3 in schedule 40 pipe flow and volume calculator
3 in schedule 40 pipe has an outside diameter of 88.9 mm and a bore of 77.9 mm, a wall thickness of 5.50 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
- 113.317
- Inside diameter
- 77.90
- Wall thickness
- 5.500
- Bore area
- 4766.12 mm2
- Water content per metre
- 4.7661
- Water in the run
- 119.15
- Weight of that water
- 119.15
- Friction head loss
- 0.751
- Pressure drop
- 7.367 kPa
Show the working
- Flow velocity = 1.5
- Pipe run = 25
- Hazen-Williams C = 140
- Fluid density = 1000
- Inside diameter = 77.9 = 77.9
- outside = 88.9 = 88.9
- Wall thickness = (88.9 - 77.9) / 2 = 5.5
- Bore area = pi * 77.9^2 / 4 = 4766.12
- area_m2 = 4766.12 / 1e6 = 0.004 766 12
- Water content per metre = 4766.12 / 1000 = 4.766 12
- Water in the run = 4.766 12 * 25 = 119.153
- flow_m3s = 0.004 766 12 * 1.5 = 0.007 149 18
- Flow at that velocity = 0.007 149 18 * 60000 = 428.951
- Flow in US gallons per minute = 428.951 / 3.785411784 = 113.317
- loss_per_m = 10.67 * (0.007 149 18)^1.852 / (140^1.852 * (77.9/1000)^4.87) = 0.030 049
- Friction head loss = 0.030 049 * 25 = 0.751 225
- Pressure drop = 0.751 225 * 1000 * g0 / 1000 = 7.367
- Weight of that water = 119.153 * 1000 / 1000 = 119.153
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.
3 in pipe at common velocities
| Velocity (m/s) | Flow (L/min) | Flow (US gpm) |
|---|---|---|
| 0.5 | 143.0 | 37.77 |
| 1 | 286.0 | 75.54 |
| 1.5 | 429.0 | 113.32 |
| 2 | 571.9 | 151.09 |
| 2.5 | 714.9 | 188.86 |
| 3 | 857.9 | 226.63 |
Frequently asked
What is the inside diameter of 3 in schedule 40 pipe?
77.9 mm, against an outside diameter of 88.9 mm.
How much water does 3 in pipe hold?
4.766 litres per metre of run.
Where the numbers come from
- Dimensions are the ASME B36.10 schedule 40 values for the nominal size.