Pipe Thermal Expansion Calculator

Give it the length of the run, the material and the two temperatures. It returns the movement in millimeters and inches, per 10 meters and per 100 feet, so you can size the loop or the offset before the run is closed in.

Run length

The straight length between the two things holding the pipe still, anchor to anchor, not the whole system.

Length unit

The unit you measured the run in.

Pipe material

Each option below states the exact coefficient it uses. If your datasheet says something else, use it: pick "Enter my own".

Temperature when installed

What the pipe was at when it was fixed in place. A line clipped in an unheated basement in February starts colder than you think.

Temperature in service

What it reaches in use. Take the far end of the range, not the average: that is where the movement is.

Temperature unit

Applies to both temperatures above. Enter each one as a reading, not as a difference: the difference is worked out here.

Result

Fill in a few more boxes and the answer will show here.

Opens your print dialog. Choose Save as PDF. Your figures stay on this device.

Loading the calculator.

This is a general measurement calculator. Confirm dimensions, product coverage and job requirements before ordering or installing materials.

How far a run really moves

Pipe changes length with temperature, and the amount is set by three things: how long the run is, how far the temperature swings, and what the pipe is made of. Movement is straight-line in the first two: double the length or double the swing and you double the travel. The third is the coefficient of linear expansion, a published property of the material, and it is the reason a plastic hot line moves several times as far as a copper one beside it.

The swing is where this goes wrong. A temperature and a change in temperature do not convert the same way between the two scales. A reading converts with the offset, so 68 degrees Fahrenheit is 20 Celsius. A change converts by the ratio alone, so a 72 degree Fahrenheit swing is a 40 degree Celsius one. Subtract 32 from a swing and you get roughly a third of the real movement, on the comfortable side. Enter both temperatures here as readings and the difference is worked out for you.

Read the answer as travel that has to go somewhere. A run free at one end just slides. A run anchored hard at both ends cannot, so the same movement becomes force. It bows between clips, rubs where it crosses a joist, and ticks in the ceiling every time the boiler fires. The per 10 meters and per 100 feet figures are there so you can size a loop or an offset on the spot.

The common mistake is using the day you installed it as the cold end of the range. Zeus keeps the job history for an address, so a run that ticked in the ceiling last winter is on the record before anyone opens the wall to look for it.

Built for Plumbing work: see the Plumbing job app.

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