Plug-in or hard-wired?
Hot tubs come in two kinds electrically. Plug-and-play tubs run from a standard 13 amp socket, which limits the heater to about 2 kW, so they take a day or more to come up to temperature and struggle to hold it in a Fylde winter. Everything larger needs a hard-wired supply, usually 32 amps, on its own circuit from the consumer unit (the fuse box). Swim spas and tubs with big heaters sometimes need more, and your supplier’s spec sheet will say.
Even a plug-in tub should not run from an extension lead or an indoor socket through the window. It needs a proper outdoor socket, weatherproof and RCD protected, which we fit for £145 including VAT. If you are buying a tub and not sure which type you have, send us the model and we will tell you.
What a hot tub supply involves
A hot tub supply is a dedicated circuit: nothing else shares it, so the tub cannot trip the kitchen and the kitchen cannot trip the tub. From the consumer unit we run steel wire armoured cable, SWA, which has a layer of steel wire under the sheath and can be buried or run along walls without extra protection. The cable size depends on the distance and the current, and getting it right is what stops the heater running slow on a long run.
The circuit has its own RCD protection. An RCD is the device that cuts the power within a fraction of a second if current leaks to earth, and for a tub full of water with people in it, that is not optional. Near the tub we fit a rotary isolator, a weatherproof switch that disconnects the whole supply, positioned where it is easy to reach but not from inside the water. From the isolator, the final connection goes into the tub’s control box.
Then we test every part of the circuit and record the results. You receive an Electrical Installation Certificate (EIC), and because a new outdoor circuit is notifiable work under Part P of the Building Regulations, we register it with building control through NICEIC. The compliance certificate arrives in the post. Tub manufacturers often ask for these before they honour a warranty claim on the electrics.
Before your tub arrives
A little planning saves money and a second visit. Decide where the tub will sit and get the base in first: a level concrete pad or a reinforced deck, since a filled tub weighs well over a tonne. Ask your supplier for the electrical spec sheet, which tells us the current it needs and where its control box is. Think about the cable route from the house: across a lawn it goes in a trench, across paving we lift and relay a line of slabs, and along a wall it clips neatly.
Tell us if you want anything else out there, such as a socket for a pump or a cover lifter, or lighting around the tub, because it is cheaper to run it all at once. And book us before the delivery date, not after. A tub delivered with no supply ready is a tub you look at for a fortnight.
What it costs
A supply up to 32 amps with the rotary isolator, RCD protection, up to 15 metres of armoured cable, testing and certification is £520 including VAT. Longer cable runs, trenching across a large lawn, and tubs that need a bigger supply move the price up. If your consumer unit has no spare way, we fit a small additional board beside it. We give you a written price before we start.
Hot tubs on the Fylde coast
Hot tubs have become common in Blackpool’s holiday lets and in the gardens of the larger houses in Lytham and St Annes, and we have fitted a lot of them. In a holiday let the isolator needs to be clearly labelled and the supply robust enough for guests who will not read the manual. On the coast at Cleveleys and Fleetwood, the salt air gets into isolators and glands that are not properly sealed, so we use marine-grade enclosures on exposed walls and position the isolator out of the weather.
The commonest mistake we see is a tub running from a cable that is too small for the distance, often fitted by whoever delivered it. The heater runs slowly, the cable runs warm and sometimes the RCD trips when the pump and heater start together. If you have inherited a tub supply with the house and nobody can show you a certificate for it, we will test it and tell you whether it is right.
