Q: Does a hot tub need an RCD?

Yes — 30 mA RCD protection is mandatory for outdoor equipment (BS 7671 Reg 411.3.3). Use a Type A RCD so it detects the pulsating DC fault currents that electronic hot-tub controls can produce. An IP65 double-pole isolator must also be within sight of the tub.

Q: Can I use twin and earth cable for a hot tub?

Not for the outdoor or underground section. T&E is not suitable outdoors or buried — use SWA (steel wire armoured) for the run to the tub. T&E may only be used inside, in the dry, up to the point the cable leaves the building.

Q: How deep must a hot tub SWA cable be buried?

A buried SWA cable must be at least 500 mm deep (600 mm under drives or roads), laid on and covered with sand, with cable warning tape above it (BS 7671 Reg 522.8.10). Hot tub installations are also Part P notifiable.

Question 1

What size cable do I need for a hot tub?

Accepted Answer

Size the cable from the hot tub's power rating: design current = kW × 1000 ÷ 230 V, then apply burial, grouping and ambient correction factors. A typical 7.5 kW tub draws about 32 A and needs 6 mm² SWA for a buried run. The calculator applies the BS 7671 correction factors and gives the minimum size.

Question 2

Does a hot tub need an RCD?

Accepted Answer

Yes — 30 mA RCD protection is mandatory for outdoor equipment (BS 7671 Reg 411.3.3). Use a Type A RCD so it detects the pulsating DC fault currents that electronic hot-tub controls can produce. An IP65 double-pole isolator must also be within sight of the tub.

Question 3

Can I use twin and earth cable for a hot tub?

Accepted Answer

Not for the outdoor or underground section. T&E is not suitable outdoors or buried — use SWA (steel wire armoured) for the run to the tub. T&E may only be used inside, in the dry, up to the point the cable leaves the building.

Question 4

How deep must a hot tub SWA cable be buried?

Accepted Answer

A buried SWA cable must be at least 500 mm deep (600 mm under drives or roads), laid on and covered with sand, with cable warning tape above it (BS 7671 Reg 522.8.10). Hot tub installations are also Part P notifiable.

Hot Tub Cable Size Calculator