Pipe sizing and friction loss calculators
Irrigation pipe sizing and friction loss
Compare true internal bores, calculate velocity and account for both pipe and fitting losses.
Read the worked example
Friction Loss (Hazen-Williams)
Pipe hydraulics: sizing, flow and friction loss
Calculate pipe flow, velocity and friction loss, then check the pressure available to the system. Explore pipe hydraulics tools for irrigation designers, pump retailers and engineers.
Choose a calculation or design guide
Read a public example, check the required inputs, or explore a calculator. New accounts require approval; start a 14-day free trial.
Guides & worked examples
Understand the calculation
Follow the inputs, equations and assumptions before working on a project design.
Watch
Civil & hydraulics in Tenselo
A short introduction to what Tenselo covers in this category.
Video summary: Flow, velocity, pipe volume, Darcy-Weisbach and Hazen-Williams friction loss, fittings, elevation and preliminary pipe selection.
Result preview
Friction & head-loss result
Hazen-Williams · PE/PVC/steel
This abbreviated result preview omits some design inputs. Use the linked worked examples for reproducible arithmetic; review the complete inputs, product data and warnings for a project design.
Inputs
Flow
15.0 L/s
Pipe
DN125 PE100
Length
500 m
Fittings allowance
50 m
Results
1.66 m
Loss / 100 m
9.12 m
Total head loss
89.4 kPa
Pressure drop
1.27 m/s
Velocity
0.89 bar
= bar
550 m
Equivalent length
Why it matters on the job
Velocity in the safe band
Keeps flow fast enough to self-clean, slow enough to dodge erosion and surge.
Real head loss, real pressure
Hazen-Williams loss in m, kPa and bar — so pump head and class selection are defensible.
Review transient conditions
Surge and column-separation tools flag the risk before it cracks a main.
What a pipe hydraulics calculation needs
Pipe hydraulics describes how flow, velocity, pressure and elevation interact in a pipe system. Start with the operating flow and the actual internal diameter, calculate losses along the route, and check the pressure available at the critical outlet.
Head and pressure are related, but not interchangeable
Pressure head is p/(ρg): pressure p divided by fluid density ρ and gravitational acceleration g. For water at an assumed density of 1,000 kg/m³ with g = 9.81 m/s², one metre of pressure head is 9.81 kPa. Elevation head also belongs in the energy balance; an uphill route requires more supply head than the same route on level ground.
Use the right diameter and loss method
Nominal size is a product designation; it may differ from the internal bore used in a calculation. The worked pipe-sizing example compares 100 mm and 125 mm internal bores at 10 L/s, showing velocity, Darcy–Weisbach loss and fitting loss separately. Its assumed friction factor is for arithmetic comparison, not a product selection.
A mainline and a drip lateral carry different flow profiles
A constant-flow mainline carries the full design flow throughout. Flow falls after each emitter along a drip lateral, so losses need to reflect each segment's flow. See the segmented drip-lateral example before applying a full-flow mainline result to emitting pipework.
Complete the system check
Combine pipe, fitting and equipment losses with elevation and the required outlet pressure. Review operating cases, maximum pressure and transients separately. Low steady-state loss does not establish protection against water hammer. Carry the assessed flow and head into pump sizing.
HYD-009 + HYD-012 · worked example
Pipe volume, flow rate and velocity calculators
Use this pipe volume calculator example to find stored water and ideal fill time, then relate the same 100 mm actual internal bore and 10 L/s duty to flow rate and pipe velocity.
Design questionWhat happens inside a 500 m main at 10 L/s?
- Internal diameter
- 100 mm
- Pipe length
- 500 m
- Flow
- 10 L/s
Calculated result. At 10 L/s, water travels through the 100 mm bore at 1.273 m/s. The pipe stores 7.85 L/m, or about 3,927 L over 500 m, with an ideal volume-divided-by-flow fill time of 6.5 minutes.
Calculation sequence
- Area = πD²/4, using D = 0.100 m, giving 0.00785 m² or 7,853.98 mm².
- Velocity = flow/area, using 10 L/s = 0.010 m³/s.
- Stored volume = area × 500 m; ideal fill time = volume/flow.
This static, hypothetical example was run in Tenselo HYD-009 and HYD-012 on 15 September 2026. Live project calculations and PDF reports require authorised application access.
Pipe volume, flow rate and friction loss calculator questions
What pipe hydraulics calculations are in Tenselo?
Tenselo includes pipe volume and fill-time, flow and velocity, Darcy-Weisbach and Hazen-Williams friction-loss, fitting-loss, elevation, surge, air-valve, preliminary pipe-selection and water-meter sizing calculations.
How does a pipe volume calculator work?
It uses the actual internal diameter and pipe length to calculate cross-sectional area and stored volume. Dividing stored volume by steady flow gives an ideal fill-time check; real filling also depends on air release, pump duty, friction and pressure.
How is a flow rate calculator different from a pipe velocity calculator?
Flow rate is the volume moving per unit time, while velocity is the water speed inside the pipe. They are connected by Q = A x v, so the actual internal diameter is required when converting between them.
What does a friction loss calculator need?
It needs the flow, actual internal diameter, pipe length and the selected loss method. Material roughness or Hazen-Williams C value, water properties, fittings, elevation and equipment losses may also be required for the complete system check.
Can I use the pipe hydraulics calculators now?
The website provides public guides and static worked examples. Apply for an account to run project calculations; new applications require approval.
Choosing pipe hydraulics software
Confirm the friction method, diameter convention, operating cases and required outputs. The software selection guide explains how to evaluate metric calculations and reports alongside any CAD or network modelling requirements.
A 650 m supply main at 34 L/s
View the worked sample and downloadable PDF for the inputs, calculation result, manufacturer references and limitations.
Water meter sizing calculator
HYD-029, Water Meter Sizing, supports water-system designers assessing meter size, flow range and installation straight lengths from the operating flow, pipe size and selected technology. It also provides indicative brand and output options for review.
Start with the flow duty
Record the normal operating flow and check the expected low and peak flows. The pipe's nominal diameter alone is not a meter selection. Review the candidate meter's rated flow range, pressure loss, water conditions and installation requirements against the current manufacturer data.
Check meter technology and installation
The calculator includes mechanical and static-meter options. Its size and straight-length guidance supports preliminary selection; confirm the exact model, orientation, upstream fittings, available straight pipe and any required pattern approval with the supplier. Different instruments can have different installation requirements even when their nominal size matches.
Choose the readout and check pulse scaling
Establish whether the project needs a local register, pulse output or communications. For a pulse-output meter, use the flowmeter K-factor and pulse-scaling calculator to convert frequency to flow or a pulse count to volume. Match the K-factor units to the meter configuration and the receiving counter.
The flowmeter straight-length check considers the meter type and upstream disturbance. Use these calculations with the supplier's model-specific instructions. New accounts require approval; running project calculations requires authorised application access. See availability and registration.
What is in this category
31 Pipe Hydraulics calculators
Every calculator in this category, by its reference code. Running them requires an approved Tenselo account with access to the relevant calculators.
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HYD-001 Pipe Insulation Heat Loss
Heat loss & surface temperature of an insulated (and bare) horizontal pipe
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HYD-002 Siphon Priming / Break-Vacuum
Crown vacuum, cavitation/air-break check and priming volume for a siphon pipeline
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HYD-003 Flange Finder
AS 4087 / AS 2129 / ANSI / ISO drilling: OD, PCD, bolts, holes
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HYD-004 HDPE Butt Weld Fusion (Tender)
Fusion pressures + times and a joint-count / crew / days estimate
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HYD-005 Pipe DN from Friction
Smallest DN whose total HW loss <= your budget
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HYD-006 Pipe PN Selector
Smallest pressure class covering operating + surge
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HYD-007 Pipe Selector (AU)
Fluid + flow + velocity -> recommended pipe (viscosity-aware Darcy-Weisbach)
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HYD-008 Pipe Size Recommendation
Smallest standard DN that meets your target velocity
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HYD-009 Pipe Volume & Fill Time
Water held in a pipe run and the time to fill or drain it at a flow
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HYD-011 Trench Excavation Volume
Dig, bedding and spoil volumes for a pipe trench (with batter)
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HYD-012 Flow & Velocity
Pipe area, velocity, flow conversions
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HYD-013 Friction (Darcy-Weisbach)
Alternative to Hazen-Williams for non-water or high-precision
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HYD-014 Friction Loss
Pipe head loss + fittings allowance
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HYD-015 Gravity Flow
Gravity flow for an AU pipe (check OR size for a flow) + vacuum-collapse + air valves
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HYD-016 Manifold Head Loss
Even-spaced outlets along a header
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HYD-017 Minor Losses (K factors)
Fitting head loss h_L = K * v^2 / 2g
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HYD-018 Reynolds Number
Laminar vs turbulent
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HYD-019 Velocity Head
H_v = v^2 / 2g
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HYD-020 Manning Open Channel
Flow in an open channel
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HYD-021 Orifice Discharge
Flow through a sharp-edged orifice from its diameter + head
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HYD-022 Slide Gate Flow Estimator
Flow under a sluice / slide gate lifted off the bottom (L/s + ML/day)
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HYD-023 Tank Drain Time (Orifice)
Time to gravity-drain a tank through an outlet orifice
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HYD-024 Weir Flow Estimator
Channel / spillway flow over a rectangular weir (L/s + ML/day)
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HYD-025 Bracket / Support Spacing
Max support spacing AND the load each support carries, for an above-ground pipe full of water
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HYD-026 Thermal Expansion
Pipe growth/shrink, expansion-loop leg and anchor force vs temperature
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HYD-027 Thrust Block Size Calculator
Bend/tee/cap thrust -> bearing area, block size & concrete volume
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HYD-028 Water Hammer / Surge Anticipation
Surge on valve closure + static head -> total at the valve
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HYD-029 Water Meter Sizing
Size the meter + straight pipe lengths by flow & pipe size; pick a brand/output
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HYD-030 Water Supply & Fire-Flow Demand
Peak day/hour demand + fire flow & storage, governing main size (WSA 03 / AS 2419.1)
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HYD-031 Screen Flow Selector
Flow through intake & process screens: open area, screen area, velocity checks and head loss for wedge-wire, sidehill, suction, drum and well screens
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HYD-032 Anti-Vortex Plate Design
Size an anti-vortex plate for a foot valve / pump in shallow water, or a tank outlet to recover dead storage
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