Section 701 of BS 7671 divides a room containing a bath or shower into three zones: zone 0 inside the bath or shower tray, zone 1 above it to 2.25 m from the floor, and zone 2 extending 0.6 m horizontally beyond zone 1. Zone 0 needs IPX7 and SELV at 12 V a.c. maximum; zones 1 and 2 need IPX4. Whatever the zone, Regulation 701.411.3.3 requires every circuit serving the location to have 30 mA RCD additional protection, and Regulation 701.415.2 requires supplementary bonding unless three specific conditions are met. Amendment 4:2026, published 15 April 2026, leaves Section 701 unchanged, so these rules carry straight through when A2 is withdrawn on 15 October 2026.
- Zones: 0 inside the bath or tray; 1 above it to 2.25 m (or a 1.2 m radius from a shower head with no tray); 2 a further 0.6 m outwards. The 16th Edition's zone 3 was dropped in 2008.
- IP ratings: IPX7 in zone 0, IPX4 in zones 1 and 2 (IPX5 if water jets are used for cleaning). No minimum from Section 701 outside the zones.
- Every circuit serving the bathroom needs a 30 mA RCD, including a lighting circuit shared with other rooms and any circuit merely passing through zones 1 and 2.
- Supplementary bonding can be omitted only when all circuits meet disconnection times, all have 30 mA RCD protection, and all extraneous-conductive-parts are main-bonded. Test, do not assume.
- No socket-outlets within 3 m horizontally of zone 1 except SELV sockets and shaver supply units to BS EN 61558-2-5 in zone 2.
- Additions and alterations inside the zones are notifiable under Part P in England; a new shower circuit is notifiable anywhere.
What are the bathroom zones and how are they measured?
A location containing a bath or shower is a special location because water and a wet, unclothed person lower body resistance and raise the chance that a shock is fatal. Section 701 applies to any room with a fixed bath or shower, including en-suites, wet rooms and a shower cubicle standing in a bedroom. It does not apply to a room with only a basin or a WC, and it does not apply to emergency showers in industrial premises or laboratories, which Regulation 701.1 excludes.
| Zone | Extent | Notes |
|---|---|---|
| Zone 0 | The interior of the bath tub or shower basin | For a shower without a basin, the area on the floor within 1.2 m of the fixed water outlet, to a height of 0.1 m |
| Zone 1 | Above zone 0, bounded by the vertical planes around the bath or basin, from the floor to 2.25 m or to a higher fixed shower head or water outlet | Includes the space under the bath if it is accessible without a tool. For a shower without a basin, a 1.2 m radius around the fixed water outlet |
| Zone 2 | The area 0.6 m horizontally beyond the boundary of zone 1, to a height of 2.25 m | For a shower without a basin there is no zone 2; zone 1 is enlarged to 1.2 m instead |
| Outside the zones | The rest of the room | Still within the location: the RCD, bonding and socket-outlet rules apply everywhere in the room |
Zones are measured taking account of fixed partitions with a permanent barrier effect. A fixed, floor-to-ceiling shower screen bounds zone 1; a hinged or folding bath screen does not, because it can be opened. Regulation 701.30.2 says the zones are determined with any door or partition taken into account, so a shower cubicle with a proper door has its zone 1 inside the door and the rest of the room is outside the zones. The space under a bath is zone 1 when the panel clips off by hand and outside the zones when it is screwed on, which matters for shower pumps and whirlpool motors.
For a wet room with a walk-in shower and no tray, the 1.2 m radius from the fixed water outlet defines zone 1 and there is no zone 2 at all. Where the water outlet is a ceiling-mounted head, the radius is measured from that head at its height and downwards. Above 2.25 m in an ordinary bathroom, the ceiling space is outside the zones, though a luminaire there still sits in a wet, steamy location and Regulation 512.2 still asks whether it is suitable for the external influences.
What IP rating and equipment is allowed in each zone?
An IP rating to BS EN 60529 is a two-digit code. Section 701 only specifies the second digit, protection against water, so the first digit appears as an X. IPX4 means protected against splashing from any direction; IPX5 against jets from a nozzle; IPX7 against temporary immersion at up to 1 m depth for 30 minutes. A fitting marked IP44 or IP65 meets the zone 1 and 2 requirement; a fitting with no IP marking does not, whatever it looks like. The rating applies to the face exposed to the location, so a recessed downlight rated IP44 from below is acceptable in zone 1 even though its back is IP20 in the ceiling void.
| Zone | Minimum IP rating | Permitted current-using equipment | Switches and accessories |
|---|---|---|---|
| 0 | IPX7 | Only fixed SELV equipment at no more than 12 V a.c. or 30 V d.c., designed for the zone, with the source outside zones 0, 1 and 2 | None |
| 1 | IPX4 (IPX5 if water jets used for cleaning) | Fixed, permanently connected equipment listed in 701.55: whirlpool units, electric showers, shower pumps, ventilation, towel rails, water heaters, luminaires. SELV or PELV at 25 V a.c. or 60 V d.c. maximum | Switches of SELV circuits at 12 V a.c. or 30 V d.c. with the source outside the zones; the cord of a cord-operated switch |
| 2 | IPX4 (IPX5 if water jets used for cleaning) | Fixed equipment suitable for the zone: luminaires, fans, heaters, mirror lights | Shaver supply units to BS EN 61558-2-5; SELV switches and socket-outlets; the cord of a cord-operated switch |
| Outside zones | None from Section 701 | Anything suitable for the conditions | Ordinary switches permitted; socket-outlets only 3 m or more horizontally from zone 1 (701.512.3) |
Zone 0 in practice contains almost nothing: a SELV underwater bath light with its transformer well outside the zones, or the SELV sensors of a whirlpool bath. Any 230 V equipment in zone 0 is a C2 on an EICR without further discussion.
Where does each common bathroom item go?
The questions on site are rarely about the zone diagram; they are about a specific product. The table below is the usual placement for the items that turn up on most jobs, checked against 701.55 and 701.512.3.
| Item | Where it can go | What to check |
|---|---|---|
| Electric shower | Zone 1 as fixed equipment | IPX4 minimum; dedicated circuit; 30 mA RCD; double-pole switch for mechanical maintenance with only the cord inside the zones |
| Shower pump under the bath | Zone 1 if the panel is removable by hand; outside zones if screwed on | IPX4 in zone 1; fused connection unit outside the zones; pump must be suitable for the location |
| Extractor fan | Zone 1 or 2 as fixed equipment | IPX4; 230 V fan must be designed for the zone; SELV fan with transformer outside the zones is the common alternative; three-pole isolator outside the zones for a timer fan |
| Downlights | Zone 1 or 2 | IPX4 minimum; ceiling fittings above 2.25 m are outside the zones but should still suit the conditions |
| Heated towel rail | Zone 1 or 2 as fixed equipment | IPX4; fused connection unit outside the zones; Class I rails need a sound cpc and are exposed-conductive-parts for bonding purposes |
| Shaver supply unit | Zone 2 or outside the zones | Must be to BS EN 61558-2-5 with an isolating transformer; a plain 13 A socket in a mirror cabinet is not a shaver unit |
| Illuminated mirror or mirror cabinet | Zone 2 or outside the zones | IPX4 in zone 2; any integral socket must be a shaver supply unit if within 3 m of zone 1 |
| Electric underfloor heating | Under the floor anywhere in the location | Regulation 701.753: metal sheath, enclosure or fine-mesh earthed grid connected to the cpc; 30 mA RCD; check the manufacturer's data because many cheap mats are not suitable |
| Whirlpool or spa bath | Zone 1 | Listed in 701.55; follow the manufacturer's instructions; motor usually under the bath, so check the panel and the IP rating |
| 13 A socket-outlet | Only 3 m or more horizontally from zone 1 | Measured from the bath rim or tray edge; a socket in a small bathroom is almost always a defect |
| Light switch | Outside the zones, or a cord-operated switch with only the cord in zones 1 and 2 | Ordinary plate switches are not permitted in zones 0, 1 or 2 |
An 8.5 kW shower draws about 37 A at 230 V and a 10.5 kW shower about 46 A, so a new shower is a new circuit with its own cable calculation and an Electrical Installation Certificate rather than a Minor Works Certificate; Electric Shower Installation Certificate: EIC or Minor Works? covers which form to use and Cable Sizing and Volt Drop Basics: Ib, In, Iz and Table 4D5 covers the sums.
Why does every bathroom circuit need a 30 mA RCD?
Regulation 701.411.3.3 requires additional protection by an RCD with a rated residual operating current not exceeding 30 mA for all low-voltage circuits serving the location, and for circuits passing through zones 1 and 2 to supply equipment elsewhere. This is deliberately broader than Regulation 411.3.3, which covers socket-outlets and mobile equipment outdoors, and 411.3.4, which covers lighting in domestic premises. In a bathroom the risk does not depend on which accessory the person touches: the lighting circuit that also feeds the landing, the shower, the fan and the towel rail are all included, and so is a ring final circuit that happens to be routed through the wall of zone 2 on its way to the bedroom.
A 30 mA RCD is designed to disconnect within 40 ms at five times its rated residual current, which is the product standard figure in Regulation 415.1.1 and the reason the device is credited as additional protection rather than fault protection. BS 7671 Regulation 643.8 only requires a test at the rated residual current, with a maximum of 300 ms for a general type; RCD Testing Explained: Types, Test Currents and Trip Times sets out the sequence and what to record. The rule is not retrospective, but an unprotected bathroom is the first thing an EICR picks up, and the code depends on whether supplementary bonding is present. Split-load boards with one RCD covering the shower and the lighting are common in 2010-era installations; RCBO vs RCD Split-Load Boards: Which to Fit and Why explains why an RCBO per circuit is the better arrangement when the board is replaced.
When is supplementary bonding required and when can it be omitted?
Supplementary protective bonding connects the exposed-conductive-parts of fixed equipment in the location, such as the shower casing, a Class I luminaire or a metal towel rail, to the extraneous-conductive-parts, such as metal pipes and a metal bath in contact with pipework, so that during a fault they rise in potential together and the touch voltage stays low. It was mandatory in every bathroom until the 17th Edition in 2008 introduced the three-condition test that now sits in Regulation 701.415.2. Main protective bonding of the incoming services is a separate matter and is always required; see What is main protective bonding? Explained.
Regulation 701.415.2 allows supplementary bonding to be omitted only where all three of the following are met.
| Condition | What it means on site |
|---|---|
| All final circuits of the location meet the disconnection times of Regulation 411.3.2 | Zs of every circuit serving the room is within the limit for its device, verified by test against the tables in Maximum Zs Values BS 7671: Tables, 80% Rule and Ze |
| All final circuits of the location have 30 mA RCD additional protection | Every circuit, not just those in the zones, and the RCD must pass its test |
| All extraneous-conductive-parts of the location are effectively connected to the main protective bonding under Regulation 411.3.1.2 | The metal pipes entering the room are continuous back to the main-bonded incoming services, confirmed by measurement, not by looking |
If any condition is not met, supplementary bonding is required. The third condition is the one that catches people. All-plastic pipework has nothing to bond, but a house where copper has been partly replaced with push-fit may leave a towel rail's copper tails no longer continuous back to the bonded incoming water. Test between the pipe and the main earthing terminal with the installation isolated: IET Guidance Note 8 treats a result above about 22 kΩ as showing the part is not extraneous, and a low reading in the order of an ohm or less as effectively connected. Anything in between is a part that is earthy enough to matter but not bonded well enough to rely on, and it needs a bonding conductor.
Where supplementary bonding is installed, Regulation 544.2 sets the conductor size: 4 mm² copper if not mechanically protected, 2.5 mm² if it is, and it may run under the bath or behind the panel provided it is accessible for inspection where practicable. The bonding conductor need not go back to the consumer unit; connecting the parts together locally is the point. The verification test in Regulation 415.2.2 is that the resistance between simultaneously accessible exposed and extraneous parts does not exceed 50 divided by Ia: for a 32 A Type B breaker Ia is 160 A, so the limit is 0.31 Ω, and for a 6 A Type B lighting circuit it is 50/30, or 1.67 Ω.
How do you test and verify a bathroom installation?
A bathroom is inspected and tested like any other part of the installation, but the sequence puts extra weight on the three items that Section 701 relies on. On a new circuit the results go on the schedule of test results attached to the EIC; on an EICR the same tests decide whether the 701.415.2 conditions hold.
| Test | What to do | Pass criterion |
|---|---|---|
| Continuity of supplementary bonding | Low-resistance ohmmeter between each exposed-conductive-part and each extraneous-conductive-part | Not exceeding 50/Ia for the circuit concerned (415.2.2) |
| Extraneous-conductive-part check | Insulation tester or high-range ohmmeter from pipe to main earthing terminal, installation isolated | Above about 22 kΩ means not extraneous; a low reading means main bonding must be effective |
| Continuity of cpc to shower, fan, towel rail and Class I luminaires | R1+R2 method as in Continuity Testing: R1+R2 Method, Wander Lead and Values | Consistent with cable length and size; used to confirm Zs |
| Insulation resistance | 500 V d.c. between live conductors and earth with SELV transformers and electronic fan timers disconnected; see Insulation Resistance Testing Guide: Voltages, Minimums, Method | Not less than 1 MΩ; investigate anything under 2 MΩ |
| Earth fault loop impedance | Zs at the shower isolator, fan and luminaire | Within the corrected maximum for the device |
| RCD operation | At IΔn per 643.8; most electricians also record 5 IΔn | 300 ms maximum at IΔn for a general type; 40 ms at 5 IΔn is the product figure |
| Polarity | Confirm the shower switch and fan isolator break the line, and the permanent live at a timer fan is correctly identified | Correct at every point |
SELV circuits in the location are tested at 250 V d.c. between the SELV conductors and earth, and the separation from the 230 V side is verified by a 500 V test from the primary to the SELV output; SELV, PELV and FELV Explained: Extra-Low Voltage on Site explains the difference between SELV, PELV and FELV and why only SELV is allowed in zone 0.
Is bathroom work notifiable under Part P?
In England since April 2013 the notifiable work under Part P of the Building Regulations is a new circuit, a consumer unit replacement, and any addition or alteration to an existing circuit in a special location, which for a bathroom means the space around the bath or shower to 2.25 m high and 0.6 m out, corresponding to zones 0 to 2. A new shower circuit is notifiable anywhere; moving a light fitting in zone 1 is notifiable; adding a downlight in zone 2 is notifiable; replacing a switch outside the zones, or a like-for-like fan, is not. Wales retains the wider pre-2013 list, so an added fused connection unit anywhere in a Welsh bathroom is notifiable. Use a competent-person scheme or notify building control before starting; Part P notification: what to notify, how, and by when sets out the routes and the time limits, and Minor Works Certificate: When to Use It (and When Not To) covers which certificate goes with the smaller jobs.
What are the common bathroom observations on an EICR?
The codes below follow Electrical Safety First Best Practice Guide 4 and the reasoning in EICR Observation Codes Explained: C1, C2, C3 and FI. The bathroom items are among the most frequent entries on domestic reports; EICR Fails: The Ten Most Common C1 and C2 Observations puts them in context with the other usual suspects.
| Finding | Usual code | Notes |
|---|---|---|
| No 30 mA RCD protection to circuits serving the bathroom, supplementary bonding present and sound | C3 | The bonding provides protection against a touch voltage; recommend RCD protection |
| No 30 mA RCD protection and no supplementary bonding, or bonding absent where required | C2 | Neither protective measure in place |
| 230 V equipment of any kind in zone 0 | C2 | Only SELV at 12 V a.c. is permitted |
| 13 A socket-outlet within the zones or less than 3 m from zone 1 | C2 in most cases | Regulation 701.512.3; record the distance measured |
| Luminaire or fan in zone 1 or 2 with no IP rating or below IPX4 | C2 in zone 1; C2 or C3 in zone 2 | Judge the likelihood of water reaching live parts and say so in the observation |
| Class I luminaire or accessory with no cpc connection | C2 | Fault protection absent |
| Supplementary bonding conductor disconnected, or clamp on painted pipe | C2 where bonding is relied on; C3 where the 701.415.2 conditions are otherwise met | Test it; a clamp that reads high is a disconnected conductor |
| Plate switch inside zone 1 or 2 | C2 | Only SELV switches and cord-operated switches are permitted in the zones |
| Shaver socket that is a plain 13 A or 2-pin socket without an isolating transformer | C2 | Must be to BS EN 61558-2-5 |
| Underfloor heating with no earthed sheath or grid | C2 | Regulation 701.753 |
A C2 makes the report unsatisfactory and, for a rented property in England, starts the 28-day remedial clock under the Electrical Safety Standards in the Private Rented Sector (England) Regulations 2020; Landlord EICR Regulations in England: The Electrician's Guide covers the landlord's duties from the electrician's side. Word the item precisely: zone, item, IP rating found, circuit reference, regulation, code. "Extractor fan in zone 1 above shower, no IP marking, circuit 3, Reg 701.512.2, C2" tells the next electrician exactly what to fix, whereas "bathroom fan not IP rated" does not. How to Write EICR Observations That Stand Up has more examples of wording that stands up.
What about hot tubs, kitchens and other wet locations?
Section 701 is only for baths and showers. A hot tub or swimming pool, indoors or out, is Section 702 with its own zones and a 30 mA RCD requirement of its own, and the Amendment 4 guidance notes that an indoor hot tub is often better treated using the Section 701 zoning concept; Hot Tub and Swimming Pool Wiring: Section 702 Explained explains the differences. A kitchen has no zones and no special-location status in BS 7671, although the Part P definition in England still treats it as ordinary work, so the socket-spacing and RCD rules there come from Chapter 41 and good practice rather than Part 7; Kitchen Electrics Regulations UK: Sockets, Circuits, Part P covers it. Whichever room it is, the earthing arrangement of the supply decides whether the disconnection times behind 701.415.2 can be met at all, and a TT system with a high Ze needs the RCD to do the fault-protection job too; Earthing Arrangements Explained: TN-S, TN-C-S and TT has the detail.
How Certio helps
Certio produces the EICR, EIC, Minor Works certificate and PAT records on the BS 7671 model forms and turns them into branded PDFs. Photograph the consumer unit and the circuit schedule drafts itself; point the phone camera at a Megger MFT-X1 and the reading goes straight into the schedule of test results, or dictate it while your hands stay on the probes. Suggested observation wording with the regulation reference is there for you to check and confirm. The judgement stays yours; the typing goes. Starter is free for 7 days, then £4.99 a month.