Cold Plunge in Winter: Keep It Running or Winterize

Winter is when a lot of people want to plunge outdoors, and when the equipment is most at risk. The risk is water freezing solid inside the tub or in the plumbing and chiller.

Option 1: keep it running

Ice Barrel's advice for the Ice Barrel 500 in a freezing climate is to keep the water moving with a pump or chiller. A tub with a heater option, like the Plunge All-In ($10,490 with the heater, Oct 27, 2026), can also hold the water above freezing. If power drops during a cold snap, though, nothing is moving, so this works best where outages are rare or someone checks the tub.

Water in a cold, covered outdoor tub also stays usable longer. Sun Home's guidance for an unfiltered tub in winter, with near-freezing water and little debris, stretches the usual 2 to 5 day change to 5 to 7 days if the water still looks and smells clean.

Option 2: drain and winterize

Plunge says the only guaranteed protection is moving the tub somewhere temperature controlled. For owners who leave an All-In outside, its residential procedure is, in short:

1. Pause and unplug the tub, take out the filter and clean the canister.
2. Drain the tub from the main drain, then open the other drains (up to two more) so the whole system is empty.
3. Pour in the one antifreeze concentrate Plunge specifies, mixed three parts water to one part antifreeze.
4. Plug back in and set the temperature to 90°F so the chiller does not try to run while the pump primes, then let the pump circulate the mix for 10 minutes.
5. Open each drain briefly until the water runs pink, then cap them and remove the leftover solution.
6. Strap the cover on. Unplug the GFCI and store it somewhere dry.

Other tubs have different drains and plumbing, so follow your own maker's steps. An unpowered tub or barrel is simpler: drain it fully before a hard freeze if it will sit unused.

Common questions

Can a cold plunge freeze?

Yes. Ice Barrel's guidance for the Ice Barrel 500 is that it can be used in freezing temperatures, but water that freezes solid can expand and damage the barrel. Plunge says all its cold plunges must be winterized in freezing conditions, 32°F or below, to avoid damage and keep the warranty.

Can I keep using my cold plunge outside in winter?

It depends on the maker. For the Ice Barrel 500 the advice is to keep the water moving with a pump or chiller, or drain it if it will sit unused. Plunge's position is that the only sure protection is moving the tub somewhere temperature controlled; outdoors in freezing weather it has to be winterized.

What antifreeze do you use to winterize a cold plunge?

Use only what your maker names. Plunge specifies one concentrate for the All-In, mixed three parts water to one part antifreeze, and warns that any other product may damage the system and be hazardous in a plunge.

Does a cold plunge use less power or ice in winter?

Colder surroundings mean less heat leaking into the water, so a chiller or a bag of ice has less to fight. The catch is the freezing risk above, which a warm-weather setup never has to think about.