What size circuit do I need for a hot tub?

Most domestic hot tubs in the UK draw between 5kW and 9kW. A smaller hot tub (up to 7kW, approximately 30A at 230V) requires a 32A dedicated circuit with 6.0mm² cable. Larger hot tubs (up to 9kW, approximately 39A at 230V) require a 40A circuit with 10.0mm² cable. Always check the manufacturer data plate for the exact current rating — do not guess from the kW rating alone, as the power factor and starting current of the pump motors can affect the required circuit rating. The circuit must be a dedicated radial circuit from the consumer unit — it must not be shared with any other load.

Do I need an RCD for a hot tub?

Yes. For a fixed hardwired hot tub, RCD protection is required under BS 7671 Section 702 (swimming pools and similar locations, applied to outdoor hot tubs), which is satisfied by an RCD with the characteristics of Reg 415.1.1 — a 30mA rated residual operating current. Reg 411.3.3 separately requires 30mA RCD protection for socket-outlets up to 32A and outdoor mobile equipment up to 32A (Reg 411.3.3(c)). A 30mA RCD or RCBO must protect the circuit. Type A is preferred over Type AC as hot tub pump motors and electronic control boards can produce pulsating DC fault currents that a Type AC RCD may not detect. For installations with variable-speed drives or inverter-controlled pumps (common in swim spas), a Type B RCD should be considered — Type B detects pulsating rectified DC from two or more phases as well as smooth DC residual currents. If the consumer unit already has RCD protection on the relevant way, verify it is 30mA and test it before relying on it.

How far can the hot tub be from the consumer unit?

There is no fixed maximum distance, but the cable run length affects voltage drop and earth fault loop impedance. BS 7671 limits voltage drop to 5% for the total installation (3% for the final circuit is the practical target). For a 40A circuit using 10.0mm² cable, the maximum run before exceeding 3% voltage drop is approximately 40 metres. For longer runs, increase the cable size to 16.0mm². Use the Elec-Mate cable sizing calculator to verify the voltage drop and Zs for your specific cable run length and installation method.

What IP rating does the outdoor isolator need?

A common specification for an outdoor hot tub isolator is IP56 (protected against powerful water jets and dust ingress), and many electricians fit IP66 for extra protection against heavy rain and pressure washing — both comfortably exceed the IPX4/IPX5 water-ingress minimum that BS 7671 Reg 702.512.2 sets for the zones around the tub. Use a lockable rotary type so the supply can be locked off during maintenance. Under Reg 702.53, switchgear must not be installed in zones 0 or 1, so the isolator must be positioned beyond the 2 metre zone 1 boundary around the rim — ideally still within sight of the tub for safe isolation.

Can I use a plug-in hot tub on a 13A socket?

Some small inflatable hot tubs (typically under 2kW) are sold with a 13A plug and are designed to be connected to a standard socket outlet. While these are legally sold, they are at the limit of a 13A circuit and must only be connected to a dedicated socket — not a shared ring final circuit with other high-load appliances. An RCD socket or plug-in RCD should be used. For any hardwired hot tub (which is the majority of acrylic/fibreglass models), a dedicated circuit with a fixed connection is required. Never connect a hardwired hot tub via a plug and socket.

Does hot tub wiring need to be notified under Part P?

Yes. Hot tub electrical work is notifiable under Part P of the Building Regulations: it is a new circuit, and the area around the tub is a special location under BS 7671 Section 702 (which the standard applies to outdoor hot tubs). The work must be either carried out by a registered competent person scheme member (NICEIC, NAPIT, etc.) who can self-certify, or notified to Building Control before the work starts. Failure to notify breaches the Building Regulations and can cause problems when selling the property.

What cable type should I use for an outdoor hot tub?

For the outdoor section of the cable run, SWA (Steel Wire Armoured) cable is the standard choice. SWA provides mechanical protection against accidental damage, rodent attack, and can be direct-buried (with warning tape above) or run on cable tray. The SWA armour also provides a CPC (Circuit Protective Conductor), though a separate earth core within the cable is still required. For the indoor section (consumer unit to the point of exit from the building), standard twin-and-earth or singles in conduit can be used. At the transition from indoor to outdoor, use an appropriate gland and adaptable box.

How much does it cost to get a hot tub wired in?

A typical hot tub electrical installation in the UK costs between £450 and £950 depending on the cable run length, cable size, and complexity. A straightforward installation with a 10-metre cable run, 32A circuit, SWA cable, isolator, and RCBO typically costs £450 to £600. Longer runs (20 to 30 metres), larger cable sizes (40A circuit), or installations requiring trenching, ducting, or consumer unit upgrades will be at the higher end. The cost includes materials (cable, isolator, RCBO, glands, clips), labour (typically half a day to a full day), testing, and the EIC certificate.

INSTALLATION GUIDE

Hot Tub Electrical Connection: Dedicated Circuit Guide for UK Electricians

Hot tubs need a dedicated 32A or 40A circuit with RCD protection, SWA cable, and a lockable outdoor isolator. This guide covers everything from supply assessment to testing and certification.

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12 min readUpdated 2026-06-10Andrew Moore, Founder of Elec-Mate

Written and reviewed by Andrew Moore, founder of Elec-Mate, against BS 7671:2018+A4:2026, IET Guidance Note 3 and the IET On-Site Guide.

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How do you connect a hot tub to the electrics in the UK?

A hot tub needs its own dedicated radial circuit from the consumer unit — normally 32A (6mm² cable) for tubs up to about 7kW or 40A (10mm²) up to about 9kW — protected by a 30mA RCD or RCBO. SWA cable feeds a lockable, IP-rated outdoor isolator sited outside the 2m zone around the tub. Supplementary bonding, full testing and an EIC are required, and the work is notifiable under Part P.

BS 7671 Section 702 applies its requirements to hot tubs installed outdoors, including supplementary equipotential bonding of metalwork in zones 0, 1 and 2 (Reg 702.415.2) and the prohibition on switchgear inside zones 0 and 1 (Reg 702.53).

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Key Takeaways

1Hot tubs require a dedicated radial circuit — typically 32A for smaller tubs (up to 7kW) or 40A for larger models (up to 9kW). Never connect a hot tub to an existing socket circuit.
2RCD protection is mandatory — a 30mA RCD or RCBO must protect the hot tub circuit. BS 7671 Section 702 calls for additional protection in this special location using an RCD with the characteristics of Reg 415.1.1 (30mA), and Reg 411.3.3 separately requires 30mA RCD protection for socket-outlets and outdoor mobile equipment up to 32A.
3Supplementary equipotential bonding is required under BS 7671 Reg 702.415.2 — all extraneous-conductive-parts in zones 0, 1 and 2 (tub metalwork, pipework, pump housing, handrails) must be connected by supplementary protective bonding conductors to the protective conductors of exposed-conductive-parts of equipment in those zones.
4All outdoor electrical equipment must have an appropriate IP rating — IP56 minimum for the isolator switch, and the cable route must be protected against mechanical damage using SWA cable or conduit.
5Switchgear and socket-outlets must not be installed in zones 0 or 1 (BS 7671 Reg 702.53). Because zone 1 extends to a vertical plane 2 metres from the rim of the tub, the lockable IP-rated isolator must sit beyond that 2 metre zone — and, as good isolation practice, within sight of the tub.
6An Electrical Installation Certificate (EIC) must be issued for the new circuit, and the work must be notified under Part P of the Building Regulations as it involves a special location (zone around a hot tub).

01 · Installation Guide

Hot Tub Electrical Connection: What Every Electrician Needs to Know

Hot tub installations are one of the most common domestic outdoor electrical jobs in the UK. The work is straightforward for a qualified electrician, but the combination of water, outdoor exposure, and high current draw means the installation must be done correctly. Cutting corners on hot tub wiring is genuinely dangerous.

Most hardwired hot tubs draw between 5kW and 9kW — that is 22A to 39A at 230V. They need a dedicated radial circuit from the consumer unit with appropriate cable sizing, RCD protection compliant with BS 7671:2018+A4:2026, and a lockable isolator within sight of the tub. The installation must be notified under Part P of the Building Regulations as it involves a special location.

This guide covers supply requirements, RCD protection, cable selection, IP ratings for outdoor equipment, step-by-step installation, testing, certification, and realistic pricing for 2026.

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02 · Installation Guide

Supply Requirements: 32A or 40A Dedicated Circuit

The first step is to check the hot tub manufacturer data plate for the rated current. This determines the circuit rating and cable size:

32A Circuit (up to 7kW)

Suitable for smaller hot tubs drawing up to 30A. Use 6.0mm² SWA cable for runs up to approximately 30 metres. Protected by a 32A Type C MCB or RCBO at the consumer unit. This covers most 4 to 6 person hot tubs with a single pump and heater.

40A Circuit (up to 9kW)

Required for larger hot tubs with multiple pumps, blowers, and higher-rated heaters drawing up to 39A. Use 10.0mm² SWA cable. Protected by a 40A Type C MCB or RCBO. This covers premium 6 to 8 person hot tubs and swim spas. Always verify against the manufacturer data — some large swim spas require a 50A or even a three-phase supply.

Rated load

Approx. current (230V)

Protective device

Typical SWA size

Up to 5kW

~22A

32A MCB / RCBO

6.0mm²

Up to 7kW

~30A

32A MCB / RCBO

6.0mm²

Up to 9kW

~39A

40A MCB / RCBO

10.0mm²

Over 9kW / swim spa

40A+ (or 3-phase)

50A device or split supply

16.0mm²+ / per design

Indicative only — always size the device and cable from the manufacturer data plate current and the installation method, not from the kW figure alone.

Before starting, verify the existing supply has sufficient spare capacity. Check the main fuse or service head rating (typically 60A or 100A for domestic properties) and calculate the maximum demand with the hot tub included. If the addition of a 32A or 40A circuit would exceed the available capacity, the DNO may need to upgrade the service head.

03 · Installation Guide

RCD Protection: BS 7671 Section 702 and Reg 415.1.1

RCD protection is mandatory for hot tub circuits. For a fixed hardwired hot tub, the governing requirement is BS 7671 Section 702 (swimming pools and similar locations, applied to outdoor hot tubs), whose additional-protection provisions are met using an RCD with the characteristics specified in Reg 415.1.1 — that is, a rated residual operating current not exceeding 30mA. Separately, Reg 411.3.3 requires 30mA RCD additional protection for socket-outlets up to 32A and for outdoor mobile equipment up to 32A (Reg 411.3.3(c)). In every case, a 30mA RCD or RCBO must protect the circuit.

30mA RCD or RCBO — the circuit must be protected by a 30mA device at the consumer unit. An RCBO (combined MCB and RCD) on the dedicated way is the cleanest solution — it provides both overcurrent and earth fault protection without affecting other circuits if it trips.
Type A RCD — preferred over Type AC for hot tub circuits. Hot tub pump motors and electronic control boards can produce pulsating DC fault currents that a Type AC RCD may not detect. Type A RCDs detect both AC and pulsating DC residual currents.
Type B RCD for inverter-driven installations — swim spas and premium hot tubs with variable-speed drives or multi-pump inverter controllers can produce pulsating rectified DC from two or more phases. A Type A RCD will not detect smooth DC fault currents. Where such equipment is installed, a Type B RCD should be specified — it covers all Type A fault current waveforms plus smooth DC and pulsating rectified DC from multi-phase rectification. Check the manufacturer's installation manual for the required RCD type.
Nuisance tripping — hot tub motors and heaters can cause nuisance tripping on sensitive RCDs, particularly at start-up. Ensure the RCD is rated for the inductive load and consider a slight time delay (Type S RCD) only on a secondary upstream device — the 30mA device protecting the circuit must always be instantaneous.

04 · Installation Guide

Cable Selection and Routing

The cable route from the consumer unit to the hot tub typically involves an indoor section (within the building) and an outdoor section (to the hot tub location). The outdoor section must use a cable type that withstands weather, UV exposure, and mechanical damage.

SWA cable (Steel Wire Armoured) — the standard choice for the outdoor section. 3-core SWA (line, neutral, earth) in 6.0mm² (32A circuit) or 10.0mm² (40A circuit). BS 7671 Reg 522.8.10 requires a cable buried in the ground to have earthed armour or metal sheath and to be at a sufficient depth — in practice electricians bury garden runs around 450–600mm with marker tape above, or surface-mount on cable cleats. The steel wire armour provides mechanical protection and acts as an additional CPC.
Indoor section — from the consumer unit to the point of exit from the building, 6242Y (twin-and-earth) or singles in conduit/trunking are acceptable. Transition from indoor to outdoor requires an IP-rated junction box or adaptable box with SWA glands.
Voltage drop — check the voltage drop for the total cable run. BS 7671 allows 5% total; aim for 3% on the final circuit. For a 40A load on 10.0mm² cable, the maximum run for 3% voltage drop is approximately 40 metres. Use the cable sizing calculator to verify.

05 · Installation Guide

Outdoor IP Ratings

All electrical equipment installed outdoors for a hot tub must have an appropriate Ingress Protection (IP) rating. The IP rating indicates protection against solid objects (first digit) and water (second digit). BS 7671 Reg 702.512.2 sets the minimum protection by zone; the practical specifications below meet or exceed those minimums for typical weather-exposed outdoor equipment.

Zone

BS 7671 minimum (Reg 702.512.2)

Extent

Zone 0

IPX8

Interior of the basin / tub

Zone 1

IPX4 (IPX5 where water jets used for cleaning)

Within 2m of the rim, up to 2.5m high

Zone 2 (outdoor)

IPX4 (IPX5 where water jets used for cleaning)

A further 1.5m beyond zone 1

The second digit (water) is what 702.512.2 fixes by zone; specify the first digit (dust / solid ingress) to suit the location — full IP ratings such as IP56 or IP66 comfortably satisfy these minimums.

Isolator Switch

IP56 is a common spec, IP66 for heavy exposure. Lockable rotary type. Reg 702.53 bars switchgear from zones 0 and 1, so site it beyond the 2m zone — ideally within sight of the tub.

Junction Boxes

IP65 minimum for any outdoor junction or adaptable box. Use boxes with cable glands rather than knockouts for a reliable seal.

Cable Glands

SWA glands at both ends of the armoured cable must be correctly installed with inner and outer gland nuts, earth tags, and shrouds to maintain the IP rating of the enclosure.

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06 · Installation Guide

Step-by-Step Installation

A typical hot tub electrical installation follows these steps:

Survey and assessment — check the manufacturer data plate, determine circuit rating (32A or 40A), survey the cable route, verify spare capacity at the consumer unit, and check the earthing arrangement (TN-S, TN-C-S, or TT).
Install the RCBO or MCB — fit an appropriately rated RCBO (or MCB behind an RCD) in the consumer unit on a dedicated way. Label clearly as "Hot Tub".
Run the cable — route twin-and-earth or singles in conduit from the consumer unit to the building exit point. Transition to SWA cable using an IP-rated adaptable box with SWA glands. Route the SWA to the isolator position — either buried in a trench at a sufficient depth (commonly 450–600mm) with marker tape above (Reg 522.8.10) or surface-mounted on cleats.
Install the isolator — mount a lockable IP56/IP66 rotary isolator beyond the 2 metre zone 1 boundary around the rim (Reg 702.53 bars switchgear from zones 0 and 1). Gland the SWA into the isolator. Run a short length of SWA or flexible armoured cable from the isolator to the hot tub connection point.
Make the final connection — connect to the hot tub terminal block as per the manufacturer instructions. Verify the connection is within an IP-rated enclosure.
Test — complete all initial verification tests (continuity, insulation resistance, polarity, earth fault loop impedance, RCD operation). Fill and power the hot tub. Check for correct operation of pumps, heater, lights, and controls.
Certify — issue an Electrical Installation Certificate (EIC) and notify under Part P.

07 · Installation Guide

Testing and Certification

The completed hot tub circuit must be tested in accordance with BS 7671 Chapter 64. The following tests are required:

Continuity of protective conductors — CPC from consumer unit to isolator and from isolator to hot tub earth terminal
Test in the order set out in BS 7671 Reg 643.1 — the dead tests (continuity, insulation resistance, polarity) before energising, then the live tests (Zs, RCD operation). A hot tub is a dedicated radial, so ring-continuity testing does not apply.
Insulation resistance — 500V DC between live conductors and earth, minimum 1 megohm (disconnect the hot tub before testing)
Polarity — verify correct line, neutral, and earth connections at all points
Earth fault loop impedance (Zs) — must be within the maximum permitted Zs for the protective device. When comparing the measured Zs against the tabulated maximum, apply the IET Guidance Note 3 rule-of-thumb correction factor of 0.8: a measured Zs is acceptable if it does not exceed 0.8 × the tabulated maximum Zs, allowing for the rise in conductor resistance at operating temperature. Record both the measured and corrected values on the EIC schedule.
RCD operation — 30mA device must trip within 300ms at rated current, and within 40ms at 5x rated current

Supplementary Equipotential Bonding — Reg 702.415.2

All extraneous-conductive-parts within zones 0, 1 and 2 must be connected by supplementary protective bonding conductors. This includes the metalwork of the tub shell, water inlet and outlet pipework, pump housing, handrails, and any other metalwork within or bounding the zones. The bonding conductors connect these parts to the protective conductors of exposed-conductive-parts of equipment in the zones. Omitting this bonding is a mandatory non-compliance under BS 7671 Reg 702.415.2 and is among the most common dangerous mistakes on hot tub and pool installations. Verify continuity of each bonding conductor and record on the EIC.

An Electrical Installation Certificate (EIC) must be issued. A Minor Works Certificate is not appropriate because the work involves a new circuit in a special location. The EIC should reference BS 7671 Section 702 in the remarks.

08 · Installation Guide

Realistic Pricing for Hot Tub Electrical Installation (2026)

Pricing varies by cable run length, cable size, and local labour rates. The following are realistic prices for 2026 in the UK:

Scenario

Indicative price

What it covers

Short run (under 10m), 32A

£450–£600

RCBO, 6.0mm² SWA, IP66 isolator, glands, testing, EIC

Medium run (10–20m), 32A

£550–£750

Longer cable run, possible trenching

Long run (20–30m), 40A

£700–£950

10.0mm² SWA, more labour for trenching and backfill

Consumer unit upgrade

+£350–£600

If no spare ways or the board needs replacing

Customer digs trench

−£100–£200

Deduct from the figures above

Indicative UK market guidance for 2026, not a quote — actual pricing depends on the cable route, local labour rates and site access.

These prices include materials, labour, testing, and the EIC certificate. They do not include the hot tub itself, the base/pad, or any plumbing work. Labour is typically half a day for a straightforward installation, or a full day for longer runs with trenching.

09 · Installation Guide

For Electricians: Hot Tub Installation Tips

Hot tub installations are profitable, repeatable work. A typical job takes half a day to a full day and is worth £450 to £950. Here are practical tips from experienced installers:

Always Get the Data Plate First

Before quoting, ask the customer for the hot tub make, model, and data plate photo. The rated current determines the circuit size. Quoting a 32A circuit for a hot tub that needs 40A means returning to upgrade — at your cost.

Quote Accurately with Elec-Mate

Use the quoting app to itemise materials (SWA cable per metre, RCBO, isolator, glands, clips, warning tape) and labour. Send a professional PDF quote from the survey.

Certify on Site

Complete the EIC on your phone before you leave using the EIC certificate app. Note the BS 7671 Section 702 reference in the remarks. Send the PDF to the customer immediately — it is professional and avoids the paperwork backlog.

Quote, install, and certify hot tub connections

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Frequently Asked Questions About Hot Tub Electrical Connections

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Hot Tub Electrical Connection: Dedicated Circuit Guide for UK Electricians

How do you connect a hot tub to the electrics in the UK?

Key Takeaways

Hot Tub Electrical Connection: What Every Electrician Needs to Know

Get the BS 7671 A4:2026 Cheat Sheet — free

Supply Requirements: 32A or 40A Dedicated Circuit

32A Circuit (up to 7kW)

40A Circuit (up to 9kW)

RCD Protection: BS 7671 Section 702 and Reg 415.1.1

Cable Selection and Routing

Outdoor IP Ratings

Isolator Switch

Junction Boxes

Cable Glands

Try Elec-Mate free for 7 days

Step-by-Step Installation

Testing and Certification

Realistic Pricing for Hot Tub Electrical Installation (2026)

For Electricians: Hot Tub Installation Tips

Always Get the Data Plate First

Quote Accurately with Elec-Mate

Certify on Site

Quote, install, and certify hot tub connections

Frequently Asked Questions About Hot Tub Electrical Connections

What size circuit do I need for a hot tub?

Do I need an RCD for a hot tub?

How far can the hot tub be from the consumer unit?

What IP rating does the outdoor isolator need?

Can I use a plug-in hot tub on a 13A socket?

Does hot tub wiring need to be notified under Part P?

What cable type should I use for an outdoor hot tub?

How much does it cost to get a hot tub wired in?

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