All hot water systems must comply with the requirements of Building Regulation G3 in England, and to similar requirements in each of the devolved nations. However, due to a lack of updates to the guidance, many of the recommendations are now out of date, and causing issues for installers and specifiers. Without access to the most recent guidance the latest products may not be installed correctly.

A guide to G3 regulations

The G3 regulations contain many relevant and accurate points of reference for installers and industry professionals in England. This includes a mandatory requirement for all hot water systems (direct and indirectly heated, vented, unvented, storage, or instantaneous) to be:

• Resistant to the effects of temperatures and pressures occurring during normal use or any malfunctions of the system
• Compatible with systems that prevent any stored water from exceeding 100°C and, in the event of any discharge from safety devices, a means to visibly identify the discharge and safely contain and convey the discharge to a safe position.

G3 regulations also cover the provision of heated water to various locations in a property and the temperature safety controls on the delivery of hot water to baths and showers. 

These regulations and accompanying guidance in Approved Document G3 are freely downloadable from the government’s Building Regulations portal for use in industry practise: Sanitation, hot water safety and water efficiency: Approved Document G.

Time for change

While some of the G3 regulations still provide valid and accurate points of reference, the guidance notes contain a large amount of outdated information which has the potential to cause confusion. 

Originally written in 2010, with a revision in 2016, the regulations have not been updated recently, meaning there are now many incorrect references. It no longer reflects many current building practices, such as the use of plastic pipes, internal discharge systems, and newer ways of providing domestic hot water. 

Many of the references to British and European standards are either incorrect or out of date, which may lead to non-compliant installations due to installers or specifiers choosing incorrect materials and inappropriate practices. 

Suggestions for future guidelines

In an unvented (pressurised) hot water system, manufacturers are required by both G3 and Water Regulations to provide suitable components to control both inlet pressures, system expansion, and temperature to provide protection from over-pressure malfunctions. 

Guidance is given on the design and installation of the discharge system from any safety valve. However, this is not exhaustive and does not reflect many common practices. Guidance in this area needs updating both in terms of assessing the flow capabilities of the discharge system and the selection of materials. 

In addition to this, plastic pipes are allowed for use in a discharge system but there are incorrect references to suitable plastic pipe materials in the G3 guidance. The Hot Water Association (HWA) recommends that the British Plastic Federation Pipes Group guidance is read and followed to ensure suitable materials are selected. 

Finally, there are systems that can lower the temperature of any discharge, which could be as high as 90°C from a T&P Relief Valve, but they are not included in the G3 as they are recent industry innovations. As they are not mentioned or explicitly approved for this use, there is confusion as to their purpose and suitability. Manufacturers of these systems should be approached for further advice before commencing work.

Further guidance for industry professionals

Up to date industry guidance, such as Part G, is essential to ensure the latest products are installed correctly and that manufacturer instructions are based on a common approach underpinned by the latest guidance. 

If any deviation from the published G3 guidance is intended, manufacturers should first be consulted. Many manufacturers of equipment for hot water provision and ancillary components, such as safety valves, pressure and expansion controls, and hot water discharge, will have had their equipment assessed to the very latest standards.

It’s important that installers and specifiers keep in mind that the use of approved appliances or components does not automatically ensure a compliant system. It is the responsibility of installers to ensure the installation is wholly compliant with the requirements of G3 (and also Water Regulations where relevant). 

The current written guidance does not have to be followed if it can be demonstrated that the system employed meets the essential requirements of the regulation and is no less effective than the guidance. 

The HWA is advocating for a full revision of Building Regulation Part G, and G3, in particular, to correct these issues. In the short term, recognition from the government of the guidance’s shortcomings and the provision of additional advice in the FAQs section of the Building Regulation portal is being sought after.