Water Supply Industry Interpretations and Advice

  • Area of Interest : Installation
  • Topic : Expansion vessels
  • Title : Installation of expansion vessels
  • Clause Reference : Regulation 3 (2)(i)
  • Reference Number : I20
  • Decision Date : September 2007 (Revised April 2013)

In recognition that water stagnation and particulate accumulation can have detrimental effects upon water quality it is recommended that any fitting on a wholesome water system which accommodates expansion or pressure surges, such as expansion vessels, pressure accumulators and surge arrestors, be installed so as to avoid localised low turnover (stagnation) leading to the formation of biofilms and/or the accumulation of particulates. That is to say be installed in the vertical so that the fitting accommodating thermal expansion or a pressure surge is:-

    1. bottom fed and upright; and
    2. that the connecting pipework to the fitting:-
        - rises continuously; and
        - is kept to a minimum; and
    3. sized correctly for the system; and
System design
    4. designed to ensure an adequate turnover of water within the fitting.