10 Pipework Expansion
Consideration for design and installation
All pipework will expand and contract longitudinally and around the circumference when subjected to temperature variations.
The temperature variations can occur as a result of fluids within the pipework being heated or cooled, or from the effects of external heat sources, such as the surrounding air temperatures, solar heat, etc.
The temperature variations can range from gradual, such as the increase and decrease in room air temperatures, to almost instantaneous, such as when hot water is discharged from a sanitary fitting, or when heated water is suddenly circulated through the pipework.
Generally the change in diameter of pipework used for Building Services Engineering will not require detailed consideration, other than to ensure that adequate clearances are maintained between pipes, pipe supports, joists, building structures, etc, to allow free movement of the pipework.
The expansion and contraction along the length of pipework can however be very significant, particularly for steam, condensate, heating, domestic hot water and certain waste pipework installations. Expansion and contraction within cold water pipework systems is minimal and generally does not require any special consideration.
It should be noted that the rate of expansion and contraction varies as a result of the type of material, as well as the temperature variation. PVC pipework, for instance, will expand at over three times that of copper, for the same temperature rise.
Damage and failure from stress and strain can occur to pipework systems, pipework support systems and building structures unless careful consideration is given to the change in pipework length due to temperature change and the direction in which the expansion and contraction will take place.
Compiled and published by: The Institute of Plumbing
Last revision: 2002
Number of pages: 6