How to Look After Your Swim Spa Through a UK Winter

A swim spa is one of the few ways to swim outdoors at home all year round, and plenty of our owners use theirs more in winter than in summer. It holds far more water than a hot tub, though, so winter takes a little more planning. Here's how to keep yours safe from frost and as cheap to run as possible while you keep swimming.

Keep it powered and full

The single most important winter rule is to leave the swim spa switched on. Our St Lawrence swim spas have built-in freeze protection. If the sensors detect the temperature in the heater dropping to about 6.7°C, the pumps start automatically and keep the water moving until it is back above about 7.2°C. That only works while the spa has power and enough water in it.

• Don't switch off at the isolator to save electricity. A full swim spa with no power has no frost protection at all.
• Keep the water at the correct level. Cold, dry air increases evaporation, and a low level can let the pumps draw in air.

Pick the right heat mode and filter cycles

The topside panel offers three modes. Our St Lawrence operating guide shows the button presses for each one.

• Standard keeps the water at your set temperature all the time. It suits a spa you use most days.
• Economy heats to the set temperature, but only during filter cycles.
• Sleep heats to within about 10°C of the set temperature, again only during filter cycles.

Filter cycles run twice a day, 12 hours apart, timed from when the spa was first powered up. Each cycle can be set from 1 to 12 hours, and two cycles a day is the recommended setting. If you swim most days, Standard is usually the better choice, because reheating thousands of litres from cold takes a lot of energy and time.

Keep the heat in

Most heat escapes through the surface of the water, so the cover does most of the work in winter. To put that in numbers, the St Lawrence 16 holds about 6,475 litres, and raising that by just 1°C takes about 7.5 kWh of heat. Every degree the cover holds on to overnight is money you keep.

• Close the cover as soon as you get out and fasten the locking straps every time.
• Brush off leaves before you open it, and clear heavy snow so the weight doesn't stress the cover.
• Check for gaps, a sagging middle or a heavy, waterlogged feel. A cover that has absorbed water insulates far less well.

If lifting a long, heavy cover is putting you off using the spa on dark evenings, a rolling cover is worth a look. One person can open it in under a minute, and its domed top lets rain and snow run off. Our guide to rolling swim spa covers lists the sizes and prices.

Consider a heat pump

On a swim spa, heating is most of the running cost, so a heat pump can make a real difference. The Balboa Clim8zone II Heat Pump is the larger model designed for swim spas. Balboa quotes 5 to 10 times the efficiency of a traditional spa heater, a 6 kW heating capacity and operation in air temperatures down to -20°C. It works less efficiently on a freezing night, so the cover still matters. Our heat pump guide explains how the savings work and whether one makes sense for you.

Water care in the cold

• Test two to three times a week and keep the sanitiser and pH in range. Chlorine keeps things simple for most owners.
• Rinse the filters regularly. Replace swim spa filters every 6 to 12 months depending on use. Our 200 sq ft Swim Spa Filter Set (£180) fits St Lawrence swim spas bought after 2011.
• Most owners change the water every four to six months. If yours is due, do it in late autumn, before the hard frosts arrive, rather than draining in sub-zero weather. Our guide to draining and refilling covers the signs it's time, and the same rules apply to a swim spa.
• If the pH keeps drifting up and down even though you're dosing correctly, too much detergent has built up in the water, and a fresh fill is the answer.

Swimming safely on winter evenings

The NHS recommends adults do at least 150 minutes of moderate activity a week, and its physical activity guidelines include swimming. A swim spa may help you keep that going when the days are short. A few habits keep winter sessions safe and comfortable:

• Light the path and keep steps clear of leaves, frost and ice.
• If you have a health condition, speak to your GP before starting a new exercise routine.
• You should not use the warm spa end of a swim spa, or a hot tub, while pregnant.
• Always supervise children, and lock the cover straps when the spa isn't in use.

If you won't use it this winter

If the swim spa will sit unused for months, or the property will be without power, it needs a full winterise rather than simply being switched off. Every drop of water has to come out of the pipework, pumps and heater, or freezing water can crack them. Our Swim Spa Winterising service (£350) flushes and drains the system, disconnects the pipework from the pumps and heater, cleans the spa and cover, and shrink-wraps the surface. The spa then stays off and empty until you're ready to start again.

Common questions

What happens if there's a power cut in a frost?

Keep the cover closed and fastened to hold in as much heat as possible. Once the power is back, check the pumps are running and the display is normal. If the power is off for a long time in very cold weather, call us for advice before you drain anything.

Can I keep the swim end cooler than the spa end?

On the 20ft St Lawrence dual temperature model, yes. Each side has its own heater and controls, so you can run the swim end cooler for exercise and keep the spa end warm for a soak afterwards. On single-zone models the whole spa shares one temperature.

If you'd like advice on running your swim spa this winter, or you want to book a service, call Canadian Spa Company on 01293 824094 and we'll talk it through with you.