Boilers and bathrooms

Gas Safe Register’s Technical Team review the requirements and regulations that apply on those occasions when it’s necessary to fit a boiler in a bathroom.
This is an abridged version of the article in May/June 2024’s Registered Gas Engineer’s magazine.

Gas appliances should only be installed in a room or space containing a bath or shower if there is no other practical location and must only be installed in a safe location away from sources of water. Where this is necessary, boilers or other gas appliances must be room-sealed.

As well as following the manufacturer’s installation instructions carefully, you should take regard of what’s set out in the Gas Safety (Installation and Use) Regulations 1998, Regulation 30 of which prohibits the installation of certain gas appliances in specified rooms, stating: “No person shall install a gas appliance in a room used or intended to be used as a bathroom or shower room unless it is a room-sealed appliance.”

This requirement extends to rooms that contain a bath or shower but that may not have been purpose-built as a bathroom or shower room. This is because a gas appliance is burning the fuel to heat hot water, there is a possibility it will use up the air in that room if it is an open-flued or flueless appliance. It’s essential that the gas appliance is room-sealed so as to prevent any starvation of air in that room, or products of combustion.

The prohibition on installing open-flued or flueless appliances also extends to any cupboards or compartments that are accessed from the bathroom/shower room, and cupboards or compartments that may have air vents or openings connected to that space.

The requirements of Regulation 30 are further expanded in Technical Bulletin 034, which describes how the regulations have evolved to reflect the changes in Building Regulations, technology and different types of appliance that are used today.

Electrical safety
Technical Bulletin 119 gives guidance on another important requirement: electrical safety. As well as the gas appliance only being installed in a safe location away from water, the controls for the appliance must be adequately IP-rated for use in that zone. These zones are fully described in Technical Bulletin 119.

The electrical circuits in this location shall also be provided with additional protection by a residual current device (RCD) that does not exceed 30 mA, with an operating time not exceeding 40 ms. Electrical components in the bath/shower room should also be RCD-protected: this includes low-voltage lighting circuits, shower circuits, bathroom heaters, electric towel rails and, of course, central heating boilers.

Technical Bulletin 119 also describes where and when local supplementary equipotential bonding is required to metallic water and gas pipes and other bathroom components.

What is an IP code?
An IP code is an Ingress Protection code. It’s a classification code system that details the level of protection against solids and liquids. Before installing any room-sealed appliance in a bathroom, the manufacturer’s instructions must be consulted. These will detail the appliance IP rating and give guidance on which zone is suitable for installation: generally this is beyond Zone 2.

Zones in locations containing a bath or shower
Illustration indicating electrical safety zones in a bathroom

• Gas Safety (Installation and Use) Regulations 1998

Technical Bulletin 034: Open-flued appliances in bathrooms, a potted history
Technical Bulletin 119: Electrical safety requirements for gas appliances installed in locations containing baths or showers
BS 7671:2018 Requirements for electrical installations IEE Wiring Regulations – 18th edition|
BS EN 60529:1992 Degrees of protection provided by enclosures (IP Code)