Safety notice to act as a reminder of the phenomenon of condensate induced water hammer


Following an incident currently being investigated by the Office for Nuclear Regulation, the Health and Safety Executive (HSE) is issuing a safety notice to remind duty-holders about condensate induced water hammers.

Water hammer is a known vulnerability in steam systems, and sometimes is referred to as ‘Condensate Induced Water Hammer’, which occurs when steam is introduced into cold pipe-work that has not been sufficiently drained. As the steam cools, it condensates and takes up less volume in the pipework than steam, which produces a vacuum, creating an impact against the pipework.

Dutyholders have a number of responsibilities under the Pressure Systems Safety Regulations 2000 in England, Wales and Scotland. Dutyholders should ensure suitable measures are taken to prevent the occurrence of such events, including the appropriate operation and maintenance of systems on their sites.

The HSE recommends that the 5 point action plan detailed in the Safety Assessment Federation factsheet; ‘potential hazards created by water hammer in steam systems’ is considered. This includes taking into account the following:

  • Enhanced training of boiler operators
  • Slope of pipework and drainage
  • Positions where condensate could collect
  • Operation of traps
  • Isolation valves


The Safety Assessment Federation factsheet can be viewed here.