2 1/2 in schedule 40 pipe flow and volume calculator
2 1/2 in schedule 40 pipe has an outside diameter of 73 mm and a bore of 62.7 mm, a wall thickness of 5.15 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
- 73.410
- Inside diameter
- 62.70
- Wall thickness
- 5.150
- Bore area
- 3087.63 mm2
- Water content per metre
- 3.0876
- Water in the run
- 77.19
- Weight of that water
- 77.19
- Friction head loss
- 0.968
- Pressure drop
- 9.489 kPa
Show the working
- Flow velocity = 1.5
- Pipe run = 25
- Hazen-Williams C = 140
- Fluid density = 1000
- Inside diameter = 62.7 = 62.7
- outside = 73 = 73
- Wall thickness = (73 - 62.7) / 2 = 5.15
- Bore area = pi * 62.7^2 / 4 = 3087.63
- area_m2 = 3087.63 / 1e6 = 0.003 087 63
- Water content per metre = 3087.63 / 1000 = 3.087 63
- Water in the run = 3.087 63 * 25 = 77.1907
- flow_m3s = 0.003 087 63 * 1.5 = 0.004 631 44
- Flow at that velocity = 0.004 631 44 * 60000 = 277.887
- Flow in US gallons per minute = 277.887 / 3.785411784 = 73.4099
- loss_per_m = 10.67 * (0.004 631 44)^1.852 / (140^1.852 * (62.7/1000)^4.87) = 0.038 703 4
- Friction head loss = 0.038 703 4 * 25 = 0.967 584
- Pressure drop = 0.967 584 * 1000 * g0 / 1000 = 9.488 76
- Weight of that water = 77.1907 * 1000 / 1000 = 77.1907
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.
2 1/2 in pipe at common velocities
| Velocity (m/s) | Flow (L/min) | Flow (US gpm) |
|---|---|---|
| 0.5 | 92.6 | 24.47 |
| 1 | 185.3 | 48.94 |
| 1.5 | 277.9 | 73.41 |
| 2 | 370.5 | 97.88 |
| 2.5 | 463.1 | 122.35 |
| 3 | 555.8 | 146.82 |
Frequently asked
What is the inside diameter of 2 1/2 in schedule 40 pipe?
62.7 mm, against an outside diameter of 73 mm.
How much water does 2 1/2 in pipe hold?
3.088 litres per metre of run.
Where the numbers come from
- Dimensions are the ASME B36.10 schedule 40 values for the nominal size.