Should I winterise my hot tub or run it through the winter?

It depends entirely on which sort of tub you have. A well insulated hardshell spa with a sound cover and working frost protection is generally safer and simpler left running through a British winter, and Dorset's coastal winters are mild by national standards. Shut a hardshell down only if the power is going off, the property will be empty for a month or more, the tub sits somewhere exposed and unheated, or you genuinely will not use it. An inflatable is the opposite case: PVC liners go brittle in the cold, the heater runs almost constantly below ten degrees, and if you are not going to use it regularly the sensible move is to drain it, dry it and store it indoors.

Is it enough to just drain my hot tub for winter?

No, and this is the single most expensive misunderstanding in hot tub ownership. Opening the drain valve empties the shell, but it leaves water sitting in the jet lines, the heater tube, the pump housing and every low spot in the plumbing. That trapped water is exactly what freezes, expands and splits fittings. An empty but unwinterised tub is arguably at higher risk than a running one, because there is no heater and no circulation protecting it. You must blow the lines out with a wet and dry vacuum and add non-toxic antifreeze to the low points.

When should I winterise my hot tub in Dorset?

Late October to early November, before the first hard frost. Doing it early means you are working on a dry day in reasonable temperatures rather than wrestling a hose with frozen hands in December. Pick a day above five degrees and check that no hard frost is forecast in the next forty eight hours, because the job takes two to three hours and you do not want to be halfway through a drain-down when the temperature drops.

What does freeze damage to a hot tub actually cost?

Far more than the winterisation. A cracked pump housing on a hardshell runs into the hundreds to replace, and split plumbing means stripping and replumbing sections of pipework, which is largely labour. On an inflatable, a frost-damaged pump unit is typically one hundred to two hundred pounds, and a liner that has cracked at a seam in the cold usually cannot be economically repaired. Against that, a DIY winterisation costs perhaps twenty five to forty pounds in flush, antifreeze and a fresh filter.

Can I use ordinary car antifreeze in my hot tub pipes?

Absolutely not. Automotive antifreeze is ethylene glycol, which is highly toxic and tastes sweet, so it is a genuine poisoning risk to cats, dogs, hedgehogs and garden wildlife. Vets treat animals for antifreeze poisoning every winter. Use only non-toxic propylene glycol antifreeze sold for pools and spas. It costs roughly the same and is sold by any hot tub supplier.

Is it cheaper to run a hot tub through winter or shut it down?

Purely on electricity, shutting down wins if you will not use the tub for three months or more. A well insulated hardshell costs somewhere in the region of forty five to ninety pounds a month to run through winter, while a standard inflatable is considerably more because the heater fights a much bigger temperature gap with much less insulation. Winterising is a one-off cost of tens of pounds. But that arithmetic only holds if you genuinely would not have used it, and if you do the drain-down properly. One freeze failure wipes out several winters of savings.

Hot Tub Winterising & Drain Down: The Dorset Guide

Should you shut it down or run it through? The honest answer depends on which tub you own — and the step almost everyone skips is the one that actually prevents the damage.

Every October the same question lands: the evenings have turned, the tub hasn't been used in a fortnight, and you're standing on the patio wondering whether to drain it or leave it running. Get it wrong in either direction and it's expensive — a winter of needless electricity on one side, a split pump manifold on the other.

The good news for Dorset owners is that our winters are genuinely mild by UK standards. The coast rarely sees a sustained hard freeze, and a properly covered, powered hardshell will shrug off most of what a Bournemouth winter throws at it. The catch is that inland — out toward Wimborne, Verwood and the heathland frost pockets — clear still nights drop several degrees below what the seafront records. And the tubs most at risk out there are exactly the ones sitting on long exposed leads in big rural gardens.

First, the Decision: Run It or Shut It Down?

This is where most guides go wrong: they assume you're winterising, and launch straight into the drain-down. For a lot of owners that's the wrong advice. The correct answer splits cleanly by tub type.

🛁 Hardshell / acrylic spa — usually LEAVE IT RUNNING

Hardshell tubs are built to live outdoors year-round. High-density foam insulation, a thick cabinet, and a control pack with frost protection that automatically circulates the water if it gets too cold. Running one through a mild winter costs less than people expect, and the water moving through the pipes is itself the best protection you have.

Only winterise a hardshell if:

The power is going off — frost protection is worthless without electricity.
The property will be empty for a month or more (holiday let, second home, long trip).
The tub is somewhere exposed and unheated and genuinely won't be used.
You've had repeated freeze events that beat the insulation even with the cover on.

💨 Inflatable (Lay-Z-Spa, Intex, MSpa, CleverSpa) — usually DRAIN AND STORE

Inflatables are the opposite case. There's very little insulation, so below about 10°C the heater runs almost permanently and your bill climbs steeply. Worse, PVC and vinyl go brittle in the cold — a hard frost can crack seams and weaken glued joints even on an empty tub.

If you'll use it most weeks through the winter, you can keep it up: Freeze Shield (or your brand's equivalent) holds the water above freezing, but only while it's powered and full. If you won't use it regularly, drain it, dry it thoroughly and store it indoors. And if you're going away over Christmas and the temperature could drop, take it down first — Bestway say so themselves.

⚠️ The one option that is never right

Leaving the tub full of water with the power switched off. This is the classic disaster. Without circulation or a heater, the standing water in the narrow internal pipework can freeze solid in a matter of hours — long before the big body of water in the shell would. Ice expands, and you get a burst pipe or a cracked pump manifold. If the power's coming off, the water comes out. No exceptions.

What Freeze Damage Actually Costs

It's worth being blunt about the numbers, because the whole decision turns on them.

Outcome	Typical cost
DIY winterisation (flush, antifreeze, fresh filter)	£25–£40
Professional drain-down service	£80–£150+
Frost-damaged inflatable pump unit	£100–£200
Cracked liner seam (inflatable)	Usually not economic to repair
Cracked hardshell pump housing	Several hundred
Split plumbing — strip & replumb sections	Mostly labour, and a lot of it

The pattern is the same every year: someone drains the tub, walks away satisfied, and finds a puddle on the patio in February. Draining is not winterising. Which brings us to the step that matters most.

The Step Everyone Skips: Blowing Out the Lines

"I drained it" almost always means "I opened the drain valve and went inside." Gravity draining empties the shell. It does not empty the jet lines, the heater tube, the pump housing, or any low point in the plumbing — and that residual water is precisely what freezes.

A wet & dry vacuum in blow mode is the tool for this. Hold the nozzle against each jet opening for 10–15 seconds; you'll hear water spluttering out of the other jets as the air pushes it through the loop. If you're using an air compressor instead, keep it below 30 PSI — higher pressure damages seals and fittings, and you'll have traded a freeze risk for a leak.

Full Drain-Down, Step by Step

Allow two to three hours. Pick a dry day above 5°C, check no hard frost is forecast for 48 hours, and turn the heater off a couple of hours beforehand so you're not sluicing 38°C water across the patio.

Flush the pipework while it's still full. Add a pipe flush product, run the jets on maximum for 20–30 minutes with the cover off, and skim off what comes up. It is as revolting as it sounds, and that's the point — that biofilm would otherwise sit in your pipes until spring.
Isolate the power. Unplug a 13A plug-and-play tub and seal the plug end in a bag; switch off the breaker on a hardwired spa. Confirm the topside panel is dark before going further.
Drain the shell. Hose from the drain valve to a proper drain — not the flower beds, since chlorine and bromine residue kills plants. A submersible pump turns a 2–3 hour gravity drain into 20–30 minutes.
Mop the low spots. Footwell, seats, filter housing. Unscrew the jet inserts (most twist out anticlockwise) so water behind them can escape.
Blow out the lines — as above. Don't skip it.
Drain the pump and heater. Open the pump unions and tilt to let the last water out; open the heater drain plug if fitted. Blower-equipped spas: briefly restore power, run the blower ~10 seconds to clear the air channels, then isolate again.
Antifreeze the low points. 100–200ml of non-toxic propylene glycol spa antifreeze into each jet, the pump unions, and the drain valve last. You're coating, not filling.
Clean and dry. Non-abrasive cleaner on the shell so residues can't harden. Remove the filters — clean and dry them, or just replace them come spring.
Leave the drain valve open all winter so condensation escapes rather than pools.
Cover and protect. Insulated cover on and strapped down, tarpaulin or winter cover over the top. Mesh over any open pipework if you've removed equipment — rodents and insects will find it otherwise.

☠️ Never use car antifreeze

Automotive antifreeze is ethylene glycol. It's highly toxic and it tastes sweet, which is why vets treat poisoned cats, dogs and hedgehogs every single winter. Use only propylene glycol antifreeze sold for pools and spas. It costs about the same and any hot tub supplier stocks it.

Storing an Inflatable Properly

Bestway's own storage guidance is clear and worth following to the letter, because most inflatable "winter" failures are really storage failures:

Completely dry before packing. Any damp left in the folds becomes mould over four months. Leave it out in the sun for a few hours if you can.
Store indoors at a moderate temperature — roughly 15–38°C. A frost-free garage or shed is fine; an unheated outbuilding that dips below freezing is not.
Don't pack down in the cold. Near-freezing PVC is brittle and will crack as you fold it. Same reason you don't set up in a hard frost.
The pump goes indoors too. Its internal passages hold water that's near impossible to fully drain, which is why frost damage to the pump is the most common inflatable winter failure.
Clean the filter housing and bin the old cartridge. You'll want a fresh one in spring regardless.

If You're Keeping It Running

Chose to run through winter? Then the job changes from draining to defending:

Check the cover. This is the single biggest lever. A waterlogged, sagging cover more than about five years old is leaking money every night and raising your freeze risk. Replace it before winter, not after.
Add a floating thermal blanket under the cover — a meaningful cut in heat loss for very little money.
Insulate the base on an inflatable. A thick foam heat mat matters far more once the ground is cold.
Keep the temperature steady at around 37–39°C rather than dropping it and reheating. Heat-up cycles from cold are what actually burn the electricity.
Confirm frost protection is enabled on a hardshell, and check the tub weekly through the coldest months.
Expect to top up more, not less. Winter evaporation is high — a dropping water level in January is usually evaporation, not a leak.
Watch for a power cut. More than a day or two without power in a freeze is the real danger for a running tub.

Do the Descale Now, Not in April

Here's the bit of timing that saves people money. A drain-down is the single best moment of the year to descale. The tub is already empty, the pump is already disconnected, and you've got hours of dead time while things dry. In Dorset's 295 mg/l water that matters more than almost anywhere in the country — see our hard water and limescale guide for why, and how to descale a Lay-Z-Spa for the method.

Descale on the way down and your spring startup becomes a fill-and-go rather than a fortnight of chasing an E02 flow error through a scaled heater. Do it the other way round and you're doing the fiddly work in March, in a hurry, when you actually want to be in the tub.

When to Get an Engineer In

Most owners can handle a drain-down themselves. Call someone if:

You've no way to blow the lines out and the tub is a hardshell with complex plumbing — that's exactly the plumbing that's expensive to repair.
The tub is already showing faults going into winter — not heating, tripping the electrics, or not holding temperature. Shutting a faulty tub away for four months doesn't fix it; it just delays the bill.
You suspect frost has already got to it. Turn the power off and call someone — do not pour hot water on frozen pipes, as the thermal shock cracks the very components you're trying to save.
You'd rather it was simply done right. Our annual servicing covers the drain-down, descale and full system check in one visit.

Covering Poole · Christchurch · Wimborne · Ferndown · Ringwood · Verwood · Bournemouth — full areas guide.

Book a Winter Drain-Down

Drain, pipe flush, lines blown out, descale and a full system check — done properly before the frost. Tell us your model and postcode for a price.

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Winterising Quick Facts

✅ Late Oct–early Nov, before first frost
✅ Hardshell: usually leave it running
✅ Inflatable: drain, dry, store indoors
❌ Never leave it full and powered off
❌ Never use car antifreeze
✅ Blow the lines out — the key step
✅ Leave the drain valve open

Not Sure Whether to Shut It Down?

We winterise across Bournemouth, Poole and Dorset — and we'll tell you honestly if your tub is better left running. Either way it gets descaled and checked before the cold sets in.

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