Cold Plunges
Cold plunge maintenance: keeping the water usable
A plunge is standing water you sweat into several times a week. Here is the routine that keeps it clear, and the equipment that does the work.
By Scooter M. · Published · Last updated
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| # | Product | Rated watts | Best for | Score | Price |
|---|---|---|---|---|---|
| 1 |  AquaDoc Cold Plunge Water Treatment, 32 oz A weekly treatment dosed at 1 oz per 100 gallons, which is the maintenance step most first-time plungers skip until the water turns. | Not published | Keeping the water usable | 5.0 | Check price |
| 2 |  600 GPH Cold Plunge Filter with UV Sanitation A 600 GPH pump and filter with UV sanitation for tubs from 300 to 1,000 gallons, for anyone running ice rather than a chiller. | Not published | Filtration without a chiller | 1.0 | Check price |
| 3 |  AS ColdPlunge 1/3 HP Cold Plunge Chiller 600 W, a 42 F floor, a reusable metal filter instead of cartridges, and a submersible pump in the box so it works with a bathtub that has no ports. | 600 W | Best for a bathtub | 7.7 | Check price |
The routine, in order of how much it matters
- Rinse before you get in. Free, and the single biggest factor.
- Keep the lid on whenever you are not in the tub.
- Run filtration - built into most chillers, a separate pump if you are on ice.
- Dose weekly, typically 1 oz of treatment per 100 gallons.
- Drain and refill every four to eight weeks, through a hose, not by tipping.
Why cold is not a substitute for cleaning
Cold slows bacterial growth. It does not stop it, and it does nothing at all about the body oils, skin cells, sunscreen and sweat that arrive with every session. A hundred gallons receiving four bodies a week without filtration will go cloudy inside a fortnight, then it will smell, and the usual response is to drain the whole thing - which is wasteful, tedious and the reason a lot of people stop plunging.
The rinse-before-you-get-in step is worth repeating because it is free and it is the one people skip. If you are coming straight out of a sauna, you are carrying a session’s worth of sweat into the water. Thirty seconds under a shower prevents more fouling than any equipment on this page.
Filtration: what a chiller gives you for free
Most chillers in our roundup include filtration, and the type matters more than the presence:
The reusable-versus-cartridge distinction is a real running cost that never appears in a comparison because it is not electricity. Over three years the difference between rinsing a metal screen and buying cartridges is larger than the difference in power draw between two chillers. Which chillers publish their filtration covers it in detail.
Chemical treatment, dosed properly
Weekly treatment products for plunge water are typically dosed at about one ounce per hundred gallons. That instruction is only useful if you know your volume - which brings us back to the capacity problem covered in the inflatable roundup, where two listings publish two different capacities on the same page.
If your tub’s published capacity is ambiguous, fill it once through a hose with a flow meter, or fill it in measured buckets the first time. It takes one afternoon and it makes every dosing decision afterwards correct rather than approximate.
Draining without a wet floor
A hundred gallons weighs about 830 pounds. It is not being tipped. Every tub worth buying has either a side drain with a hose fitting or inlet and outlet ports that double as one, and if yours does not, a submersible pump and a hose to a drain is the retrofit.
One tub in our roundup ships with a three-foot drain hose and makes a feature of the side drain. That is the correct instinct: the difference between a tub you refresh every six weeks and one you do not is entirely about how annoying the drain is.
Freezing, if it lives outside
Two failure modes, both avoidable. Water left in a chiller and its hoses can freeze and split them, so drain the loop if you are shutting down for winter. And fabric that is not rated for low temperatures can go brittle - one tub in our roundup publishes a material tolerance of minus 4 F to 140 F, and it is the only one that publishes anything at all on the question. If you are leaving a tub outside through a hard frost, either keep the chiller running or drain it completely.
Every pick, in full
Each write-up below shows the score broken into its six components, the specs the listing actually publishes, and the running-cost arithmetic where a wattage exists to compute it from.
#1 - Keeping the water usable
AquaDoc Cold Plunge Water Treatment, 32 oz
A weekly treatment dosed at 1 oz per 100 gallons, which is the maintenance step most first-time plungers skip until the water turns.
| Small-space fit | 8 / 20 |
|---|---|
| Electrical fit | 20 / 20 |
| Cost to run | 20 / 20 |
| Key-number disclosure | 0 / 15 |
| Spec completeness | 2 / 15 |
| Warranty | 0 / 10 |
| Total | 50 / 100 |
| Rated watts | Not published Not published |
|---|---|
| Maximum temperature | Not published Not published |
| Dimensions | Not published Not published |
| Weight | 2 lb Seller’s listing, read 2026-09-07 |
| Timer | Not published Not published |
| Cooling floor | Not the relevant number for this category |
| Material | Not published Not published |
| Warranty (months) | Not published Not published |
No electrical load. This draws no power of its own. The running cost of a plunge lives in the chiller, or in the bag of ice.
A cold plunge is a body of standing water at a temperature that slows bacterial growth without stopping it, with body oils and skin cells going into it several times a week. Left alone it goes cloudy and then it smells, and the usual response is to drain and refill a hundred gallons, which is both wasteful and the reason people quit.
The dose is published clearly at one ounce per hundred gallons weekly, which is the sort of instruction you can actually follow. Whether you use this product or another, chemical treatment plus a filter is what turns a plunge from a weekly refill chore into something that runs for weeks.
Buy it if
Anyone who owns a plunge tub and has not yet worked out why the water goes cloudy.
Skip it if
You drain and refill after every session anyway.
#2 - Filtration without a chiller
600 GPH Cold Plunge Filter with UV Sanitation
A 600 GPH pump and filter with UV sanitation for tubs from 300 to 1,000 gallons, for anyone running ice rather than a chiller.
| Small-space fit | 8 / 20 |
|---|---|
| Electrical fit | 0 / 20 |
| Cost to run | 0 / 20 |
| Key-number disclosure | 0 / 15 |
| Spec completeness | 2 / 15 |
| Warranty | 0 / 10 |
| Total | 10 / 100 |
| Rated watts | Not published Not published |
|---|---|
| Maximum temperature | Not published Not published |
| Dimensions | Not published Not published |
| Weight | Not published Not published |
| Timer | Not published Not published |
| Cooling floor | Not the relevant number for this category |
| Material | Not published Not published |
| Warranty (months) | Not published Not published |
No running cost can be computed. The listing does not publish a rated wattage, so there is no honest way to tell you what a session costs. We will not estimate one. How we compute running costs
Chillers come with filtration built in. Ice does not, which leaves ice-only plungers with the same water quality problem and none of the equipment, and it is why a standalone filter belongs in this category rather than being an afterthought.
Six hundred gallons per hour turns over a 100-gallon tub six times an hour, which is well above what a plunge needs, and the UV stage handles what a mechanical filter cannot. Running it for an hour after each session is enough to keep water clear for weeks.
The wattage is not published, so we cannot give you a running cost, but a pump in this class is a small load - tens of watts rather than hundreds - and it runs for an hour rather than continuously.
Buy it if
An ice-only plunger whose water is going cloudy between refills.
Skip it if
Your chiller already includes filtration. Most in this roundup do.
#3 - Best for a bathtub
AS ColdPlunge 1/3 HP Cold Plunge Chiller
600 W, a 42 F floor, a reusable metal filter instead of cartridges, and a submersible pump in the box so it works with a bathtub that has no ports.
| Small-space fit | 12 / 20 |
|---|---|
| Electrical fit | 20 / 20 |
| Cost to run | 16 / 20 |
| Key-number disclosure | 12 / 15 |
| Spec completeness | 11 / 15 |
| Warranty | 6 / 10 |
| Total | 77 / 100 |
| Rated watts | 600 Seller’s listing, read 2026-09-07 |
|---|---|
| Water capacity | 79 Seller’s listing, read 2026-09-07 |
| Dimensions | 11.8 x 14.9 x 12.6 in Seller’s listing, read 2026-09-07 |
| Weight | 35 lb Seller’s listing, read 2026-09-07 |
| Cooling floor | 42 Fno cooling rate published Seller’s listing, read 2026-09-07 |
| Material | Not published Not published |
| Warranty (months) | 12 Seller’s listing, read 2026-09-07 |
| Rated draw | 600 W |
|---|---|
| Cost per hour at full draw | 11.0 cents |
| Upper bound, running continuously | $80.29 per month |
A chiller cycles. It draws its rated power while the compressor runs and almost nothing while it does not, and how often it runs depends on ambient temperature, insulation, lid use and setpoint. We do not measure duty cycle, so we publish the two figures that need no assumption and no figure in between. Computed at 18.34 cents per kWh (June 2026). The method.
The submersible pump is what makes this the bathtub answer. A chiller normally needs a tub with inlet and outlet ports; a bathtub has neither. Dropping a pump into the water and running two hoses over the rim is inelegant and it works, and it is the cheapest route to a cold plunge for anyone who cannot give up floor space for a tub at all.
Six hundred watts is eleven cents an hour at full draw, comfortably mid-range here. The 79-gallon rating is a good match for a standard bathtub, which holds somewhere between 40 and 80 gallons at plunge depth.
The reusable metal mesh filter rather than disposable cartridges is a genuine running-cost detail that gets ignored because it is not electricity. Cartridge filters are a recurring purchase; a rinsable metal screen is not, and over a year that difference is larger than the difference in power draw between two chillers.
Buy it if
Anyone plunging in an existing bathtub rather than buying a tub.
Skip it if
Your tub is over 79 gallons.
Questions people actually ask
How often should you change cold plunge water?
With filtration and weekly chemical treatment, most setups run for four to eight weeks between full changes. Without either, expect to change it weekly, because body oils and skin cells accumulate faster than cold alone can suppress them. A cover between sessions makes a large difference by keeping debris and light out.
How do you keep cold plunge water clean?
Three things in combination: mechanical filtration to catch hair and debris, a weekly chemical treatment dosed to your volume, and a lid on the tub whenever you are not in it. Chillers usually include the filtration; ice-only setups need a standalone pump and filter to get the same effect.
Do you need chemicals in a cold plunge?
If you want the water to last more than a week or two, yes. Cold slows bacterial growth, it does not stop it, and a body of standing water receiving skin oils several times a week will go cloudy. Products for this are typically dosed at about one ounce per hundred gallons weekly.
Should you shower before a cold plunge?
Yes, and it is the cheapest maintenance step there is. Most of what fouls plunge water arrives on your skin - oils, lotions, sunscreen, sweat from the sauna you just came out of. A thirty-second rinse before getting in does more for water clarity than any filter.