Hot tub keeps tripping the RCD: what to check

RCD or breaker: what is tripping?

Look at your consumer unit. An RCD (residual current device) is usually a wider switch with a test button, protecting a group of circuits. It trips when it senses current leaking to earth, which with a hot tub often means moisture or an insulation fault. A circuit breaker (MCB) protects one circuit and trips when too much current flows, which suggests overload or a short circuit.

Many hot tub pump plugs also have their own protective device built into the plug, with a test and reset button. If that trips but the consumer unit does not, the fault is likely in the tub, its cable or the outdoor socket.

Safe checks with the power off

If you find damage, water inside the socket or scorch marks, do not use the socket or the tub until a qualified electrician has checked them.

1. 1

   Switch off at the socket and unplug the tub with dry hands. If anything looks burnt or wet, switch off at the consumer unit first.

2. 2

   Look at the outdoor socket: is the cover closed, is there water inside or signs of scorching?

3. 3

   Look at the plug and cable for cuts, crushing or water in the plug.

4. 4

   Remove any extension lead or adaptor. Most makers say not to use them.

5. 5

   Check whether other heavy appliances share the circuit, such as a kettle, washing machine or heater.

6. 6

   Let a damp socket or plug dry fully before trying again.

Note:Never touch plugs, sockets or the pump with wet hands or while standing in water. Do not open the pump unit or any socket. Do not hold an RCD switch up or replace it with a higher rated device.

Damp and extension leads

The most common cause of an RCD trip on outdoor equipment is moisture. Rain, condensation and splashes can get into a socket, a plug or the join in an extension lead. Even a lead rated for outdoor use can let water in at the connection. This is one reason makers advise against extension leads.

A weatherproof outdoor socket, fitted at a sensible height away from splashes and with its cover kept closed when the plug is in, is the right supply. If your only option is a long lead, have a qualified electrician fit a proper socket near the tub.

Overload on the circuit

An inflatable tub's heater draws around 2 kW, close to the limit of a 13 A plug when the pump and blower run too. If the outdoor socket is on a circuit shared with other heavy loads, the breaker may trip when they all run together. Try running the tub with other appliances on that circuit switched off. If that stops the trips, ask an electrician whether a dedicated supply is needed.

When it is the tub

If the socket and plug are dry and undamaged, no extension lead is used and the trips continue, the fault is likely inside the pump: the heater element, a seal letting water in or the wiring. Some pumps also show an error code. Do not keep resetting it. Note when it trips, for example only when the heater starts, and contact the maker or seller. A replacement pump may be covered by the warranty.

You can test the outdoor socket with another simple appliance, such as a lamp, but only if the socket shows no damage and is dry. If the other appliance also trips it, the socket or circuit needs an electrician.

See Lay-Z-Spa models →

Preventing trips

Our 13 amp vs 32 amp guide explains how much power a tub draws and why the supply matters.

• Use a weatherproof outdoor socket with RCD protection, fitted by a qualified electrician.
• Keep the plug and cable off the ground and out of puddles.
• Keep the socket cover closed and the pump unit out of standing water.
• Avoid extension leads and adaptors unless the manual allows them.
• Test the plug's protective device before each use as the manual describes.

Frequently asked questions

Why does my hot tub trip the electrics when it rains? Water is likely getting into the socket, plug or a lead. Unplug, let it dry and have a weatherproof socket fitted if needed.

Can I use an outdoor extension lead for my hot tub? Most makers say not to. Follow the manual, and have a socket fitted near the tub instead.

Why does it trip only when the heater comes on? That can point to a heater fault or an overloaded circuit. Stop using it and contact the maker or an electrician.

Is it safe to keep resetting the RCD? No. Repeated trips mean a fault. Stop and get it checked by a qualified electrician.