Last edited 01 Apr 2021

Hot water safety



[edit] Introduction

Hot water is considered an essential building service. The two components of a typical hot water system are:

The water and pipework used for these two systems are not mixed, although both share some of the same components.

[edit] Hot water safety under Section G3 of Approved Document G

Section G3 of Approved Document G defines ‘domestic hot water’ as water that has been heated for cooking, food preparation, personal washing or cleaning purposes. Under Approved Document G, the “suitable installation for the provision of heated wholesome water or heated softened wholesome water” is required.

Section G3 provides specific guidance regarding hot water safety for sanitaryware (including washbasins, sinks, baths, showers and bidets) and other water storage systems (including cisterns or other water supply vessels). Under Section G3, systems should incorporate precautions to:

  • Prevent the temperature of the water stored in the vessel at any time exceeding 100C.
  • Ensure that any discharge from safety devices is safely conveyed to where it is visible but will not cause a danger to persons in or about the building.

Furthermore, the hot water supply to any fixed bath must be so designed and installed as to incorporate measures to ensure that the temperature of the water that can be delivered to that bath does not exceed 48C.

Section G3 provides specific information on additional areas, including


Design and installation of directly or indirectly heated hot water storage systems:

Safety devices:

Electric water heating

Solar water heating

Discharge pipes from safety devices:

Prevention of excessive temperatures

Prevention of scalding

Commissioning of fixed building services

Notice of completion of commissioning

[edit] Further guidance

In addition to the information in Approved Document G, further guidance for hot water storage system design and installation can be found in three British Standards Institution (BSI) documents:

[edit] Related articles on Designing Buildings Wiki

[edit] External resources

Designing Buildings Anywhere

Get the Firefox add-on to access 20,000 definitions direct from any website

Find out more Accept cookies and
don't show me this again