6 in schedule 40 pipe flow and volume calculator
6 in schedule 40 pipe has an outside diameter of 168.3 mm and a bore of 154.1 mm, a wall thickness of 7.10 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
- 443.429
- Inside diameter
- 154.10
- Wall thickness
- 7.100
- Bore area
- 18 650.70 mm2
- Water content per metre
- 18.6507
- Water in the run
- 466.27
- Weight of that water
- 466.27
- Friction head loss
- 0.339
- Pressure drop
- 3.325 kPa
Show the working
- Flow velocity = 1.5
- Pipe run = 25
- Hazen-Williams C = 140
- Fluid density = 1000
- Inside diameter = 154.1 = 154.1
- outside = 168.3 = 168.3
- Wall thickness = (168.3 - 154.1) / 2 = 7.1
- Bore area = pi * 154.1^2 / 4 = 18 650.7
- area_m2 = 18 650.7 / 1e6 = 0.018 650 7
- Water content per metre = 18 650.7 / 1000 = 18.6507
- Water in the run = 18.6507 * 25 = 466.268
- flow_m3s = 0.018 650 7 * 1.5 = 0.027 976 1
- Flow at that velocity = 0.027 976 1 * 60000 = 1678.56
- Flow in US gallons per minute = 1678.56 / 3.785411784 = 443.429
- loss_per_m = 10.67 * (0.027 976 1)^1.852 / (140^1.852 * (154.1/1000)^4.87) = 0.013 563 9
- Friction head loss = 0.013 563 9 * 25 = 0.339 098
- Pressure drop = 0.339 098 * 1000 * g0 / 1000 = 3.325 41
- Weight of that water = 466.268 * 1000 / 1000 = 466.268
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.
6 in pipe at common velocities
| Velocity (m/s) | Flow (L/min) | Flow (US gpm) |
|---|---|---|
| 0.5 | 559.5 | 147.81 |
| 1 | 1119.0 | 295.62 |
| 1.5 | 1678.6 | 443.43 |
| 2 | 2238.1 | 591.24 |
| 2.5 | 2797.6 | 739.05 |
| 3 | 3357.1 | 886.86 |
Frequently asked
What is the inside diameter of 6 in schedule 40 pipe?
154.1 mm, against an outside diameter of 168.3 mm.
How much water does 6 in pipe hold?
18.651 litres per metre of run.
Where the numbers come from
- Dimensions are the ASME B36.10 schedule 40 values for the nominal size.