Electrical Regulations in UK Bathrooms

This article uses the brown book of the Electrical Regulations BS:7671 amendment 2, 18th edition and page numbers referenced in this book. There are some small changes between the Amendments and we cover the relevant ones here on pages 245 and 246, but they can still be confusing. We will describe to you in a little more detail the important parts that you need to understand and hope that we make the points much more clearly.

Bathroom Zones Overview

Definition of Zones

So let’s look at just what the zones are in a bathroom. The zones have particular dimensions for the safety of the user.

Significant Measurements

What are the significant measurements? There is a height requirement common to all zones. Horizontally along the floor, we have Zone 0 and Zone 1 where the bathtub sits with quite strict rules. Then there is Zone 2 where the rules relax slightly and finally an area called outside the zones with a further reduction in requirements.

Conceptual View

Think of the inside of the bathroom as a set of boxes. There is a box that surrounds the outside dimensions of the bath and another box that starts from the edge of the bath. The highest requirement is 2.25 meters; however, if the shower head or other water outlet exceeds this height then the height requirement increases with it.

Detailed Zone Descriptions

Zone 0 and Zone 1

Let’s take a look at Zone 0 and Zone 1:

• Zone 0 is the space inside the bathtub. Think of Zone 0 as where the water goes right to the top of the bathtub.
• Zone 1 is the space above and below the bathtub that is not Zone zero. Remember this includes the area under the bathtub unless something else happens.

Changes Under the Bathtub

Things can change under the bathtub. If the bathtub is against a wall on one side and a bath panel has also been installed. If the bath panel requires a tool (a screwdriver for example) or a key to remove it, then the space under the bath is classed as being outside the zones and not Zone one.

Zone 1 Border

We must understand the Zone 1 border. It can confuse and often appears in exam questions as is so easy to get wrong. Zone 0 is inside the bathtub, but Zone 1 is the outside edge of the bathtub and with most bathtubs that can be a difference of 50 millimetres or more.

Bathroom Floor Space

Now we can look at the bathroom floor space. Take note that there is no Zone 3 in a bathroom – another exam favourite to catch you out. There are two zones, both start from the outside edge of the bathtub. They start from the edge of Zone 1, not Zone 0. This box will extend along the floor to a distance of 2.5 meters from Zone 1.

Zone 2

We can begin with examining zone 2. This is the space up to 0.6 meters from the edge of the bath from the edge of Zone 1. Notice there is no mention of Zone 0.

Outside the Zones

Then we have a space called outside the zones. Again, this is measured along the floor from the edge of the bathtub but only takes effect where Zone 2 Runs Out. Let me explain: the regs tell us it is 2.5 meters from the bathtub. That’s how the regs word it, but the first 0.6 meters is zone 2, so the outside zones space is actually from 0.6 meters to 2.5 meters. This is the major change – this used to be up to three meters and a great exam question to catch you out.

All Zones Together

Look at both zones together now: 0.6 meters for zone 2 and then up to 2.5 meters for the outside Zone space. And this is all the zones together. If your bathroom is big enough and it exceeds the dimensions we’ve talked about and it extends into the green area on this drawing, then the normal rules and wiring regulations apply in the green area as we shall see.

Electrical Equipment in Zones

Moving on, what electrical equipment can we install in the zones? What IP ratings, what voltages, and so on?

Zone 0

Starting with Zone 0 inside the bathtub:

• Only IPX7 equipment is permitted
• Voltages are limited to a maximum of 12 volts AC and 30 volts DC (just a quarter of the normal extra low voltage limits)

Zone 1

Equipment here:

• Must be IPX4
• Maximum voltages of 25 volts AC or 60 volts DC (just half the ELV limits)
• Some permanently connected equipment is permitted in zone one, for instance: electric showers and shower pumps, Whirlpool units, fans and ventilation equipment, towel rails, water heaters, and Luminaires (but they must all be correctly IP rated)

Zone 2

Equipment must be:

• IPX4 rated
• If a shaver unit is installed, we must consider if direct jets of water are likely to fall on it from the shower
• Shaver sockets must be to BS EN6158-2-5 or equivalent
• Permanently connected equipment is permitted if it is correctly IP-rated
• SELV equipment is permitted back to the normal ELV limits now, but 230-volt switches or sockets are not permitted

Outside the Zones

In this outside zones space:

• Most of the general requirements of the regulations apply
• Accessories such as fuse spurs, switched FCUs, etc. are permitted but not 230 volt sockets

Beyond 2.5 Meters

Beyond 2.5 meters from the edge of the bathtub or more than 2.25 meters in height:

• We are into the green zone 
• Many bathrooms will just exceed 2.25 meters in height (great for mounting ceiling pull switches) but most bathrooms will not have floor spaces greater than 2.5 meters from the bath
• Occasionally you will come across them, but most times the bathroom is one of the smaller rooms in a house
• Now the general requirements apply to any equipment or wiring in the Green Space
• Accessories are allowed (fused spurs, etc.)
• 230 volt sockets are permitted but they must have 30 milliamp RCD protection

Additional Considerations

Underfloor and Wall Heating

Underfloor Heating and Wall heating installations (except SELV installations) must be covered by an earth metallic grid and the actual heating cables themselves must be in unearthed metallic sheath. This is a bathroom where people take their clothes off and stand on a wet floor – the regulations are there to make them safe.

Circuit Protection

• All circuits in a bathroom location must have 30 milliamp RCD protection except SELV circuits.
• Any circuit passing through Zone 1 or Zone 2 must have 30 milliamp RCD protection except SELV circuits, even if those cables and circuits are not supplying equipment in the zones.
• If it passes through the Zone then RCDs are needed.

SELV Equipment

• Most SELV equipment will be supplied by a 230-volt transformer (what we call the source)
• That Source (the 230-volt transformer) and the 230-volt cables must be physically situated outside the zones
• They can be in the Loft behind a wall, but they must be outside the zones (again, we’re protecting the users from electric shock)

Reference Information

Depending on which books you may have to hand, here is where to find relevant information and more in each of these books. I always have all three books with me as they each contain extra little bits of information that don’t appear in the others.

We are working on Amendment Two, the brown book. If you are still using the blue book or Amendment one then the page numbers and some of the information will not match.