Thermal Expansion / Contraction of PVC is roughly 4.5 to 5 times more than metallic pipes. As long as UPVC pipes are concealed, thermal changes do not have any adverse effect on its performance. But in case of exposed lines and for fluid temperature above ambient, effect of thermal expansion & contraction needs to be considered.

The change in length of pipeline can be calculated as:

l = § x L x t

l :

Change in length in mm

§ :

Coefficient of linear thermal expansion / contraction of PVC (6.4X10-5mm/mm/ 0C).

L :

Length of pipe in mm (in ambient temperature)

T :

Difference between ambient temperature & maximum service temperature


To accommodate this thermal expansion and contraction, followi

Expansion Loop : The most common method used to compensate for changes in the pipe line

x = 1.44 x d x l

d :

Outside diameter of the pipe

I :

Change in length in mm


Recommended distance between supports in meters :


Support spacing are a function of pipe size operating temperatures, the location of heavy valves or fittings and the mechanical properties of the pipe material.
All piping should be supported at interval sufficiently close to maintain correct pipe alignment and to prevent sagging or geade reversal. Pipe should also be supported at all branch ends and at all changes of direction.
NOTE: The above information provides general guidelines. It should be used only as a reference and not as a guarantee of performance. Specific installation instructions and techniques may be required as a result of local plumbing and building codes, engineering specifications and instructions.


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