Resistance to thermal expansion

Last updated on Wed, 02/09/2011 - 10:01

Most solids expand when they are heated and are liable to elongate under temperature increase.
For pipe systems made of materials that are subjected to high levels of thermal expansion, precautions have to be taken at design stage.
Cast iron expands very little and does not require specific bracketing nor expansion collars. It makes the specifers’ design work easier and avoids extra cost at installation stage.

Thermal expansion coefficient of cast iron and other materials

The thermal expansion coefficient for cast iron – 0.01 mm/m/°C – is very low and very similar to that of steel and concrete; the building and the pipe systems will move and will expand together.

Thermal expansion of cast iron and other materials for a temperature rise of 50°C and 10m.


For cast iron, the bracketing system is designed to only carry the weight of the pipe and its content, which makes the designers work easier.
Plastic pipes, for themselves, expand considerably with increasing temperature. Their bracketing system must be designed and adapted accordingly, as it can deeply affect the stability of a pipework and its performances over time.

Thermal expansion of plastics

To allow expansion without damaging the drainage network, plastic pipe systems demand specific accessories – expansion collars or joints, brackets allowing axial movement, in general one of the two brackets described.
If these precautions were not taken, expansion could be absorbed by the pipework and cause distortion.

Cast iron can do without these expensive accessories. It makes the design work easier and decreases the risk of mistakes at installation stage.

These properties of cast iron pipe systems are also valuable for engineering structures such as bridges where important expansions have to be carefully addressed to secure the construction project.