Water Supply Industry Interpretations and Advice

  • Area of Interest : Installation
  • Topic : Water heaters
  • Title : Accommodation of thermal expansion
  • Clause Reference : Regulation 3 (2) & Schedule 2 paragraph 15 (2) (a)
  • Reference Number : I39
  • Decision Date : November 2013

In accordance with the provision made in Schedule 2 paragraph 15 (2) (a) expanded water from a water heater with a capacity of less than 15 litres is permitted to backflow into a supply pipe providing that this does not cause the temperature of the water in the supply pipe to exceed 25°C. As it is not permissible for water displaced as a result of accommodating this expansion to backflow into the communication pipe systems must be designed and installed to accommodate both expanded water plus any water this displaces within the supply pipe.