5 in schedule 40 pipe flow and volume calculator
5 in schedule 40 pipe has an outside diameter of 141.3 mm and a bore of 128.2 mm, a wall thickness of 6.55 mm. Nominal pipe size is a label, not a measurement — nothing about a 1-inch pipe is one inch.
Domestic water is usually kept between 1 and 2.4 m/s to limit noise and erosion.
Copper and plastic about 140; new steel 130; old steel 100.
- Flow in US gallons per minute
- 306.899
- Inside diameter
- 128.20
- Wall thickness
- 6.550
- Bore area
- 12 908.21 mm2
- Water content per metre
- 12.9082
- Water in the run
- 322.71
- Weight of that water
- 322.71
- Friction head loss
- 0.420
- Pressure drop
- 4.121 kPa
Show the working
- Flow velocity = 1.5
- Pipe run = 25
- Hazen-Williams C = 140
- Fluid density = 1000
- Inside diameter = 128.2 = 128.2
- outside = 141.3 = 141.3
- Wall thickness = (141.3 - 128.2) / 2 = 6.55
- Bore area = pi * 128.2^2 / 4 = 12 908.2
- area_m2 = 12 908.2 / 1e6 = 0.012 908 2
- Water content per metre = 12 908.2 / 1000 = 12.9082
- Water in the run = 12.9082 * 25 = 322.705
- flow_m3s = 0.012 908 2 * 1.5 = 0.019 362 3
- Flow at that velocity = 0.019 362 3 * 60000 = 1161.74
- Flow in US gallons per minute = 1161.74 / 3.785411784 = 306.899
- loss_per_m = 10.67 * (0.019 362 3)^1.852 / (140^1.852 * (128.2/1000)^4.87) = 0.016 809 9
- Friction head loss = 0.016 809 9 * 25 = 0.420 248
- Pressure drop = 0.420 248 * 1000 * g0 / 1000 = 4.121 22
- Weight of that water = 322.705 * 1000 / 1000 = 322.705
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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The formula
- bore area = pi d^2 / 4
- flow = area x velocity
- Hazen-Williams head loss per metre = 10.67 Q^1.852 / (C^1.852 d^4.87), SI units
Nominal pipe size is a legacy label. Above 14 inch NPS the outside diameter equals the nominal size; below it, neither dimension matches.
Hazen-Williams is an empirical formula fitted to water near room temperature. For other fluids or for gases, use Darcy-Weisbach.
Fittings add loss too. A rule of thumb is to add 30 to 50% to the straight-run figure for a typical domestic circuit.
5 in pipe at common velocities
| Velocity (m/s) | Flow (L/min) | Flow (US gpm) |
|---|---|---|
| 0.5 | 387.2 | 102.30 |
| 1 | 774.5 | 204.60 |
| 1.5 | 1161.7 | 306.90 |
| 2 | 1549.0 | 409.20 |
| 2.5 | 1936.2 | 511.50 |
| 3 | 2323.5 | 613.80 |
Frequently asked
What is the inside diameter of 5 in schedule 40 pipe?
128.2 mm, against an outside diameter of 141.3 mm.
How much water does 5 in pipe hold?
12.908 litres per metre of run.
Where the numbers come from
- Dimensions are the ASME B36.10 schedule 40 values for the nominal size.