Hot water safety

[edit] Introduction

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

• The central heating system which supplies hot water to radiators located around a building.
• Domestic hot water supplied to taps and sometimes to appliances.

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

Guidance:

• Performance
• General
• Provision of hot water supply

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

• General
• Vented hot water storage systems
• Unvented hot water storage systems – all systems
• Unvented hot water storage systems – systems up to 500 litres capacity and 45kW power input
• Unvented hot water storage systems – systems over 500 litres capacity or over 45kW power input

Safety devices:

• Non-self-resetting energy cut-outs
• Temperature and pressure relief devices

Electric water heating

Solar water heating

Discharge pipes from safety devices:

• Discharge pipe D1
• Tundish
• Discharge pipe D2
• Termination of discharge pipe

Prevention of excessive temperatures

Prevention of scalding

• Installation

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:

• BS EN 806-5:2012 Specifications for installations inside buildings conveying water for human consumption. Operation and maintenance.
• BS 8558:2015 Guide to the design, installation, testing and maintenance of services supplying water for domestic use within buildings and their curtilages.
• BS EN 12897:2006 Water supply.

[edit] Related articles on Designing Buildings

• A guide to installing thermostatic mixing valves: what, why and how.
• Approved Document G.
• Building services.
• Hot water.
• Hot water safety in health and social care settings.
• Plumbing.
• Stagnation point.
• Tap.
• Water heating.

[edit] External resources

• BSI, BS EN 806-5:2012 Specifications for installations inside buildings conveying water for human consumption. Operation and maintenance.
• BSI, BS 8558:2015 Guide to the design, installation, testing and maintenance of services supplying water for domestic use within buildings and their curtilages.
• BSI, BS EN 12897:2006 Water supply.
• Gov.uk, Approved Document G.