Pump TDH / kW to hold target transfer0.0 m / 0.00 kW1.0 m / 1.04 kW2.0 m / 2.07 kW1.0 m / 1.04 kW2.5 m / 2.59 kW

Rainfall drain-down is a volume screen, not a hydrologic design model

The rainfall volume method answers one deliberately narrow farmer question: if this much rain falls over this much area, and this many millimetres are absorbed or held before becoming connected water, how long would the selected method take to move the remaining storm volume at the current steady flow?

The input labelled “Absorbed / held by ground” is a screening depth. It represents rainfall held in soil storage, surface depressions, pasture or interception, and the lowered pre-storm groundwater profile. It is not a measured infiltration rate, runoff coefficient, or groundwater drawdown model.

This screening method assumes the Water Siphon system has already been installed and operating before the event, so groundwater starts within the intended lowered operating range. The calculation does not simulate groundwater drawdown during the storm; it divides the selected connected storm volume by the current screened pipe-flow rate.

The rainfall input is an event-total depth. It does not model rainfall intensity or storm duration. A 60 mm event over 2 hours and a 60 mm event over 24 hours produce the same gross rainfall volume, but not the same field flooding response. Duration, intensity, infiltration, inlet loading, catchment routing, and downstream stage over time are outside this screening method.

Water to move depth

water_to_move_mm = max(rainfall_mm - absorbed_mm, 0)Converts the stated rainfall and absorbed-depth assumptions into the connected storm depth.

Gross rainfall volume

V_gross = rainfall_mm / 1000 × A_ha × 10,000Converts rainfall depth over hectares into cubic metres of rain falling on the catchment.

Absorbed / held volume

V_absorbed = absorbed_mm / 1000 × A_ha × 10,000Converts the absorbed-depth assumption into an equivalent volume for transparency.

Storm volume to move

V_move = water_to_move_mm / 1000 × A_ha × 10,000This is the connected storm volume divided by the selected method flow.

Theoretical pipe time

t_pipe_h = V_move / Q_m³/hUses the selected method steady flow, or pump benchmark target flow, and is independent of active flow hours.

Calendar window

t_calendar_days = V_move / (Q_m³/h × h_active × duty_factor)Active flow hours and duty factor affect daily/calendar summaries only; they do not change instantaneous hydraulic capacity.
Reference rainfall screening default

Reference screening scenario: 0 mm over 10 ha, with 0 mm absorbed or held by the ground and 0 mm remaining as connected storm depth. The calculation uses the selected flow and does not hard-code a final time in this reference.

ReferenceValueCalculation note
Rainfall total0 mmReference input
Absorbed / held by ground0 mmScreening assumption; not a measured infiltration rate
Water to move0 mmmax(0 mm - 0 mm, 0)
Gross rainfall volume0 m³0.000 m × 10 ha × 10,000
Absorbed / held volume0 m³0.000 m × 10 ha × 10,000
Storm volume to move0 m³0.000 m × 10 ha × 10,000
Time calculationV_move / selected flowSelected method flow or pump benchmark target flow in m³/hour
Outlet-condition screening assumptions

Outlet condition separates instantaneous stage/head assumptions from daily operating-window summaries.

ReferenceActive flow assumptionStage interpretationLimitation
Non-tidal / free outlet24 h/dayOutlet remains below source stageScreening only.
Tidal outlet10 h/dayFlow shown during assumed favourable low-water stageNot a tide-table substitute.
Backed-up outlet0 h/dayTailwater set to current source stage; no forward headSite levels required.
Custom / engineer settingUser-setUser controls stage and window assumptionsProfessional judgement required.
Regional screening water-temperature basis (NIWA 1991–2020 normals)

The assumed screening water temperature is the mean annual 10 cm earth temperature where NIWA publishes one — the closest official proxy for shallow groundwater and drain water — falling back to the mean annual air temperature. The calculator applies a value only through the site-location flow; the temperature input remains manual and adjustable, and the published matrices keep their 10 °C reference basis.

ReferenceMean annual air (°C)Mean annual 10 cm earth (°C)Assumed water (°C)
Kaitaia15.615.315.3
Whangārei16.0—16.0
Auckland15.615.315.3
Tauranga15.1—15.1
Hamilton13.913.613.6
Rotorua12.8—12.8
Gisborne15.115.415.4
Taupō11.9—11.9
New Plymouth13.8—13.8
Napier14.713.813.8
Whanganui14.113.713.7
Palmerston North13.413.013.0
Masterton13.213.013.0
Wellington13.112.412.4
Nelson13.112.412.4
Blenheim13.212.312.3
Westport12.8—12.8
Hokitika11.911.711.7
Christchurch11.610.910.9
Timaru10.810.810.8
Queenstown9.8—9.8
Alexandra10.3—10.3
Dunedin11.210.810.8
Invercargill10.19.49.4

Worked example — 200 mm reference case

Reference inputs: 200 mm internal diameter, 200 m pipe run, 2.00 m total head differential, PE k_s = 0.003 mm, ν = 1.3e-6 m²/s, ΣK = 2.0, and pump benchmark η = 0.70. Self-priming describes the Water Siphon operating mechanism; it is not a separate calculation version. The worked Water Siphon value is the 47.39 L/s result for this reference case.

  1. Input set

    200 mm / 200 m / 2.00 m ΔH

    The same reference inputs are carried through gravity reference flow, partial-flow interpretation, Water Siphon pressure-pipe flow, and equivalent pump-energy benchmarking.

  2. Gravity full-bore reference

    35.53 L/s

    At S = 0.010 and n = 0.012, A = 0.03142 m² and R = 0.050 m. Manning gives v_full = 1.131 m/s and Q_full = 35.53 L/s.

  3. Gravity at 25% partial-flow state

    8.88 L/s

    The deterministic α = 0.25 circular-pipe state resolves to y/D = 0.341 and v/v_full = 0.831. Discharge is 25% of the full-bore reference: 8.88 L/s.

  4. Water Siphon pressure-pipe flow

    47.39 L/s

    With PE k_s = 0.003 mm, ν = 1.3e-6 m²/s, L = 200 m, D = 0.200 m, ΔH = 2 m, and ΣK = 2.0, Swamee-Jain friction converges at f = 0.01524, v = 1.509 m/s, and Re = 2.32e5, inside the screening envelope.

  5. Equivalent pump benchmark

    2.66 kW / 15.57 kWh·ML⁻¹

    Matching the siphon duty through the same main gives H_friction = 1.767 m, H_minor = 0.232 m, TDH = 4.00 m, 2.66 kW shaft power, and 15.57 kWh per megalitre at η = 0.70.

Sensitivity

This table is a calculation audit for the OD225 / 3 m PE matrix scenario. It is not a second Water Siphon product version. The key lesson is that actual internal diameter affects siphon flow far more than smooth-plastic roughness within the defensible research band.

Internal diameter and roughness audit

OD225 PE100 SDR17 scenario, 200 m line, 3 m head differential, base k_s = 0.003 mm, ΣK = 2.

ReferenceFlow (L/s)Interpretation
Base case, k_s = 0.003 mm, ID 197.8, ΣK = 257.4Reference OD225 / 3 m scenario using the supplier mean ID.
Lower smooth-plastic roughness, k_s = 0.0015 mm57.6Very small change from the base scenario.
Upper research roughness, k_s = 0.007 mm57.0Very small change from the base scenario.
Upper NZ service roughness, k_s = 0.015 mm56.3Still a modest roughness effect.
Nominal OD used incorrectly as ID, 225 mm79.9Large error because OD is not the hydraulic diameter.
No minor-loss allowance, ΣK = 061.5Shows why fitting losses are retained in screening.

Validation and reproducibility

The numbers are reproducible from the equation chain, defaults, and tabulated values in this reference. The reference methods use the same equation families and defaults for input-specific checks.

  • Manning gravity, circular partial-flow ratios, Darcy-Weisbach siphon flow, and equivalent pump energy are kept as separate equation families.
  • The worked example and pipe-family matrices are verified against the hydraulic routines used by the screening calculations.
  • The hydraulic verifier prints a deterministic length sweep with length, head, flow, velocity, Reynolds screening status, friction basis, daily volume, and storm pipe-hours.
  • The public operating rows display m³/min as the primary flow unit, with L/s and m/s retained as engineering secondary values. Tank equivalents and NZ$/day are display conversions only.
  • The hydraulic verifier checks the public PE matrix against an implicit Colebrook-White turbulent reference; current rows stay above Re 48,000 with worst flow delta below 0.4%.
  • The reference methods share the same equation basis, so custom inputs and reference defaults stay comparable.
  • Any project that changes pipe class, roughness, route length, fittings, head differential, or pump efficiency requires recalculation before the numbers are used for design decisions.
Reynolds regime gateLog axis, decade ticksLaminarRe < 2,300Published matrix floorRe 48,000Worked exampleRe 2.32e5Turbulent flowRe > 4,0001e31e41e51e6TransitionRe 2,300 – 4,000Swamee–Jain minimumRe 5,000Published matrix coverageReynolds regime gate · log axisMatrix floor Re 48,000Worked Re 2.32e55,000Turbulent, Re > 4,0001e31e41e51e6Laminar Re < 2,300transition Re 2,300–4,000matrix coveragefrom the matrix floorSwamee–Jain minimum Re 5,000
  • Laminar region — Reynolds number below 2,300.
  • Transition region — Reynolds number from 2,300 to 4,000.
  • Turbulent flow — Reynolds number above 4,000.
  • Swamee–Jain correlation — Reynolds range 5,000 to 100,000,000, with separate relative-roughness limits; the axis shows only part of this range.
  • Published matrix coverage — cases begin above Reynolds number 48,000. Public results must also pass the separate screening validity envelope.
Reynolds regime gatePublished matrix cases begin above Re 48,000. The Swamee–Jain correlation has a separate Reynolds range of 5,000 to 100,000,000 and relative-roughness limits. Public results must also pass the separate screening validity envelope; turbulence alone does not establish site suitability.

How to read the matrices

  • Treat full-bore gravity capacity as a reference condition. Real gravity drainage should be checked at realistic part-full operating states and freeboard conditions.
  • Use concrete tables only for gravity interpretation. PVC SN4 and PE SDR17 rows separate catalogue size from hydraulic bore; Water Siphon and pump benchmarks use valid smooth-plastic pressure-pipe selections, with project-specific pipe class and vacuum suitability still requiring engineering review.
  • Read ΔH as the total head differential between upstream and downstream water surfaces; do not substitute crest lift for ΔH in the siphon calculation.
  • Use the pump benchmark for energy and power context only. It is not a pump schedule, duty validation, procurement recommendation, or NPSH review.
  • Use these matrices only within the stated assumptions. Project-specific pipe class, roughness, route length, fittings, and head conditions require project-specific recalculation.

Pipe family matrices

These tables expose the pipe families, operating states, and benchmark values used by the screening numbers. Each caption states the equation family, defaults, and pipe-property basis so a reviewer can spot-check cells independently. DN and OD entries are catalogue labels; hydraulic calculations use the internal diameter shown beside the row where supplier IDs are available.

Matrix 1 - current New Zealand size availability

6 rows · 3 columns

Catalogue families used by the calculator. PVC and PE rows use supplier mean internal diameters where published; concrete remains a gravity/open-channel nominal-DN reference.

ReferenceSupplier referenceCatalogue size rangeUse in this reference
PVC SN4 stormwater pipeMarley Stormline / Iplex NovadrainDN90-DN375Default farmer-facing band to DN300; DN375 gravity-only reference.
Concrete roller compacted pipeHumes RCPDN225-DN600Small and medium gravity stormwater, culvert, and drainage.
Concrete radial press pipeHumes TITAN RPDN675-DN1050Large-diameter stormwater and culvert range.
Large-diameter concrete pipeHynds PinnacleDN675-DN3000Large-diameter concrete option in NZ market.
PE100 SDR17 / PN10 pressure pipeIplex PoliplexOD110-OD1800 in the selectorPressure-pipe family suitable as leakproof siphon pipe basis; OD-labelled, supplier-ID calculated.
PE pressure / drainage pipe range cross-checkHynds PEDN16-DN2000Broad NZ PE range cross-check; fake PE375 and PE1500 selector rows are not used.

Partial-flow operating constants

3 rows · 3 columns

Deterministic circular-pipe ratios used across the gravity interpretation work.

Referenceα = Q/Q_fully/Dv/v_full
10% operating state0.100.2140.639
25% operating state0.250.3410.831
50% operating state0.500.5001.000

Concrete gravity full-bore capacity (L/s)

10 rows · 5 columns

Full-bore Manning reference at n = 0.012. This is a full-bore reference, not a prescribed operating depth.

Reference0.50%0.75%1.00%1.50%2.00%
DN22534.442.148.659.668.8
DN30074.190.7104.8128.3148.2
DN375134.3164.5189.9232.6268.6
DN450218.4267.5308.9378.3436.8
DN525329.4403.5465.9570.6658.9
DN600470.4576.1665.2814.7940.7
DN675643.9788.6910.611151288
DN750852.81044120614771706
DN90013871698196124022774
DN105020922562295836234184

Concrete gravity 25% operating state (L/s)

10 rows · 5 columns

Inverse-solved circular partial-flow state at y/D = 0.341 and v/v_full = 0.831.

Reference0.50%0.75%1.00%1.50%2.00%
DN2258.610.512.214.917.2
DN30018.522.726.232.137.0
DN37533.641.147.558.267.2
DN45054.666.977.294.6109.2
DN52582.4100.9116.5142.7164.7
DN600117.6144.0166.3203.7235.2
DN675161.0197.2227.7278.8322.0
DN750213.2261.1301.5369.3426.4
DN900346.7424.6490.3600.5693.4
DN1050523.0640.5739.6905.81046

PVC SN4 gravity full-bore capacity (L/s)

7 rows · 5 columns

Full-bore Manning reference at n = 0.009 for smooth plastic gravity pipe. Rows use supplier mean ID where published.

Reference0.50%0.75%1.00%1.50%2.00%
DN90 (ID 90.0)4.04.95.66.98.0
DN100 (ID 100.0)5.36.57.59.110.6
DN150 (ID 152.1)16.119.822.828.032.3
DN175 (ID 190.4)29.436.041.650.958.8
DN225 (ID 237.9)53.265.275.392.2106.4
DN300 (ID 299.7)98.5120.6139.3170.6197.0
DN375 (ID 380.7)186.4228.3263.7322.9372.9

PVC SN4 gravity 25% operating state (L/s)

7 rows · 5 columns

Inverse-solved circular partial-flow state at y/D = 0.341 and v/v_full = 0.831. Rows use supplier mean ID where published.

Reference0.50%0.75%1.00%1.50%2.00%
DN90 (ID 90.0)1.01.21.41.72.0
DN100 (ID 100.0)1.31.61.92.32.6
DN150 (ID 152.1)4.04.95.77.08.1
DN175 (ID 190.4)7.39.010.412.714.7
DN225 (ID 237.9)13.316.318.823.026.6
DN300 (ID 299.7)24.630.234.842.749.3
DN375 (ID 380.7)46.657.165.980.793.2

Matrix 3 - running siphon, PE SDR17 siphon discharge over 200 m (L/s)

24 rows · 8 columns

Darcy-Weisbach with Swamee-Jain friction factor, plastic k_s = 0.003 mm, and ΣK = 2. Rows use Iplex Poliplex SDR17 / PN10 mean IDs; no PE375 or PE1500 row is inserted. Coverage: every row here carries the corrected New Zealand drainage matrix, which restates the commissioned reference cases on corrected internal diameters and extends the same calculation chain from OD710 up to OD1800. Across the whole table the implied pipe velocity spans 0.66 to 7.15 m/s, so the faster rows are screening capacity at a velocity well above ordinary operating practice, not a recommended operating point.

Reference1 m2 m3 m4 m5 m6 m7 m8 m
OD110 (ID 96.5)4.87.18.810.411.713.014.115.2
OD125 (ID 109.9)6.810.012.514.616.518.219.821.4
OD140 (ID 123.1)9.113.416.819.622.224.526.728.7
OD160 (ID 140.7)13.019.023.827.831.434.737.840.6
OD180 (ID 158.3)17.725.932.337.842.747.151.255.1
OD200 (ID 175.8)23.234.042.449.655.961.867.172.2
OD225 (ID 197.8)31.646.157.467.175.783.690.897.6
OD250 (ID 220.0)41.560.575.488.199.4109.7119.1128.0
OD280 (ID 246.3)55.580.8100.6117.5132.4146.1158.7170.4
OD315 (ID 277.1)74.9109.0135.6158.3178.4196.7213.6229.4
OD355 (ID 311.1)100.5146.0181.5211.7238.5262.9285.4306.5
OD400 (ID 351.9)137.1198.8247.0287.9324.3357.3387.8416.3
OD450 (ID 395.9)184.0266.5330.8385.5434.0478.0518.7556.7
OD500 (ID 440.0)239.1345.9429.1499.8562.4619.3671.8720.9
OD560 (ID 492.7)315.8456.4565.7658.6740.8815.5884.5948.8
OD630 (ID 554.4)421.2607.9752.9876.0985.1108411751261
OD710 (ID 624.6)562.0809.9100211661310144115631675
OD800 (ID 703.9)748.21077133215481739191320732222
OD900 (ID 791.7)988.91421175720412292252027302926
OD1000 (ID 879.7)12671819224626092929322034873737
OD1200 (ID 1062.3)19622812346940264518496453755758
OD1400 (ID 1231.8)27543940485756336319694175138047
OD1600 (ID 1407.2)3721531865517594851693511012010837
OD1800 (ID 1585.6)486069398544990011099121841318314115

Equivalent pump shaft power to match siphon flow (kW)

6 rows · 3 columns

Shaft power to move the matched siphon flow through the same 200 m PE main at the stated static lift, including friction and minor losses. Not a pump selection.

Reference3 m lift5 m lift8 m lift
OD225 at 57.4 L/s4.836.448.85
OD315 at 135.6 L/s11.4015.2020.90
OD355 at 181.5 L/s15.2620.3527.98
OD450 at 330.8 L/s27.8237.0951.00
OD1000 at 2246 L/s189252346
OD1800 at 8544 L/s7189581317

Equivalent pump specific energy (kWh/ML)

1 rows · 8 columns

Head-only energy values at η = 0.70, excluding tariff and detailed pump-selection effects.

Reference1 m2 m3 m4 m5 m6 m7 m8 m
kWh/ML3.897.7911.6815.5719.4623.3627.2531.14

Minimum concrete DN for target flow

11 rows · 5 columns

Full-bore reference sizing matrix at Manning n = 0.012.

Reference0.50%0.75%1.00%1.50%2.00%
25 L/sDN225DN225DN225DN225DN225
50 L/sDN300DN300DN300DN225DN225
75 L/sDN375DN300DN300DN300DN300
100 L/sDN375DN375DN300DN300DN300
150 L/sDN450DN375DN375DN375DN375
200 L/sDN450DN450DN450DN375DN375
300 L/sDN525DN525DN450DN450DN450
400 L/sDN600DN525DN525DN525DN450
500 L/sDN675DN600DN600DN525DN525
700 L/sDN750DN675DN675DN600DN600
900 L/sDN900DN750DN675DN675DN600

Minimum PE SDR17 OD for target flow

11 rows · 8 columns

Minimum catalogue OD by siphon head differential over the 200 m reference run.

Reference1 m2 m3 m4 m5 m6 m7 m8 m
25 L/sOD225OD180OD180OD160OD160OD160OD140OD140
50 L/sOD280OD250OD225OD225OD200OD200OD180OD180
75 L/sOD355OD280OD250OD250OD225OD225OD225OD225
100 L/sOD355OD315OD280OD280OD280OD250OD250OD250
150 L/sOD450OD400OD355OD315OD315OD315OD280OD280
200 L/sOD500OD450OD400OD355OD355OD355OD315OD315
300 L/sOD560OD500OD450OD450OD400OD400OD400OD355
400 L/sOD630OD560OD500OD500OD450OD450OD450OD400
500 L/sOD710OD630OD560OD560OD500OD500OD450OD450
700 L/sOD800OD710OD630OD630OD560OD560OD560OD500
900 L/sOD900OD800OD710OD710OD630OD630OD630OD560

Field evidence — Morelands Kaipara

Morelands is a dairy operation on Kaipara marine clay. The owner/operator case is useful because it reports both water-level response and farm-production outcomes, but it remains one site, one operator, and one installation year.

These figures must not be generalised or used to predict outcomes for another site. They support only the bounded claim that lowering the resting groundwater table can materially change land performance where materially similar constraints are independently established.

Morelands reported outcomes

Evidence-grade language is intentionally explicit: these are owner/operator-reported field outcomes, not independently instrumented or audited validation at scale. Return-on-capital and profitability-per-hectare figures held in the source material are not promoted in this reference; the case rests on the measured water-level response.

ReferenceReported outcomeEvidence grade
Resting groundwater table reduction225 mmOwner/operator-reported field outcome
Open drain level reduction400 mmOwner/operator-reported field outcome
Shoulder-season pasture loss attributed to waterlogging before installation~30% from May-SeptemberGrower-reported video interview, 2025
Pasture harvest increase+4 tonnes dry matter per hectareOwner/operator-reported, not independently audited
Milksolids production increase+300 kilograms per hectareOwner/operator-reported, not independently audited

Limits and exclusions

This reference supports screening-level hydraulic checking only. The summary of findings is a navigation aid, not an exception to these limits. The following items remain outside the scope of the document and still require project-specific engineering review.

  • Crest vacuum margin, including atmospheric pressure, water temperature, vapour pressure, and pipe-profile elevation.
  • Pipe-class vacuum resistance and buckling under external load for the selected pressure class or SDR.
  • Pressure-pipe cases outside the turbulent screening envelope. The screening output preserves Swamee-Jain values inside the correlation range and marks the case when a custom input leaves it; either way, outside-envelope custom inputs require engineer review before design use.
  • Cases outside the published validity envelope. The calculator states a figure only inside the range the published matrices cover: the vertical spanned cannot exceed the route length, the water-level difference runs to 8 m, and the simplified gravity method holds to a 10% grade. On velocity, the published cells span up to 7.15 m/s and the calculator withholds above a registered ceiling of 7.2 m/s, which carries a small margin above the fastest published cell. Beyond any of those the numeric result is withheld rather than shown at a ceiling value, and the matched pump benchmark is withheld with the transfer figure it is derived from. These sites need project-specific engineering, not a screening number.
  • Pump curve matching, NPSH review, motor efficiency, drive efficiency, duty cycle, and system-curve intersection.
  • Primer-cycle capacity for site air ingress, restart conditions after dry periods, partial blockage, and operational reliability at commercial scale.
  • Design-grade rainfall-runoff hydrographs, time-of-concentration analysis, backwater profiles, downstream boundary-stage time series, and pump selection for tidal receivers and constrained outfalls.
  • Sediment handling, fouling, long-term roughness ageing, transient effects, water hammer, and surge.
  • Structural design of the primer manifold and all regulatory, consenting, discharge-quality, and land-access requirements.

References

  1. [1]Chow, V.T. (1959). Open-Channel Hydraulics.
  2. [2]NZS 4404 roughness coefficient preview.
  3. [3]Concrete Pipe Association of Australasia hydraulic design guidance.
  4. [4]Iplex Novadrain DWV pipe and fittings product information guide, SN4 mean internal diameter rows.
  5. [5]Marley Stormline SN4 stormwater product range.
  6. [6]Swamee, P.K., and Jain, A.K. (1976). Explicit equations for pipe-flow problems.
  7. [7]Iplex Poliplex polyethylene pressure pipe producer statement, SDR17 / PN10 mean ID rows.
  8. [8]PE100+ Association technical guidance.
  9. [9]Vinidex pressure-pipe vacuum and buckling guidance.
  10. [10]Cameron Hydraulic Data.
  11. [11]Karassik Pump Handbook.
  12. [12]WSA 03-2011 Water Supply Code.
  13. [13]Water Siphon calculation basis and matrix review record.
  14. [14]Water Siphon Ltd. Morelands Kaipara customer reference video, 2025.
  15. [15]DairyNZ managing pugging damage and winter pasture management extension material.
  16. [16]Beukes, P.C., et al. (2013). Evaluating the benefits of standing cows off pasture to avoid soil pugging damage in two dairy farming regions of New Zealand. New Zealand Journal of Agricultural Research, 56(3), 224–238.
  17. [17]Ballantine, D.J., & Tanner, C.C. (2013). Controlled drainage systems to reduce contaminant losses and optimize productivity from New Zealand pastoral systems. New Zealand Journal of Agricultural Research, 56(2), 171–185.
  18. [18]United States Environmental Protection Agency, EPANET documentation, EPANET 2.2 Analysis Algorithms covering Darcy-Weisbach friction regimes, Reynolds-number thresholds, minor losses, pumps, and pumping energy.
  19. [19]Humes NZ RCP and TITAN RP catalogue ranges.
  20. [20]Hynds NZ concrete and PE catalogue ranges.
  21. [21]Federal Highway Administration, Hydraulic Design Series No. 5: Hydraulic Design of Highway Culverts, outlet control and tailwater design framing.
  22. [22]United States Environmental Protection Agency, Storm Water Management Model Reference Manual Volume II — Hydraulics, dynamic runoff and hydraulic routing reference.
  23. [23]U.S. Army Corps of Engineers HEC-RAS Hydraulic Reference Manual, downstream stage-hydrograph boundary conditions for tidal or backwater environments.
  24. [24]MBIE. Acceptable Solutions and Verification Methods for New Zealand Building Code Clause E1 Surface Water, E1/VM1 Rational Method and runoff-coefficient context.
  25. [25]USDA NRCS Hydrology and Hydraulics tools, including WinTR-55 and WinTR-20 single-event watershed hydrology models.
  26. [26]Federal Highway Administration, Urban Drainage Design Manual Fourth Edition, Hydraulic Engineering Circular No. 22 (HEC-22), storm drainage and pump-station design framing.
  27. [27]NASA Glenn Research Center, Bernoulli equation assumptions and restrictions for steady, inviscid, incompressible flow framing.
  28. [28]NASA Glenn Research Center, Earth Atmosphere Model (metric units), troposphere temperature and pressure curve fits.
  29. [29]NIST Chemistry WebBook, Antoine equation parameters for water, Bridgeman and Aldrich (1964) coefficient set, 273–303 K.
  30. [30]IAPWS R12-08, Release on the IAPWS Formulation 2008 for the Viscosity of Ordinary Water Substance.
  31. [31]Boatwright, A., Hughes, S., & Barry, J. (2015). The height limit of a siphon. Scientific Reports, 5, 16790.
  32. [32]Hydraulic Institute, Engineering Data Library: Frictional Losses in Valves, Fittings, and Bends.
  33. [33]Tefera, K., Kandra, H., & Ma, J. (2021). CFD analysis of head losses in pipelines with butt fusion weld joints. Safety in Extreme Environments.
  34. [34]NIWA / Earth Sciences New Zealand, climate normals downloads 1991–2020: mean monthly air temperature and mean 10 cm earth temperature for selected New Zealand locations.
  35. [35]Toitū Te Whenua Land Information New Zealand, NZ 8m Digital Elevation Model (2012), interpolated from the 20 m contours of the Topo50 topographic map series. LINZ Data Service layer 51768, CC BY 4.0.

Engineering Reference — Version 2.2.0

This is the controlled web edition of the Water Siphon Engineering Reference. It is presented under the approved public brand, Siphonic Systems; that label does not assert the publishing legal entity. The reference supports method review and screening checks, not site-specific design.

Version
Version 2.2.0
Effective date
2 September 2026
Public brand
Siphonic Systems
Use
Engineering screening and method review
Access
Open web edition
Forwarding
May be forwarded; cite the canonical web address so readers receive the current edition
Edition
Current web edition
Supersedes
Version 2.1.0
Design status
Not for construction or procurement
Document enquiries

Method and edition questions go to Siphonic Systems; site-specific questions belong in a screening enquiry through the Site Calculator.

Contents

The reading sequence moves from decision context and defined terms through source authority, method, site boundaries, verification, matrices, evidence, and edition control.

  1. Summary of findings
  2. Scope and system definition
  3. Terms and symbols
  4. Source authority
  5. Method basis and three regimes
  6. Equations
  7. Inputs and assumptions
  8. Boundary conditions
  9. Worked example
  10. Sensitivity
  11. Verification
  12. Matrix interpretation
  13. Pipe matrices
  14. Field evidence
  15. Limits and exclusions
  16. References
  17. Document control

Figure register

Seven numbered figures are listed in reading order and cross-linked to their position in the reference.

  1. The 252 mm Water Siphon unit
  2. Three hydraulic calculation regimes
  3. Driving head and crest lift are separate checks
  4. Partial-flow sequence
  5. From stated inputs to a bounded screening result
  6. Positive, zero, and negative tailwater states
  7. Reynolds regime gate

Version history

2.2.0

Figures 2–7 redrawn as inline vector figures in the site diagram idiom; pipe-family matrices collapsed into expandable tables; document-control rows updated for the open web edition. Equations, matrix values, evidence qualifiers, and calculation authority are unchanged.

2.1.0

Reordered the controlled web edition around an engineer-first reading sequence and concise chapter navigation; equations, figures, matrices, evidence qualifiers, and calculation authority are unchanged.

2.0.0

Reordered technical narrative retained; added controlled metadata, numbered contents, seven-figure register, semantic engineering diagrams, and A4 print treatment.