Pipe Volume Calculator
Watch the velocity, not just the volume.
Work out Pipe Volume. Watch the velocity, not just the volume. Free, with no account and nothing to install.
Pipe contents
3.801 litres
0.53 m/s at 12 L/min
Volume is straightforward — area times length — but it is the velocity that decides whether a pipe run is any good. Halving the diameter quarters the area and quadruples the velocity at the same flow, which is how undersized pipework becomes noisy. Water weighs a kilogram a litre, so pipe contents matter for filling and draining systems and for the load on supports in long horizontal runs. A 28 mm pipe holds about 0.6 litres a metre, which adds up quickly across a heating circuit. Copper pipe is sized by outside diameter and plastic by nominal bore, so a 22 mm copper pipe and a 22 mm plastic one do not have the same internal area. Use the actual internal figure, which is on the manufacturer's data sheet rather than the label.
How the Pipe Volume Calculator works
Volume, weight and flow velocity for a pipe run. Velocity decides whether pipework is quiet and long-lived, and it is what sizing by volume alone ignores.
Also known as: how much water is in my pipes · litres per metre of 22mm pipe · why is my pipework noisy · flow velocity in a pipe
Frequently asked questions
How much water does a pipe hold?
A 22 mm bore holds about 0.38 litres per metre and a 15 mm about 0.18. Across a heating circuit that adds up quickly, which matters for filling, draining and dosing inhibitor.
What flow velocity is acceptable?
Below about 1.5 m/s for domestic pipework. Above that it becomes audible, and above roughly 2 m/s erosion of copper accelerates sharply on hot water.
Is 22 mm copper the same bore as 22 mm plastic?
No. Copper is sized by outside diameter and plastic often by nominal bore, so the internal areas differ. Use the manufacturer's internal figure rather than the label.
Why does halving the diameter matter so much?
Area goes with the square of diameter, so halving it quarters the area and quadruples the velocity at the same flow. That is how undersized pipework becomes noisy.
How long does a pipe run take to fill?
Volume divided by flow rate. It is worth knowing for commissioning, because air removal takes far longer than filling and is what most cold radiators come down to.
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