7.2 Special Locations & Bathroom Zones

BS 7671 Section 701: Rooms Containing a Bath or Shower

Within BS 7671 (The IET Wiring Regulations), certain areas are designated as 'Special Installations or Locations' because they pose an increased risk of electric shock. Section 701 deals specifically with locations containing a bath or shower.

The human body has a significantly lower electrical resistance when wet. If a person comes into contact with live electrical parts while wet and simultaneously in contact with earth (such as standing barefoot on a damp floor or touching conductive plumbing), the resulting electric shock is far more likely to be fatal. To mitigate this risk, Section 701 lays out stringent requirements regarding the zoning of the room, the Ingress Protection (IP) ratings of equipment, the use of Extra Low Voltage (SELV), and mandatory RCD protection.

Bathroom Zones Explained

To apply the regulations practically, a room containing a bath or shower is divided into three distinct zones—Zone 0, Zone 1, and Zone 2—based on the distance from the water source. The area outside these zones is generally referred to as 'outside the zones', though it is still part of the special location and subject to certain rules.

Zone 0

Zone 0 is the interior of the bathtub or shower basin itself. It is the area capable of holding water.

• Equipment: Only electrical equipment specifically designed for use in a bath or shower (such as specialized underwater lighting) can be installed here.
• Voltage: Equipment must be protected by Separated Extra-Low Voltage (SELV) with a nominal voltage not exceeding 12V AC or 30V DC.
• IP Rating: Equipment installed in Zone 0 must have a minimum Ingress Protection rating of IPX7, meaning it can withstand temporary immersion in water.

Zone 1

Zone 1 is the area directly above Zone 0. It is limited horizontally by the boundary of the bathtub or shower basin and vertically reaches a height of 2.25 meters from the finished floor level. If the shower head or water outlet is higher than 2.25m, Zone 1 extends to the height of the water outlet.

• Equipment: Permitted equipment includes water heaters, shower pumps, ventilation fans, and towel rails, provided they are suitable for the zone according to the manufacturer's instructions.
• Voltage: Like Zone 0, any equipment requiring a switch must be SELV (12V AC/30V DC), with the safety source located outside Zones 0 and 1.
• IP Rating: Equipment in Zone 1 must have a minimum rating of IPX4 (protection against splashing water). However, if the area is likely to be subject to water jets (e.g., for cleaning purposes), the requirement increases to IPX5.

Zone 2

Zone 2 extends 0.6 meters horizontally beyond the boundary of Zone 1, and up to a height of 2.25 meters from the finished floor level.

• Equipment: The equipment permitted in Zone 1 is also allowed in Zone 2, alongside luminaires (light fittings) and extractor fans.
• Voltage: SELV equipment is permitted.
• IP Rating: Equipment must have a minimum rating of IPX4 (or IPX5 if water jets are expected).

Outside the Zones

The space beyond Zone 2 is considered outside the zones. While the strict IP rating requirements relax here, it is still a bathroom environment. Equipment installed here must be suitable for the location, taking into account potential condensation and humidity.

Mandatory RCD Protection

One of the most critical safety measures introduced in modern editions of BS 7671 is the requirement for Residual Current Device (RCD) protection in bathrooms.

Every low voltage circuit serving a room containing a bath or shower must be provided with additional protection by an RCD having a rated residual operating current (IΔn) not exceeding 30mA.

This rule applies universally to:

• Lighting circuits.
• Shower circuits.
• Extractor fans.
• Heated towel rails.
• Any circuit passing through the bathroom, even if it does not serve any equipment within the bathroom (for instance, a cable running through the bathroom wall to supply a bedroom socket).

The 30mA RCD ensures that if a fault occurs and a person comes into contact with a live part, the supply is disconnected almost instantaneously (typically within 40 milliseconds at 5 times the rated current), preventing a fatal electric shock.

Socket-Outlets and Switches in Bathrooms

Traditionally, socket-outlets were strictly banned in UK bathrooms. While the regulations have relaxed slightly, they remain heavily restricted to ensure safety.

Socket-Outlets

Regular 230V socket-outlets (such as standard 13A plug sockets) are only permitted in a room containing a bath or shower if they are installed at least 3 meters horizontally from the boundary of Zone 1. Given the small size of most domestic bathrooms in the UK, this essentially means standard sockets are still rarely allowed.

The exceptions to this rule are:

• Shaver supply units: Complying with BS EN 61558-2-5, these incorporate an isolating transformer and can be installed in Zone 2 or outside the zones.
• SELV socket-outlets: Operating at 12V AC or 30V DC.

Switches and Controls

Any switch or control (such as a light switch) must be located so that it cannot be touched by a person using the bath or shower.

• In Zone 0, no switches are permitted.
• In Zone 1 and Zone 2, only switches for SELV circuits at 12V AC/30V DC are allowed.
• Pull-cord switches are permitted in Zone 1 and Zone 2, provided the pull-cord is made of insulating material and meets BS EN 60669-1.
• Standard 230V plate switches must be located outside the zones and out of reach of anyone in the bath or shower, which is why pull-cords or switches mounted on the outside of the bathroom door remain the standard practice in the UK.