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Match water care to the equipment. Follow the instructions for your exact tub, chiller and treatment product. A method described for a simple ice bath may be unsuitable for a powered system. Never mix treatment chemicals.
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Quick answer
Shower for one minute before every plunge, keep the tub covered, skim it, and keep a sanitizer in the water that your tub's maker allows: hydrogen peroxide, spa chlorine or bromine for most DIY tubs, and the maker's own treatment where the manual names one (Icetubs owners use AquaFinesse only). Test at least twice a week. Drain on a schedule: gallons divided by 3, divided by plunges per day, is the most days a filtered, sanitized tub should go. A 100-gallon tub used once a day tops out around a month. With no filter, think days, not weeks.
Why plunge water goes bad.
You are the main contaminant. Every plunge leaves sweat, skin oils, dead skin, hair, lotion and sunscreen in the water. CDC says a one-minute shower removes most of the dirt, sweat and oils that use up the chemicals meant to kill germs. The Icetubs operating manual makes the same point about sweat, oils, sunscreen and fake tan: rinse first and the filter and the treatment have less to fight.
Outdoor tubs add leaves, pollen, bugs and blown dust. All of it is food for bacteria and work for the filter.
Cold helps less than people assume. Low temperatures slow most bacteria, but they don't sterilize anything, and some species grow even at refrigerator temperatures (FDA's example is Listeria). CDC says Legionella grows best between 77 and 113°F and can grow as low as 68°F. That matters for hot-and-cold units like the Icetubs IceBarrel and the Kohler x Remedy Place ice bath: on the hot setting, they are hot tubs and need hot-tub care.
Cold slows your sanitizer, too. EPA's disinfection tables show free chlorine needs about four times the contact time at 41°F that it needs at 77°F. The chlorine guide has the full table.
Then there's biofilm, the slick layer that forms on walls, hoses and filter housings. Dissolved sanitizer doesn't scrub it off. CDC's hot tub guidance handles it by hand: vigorously scrub all surfaces each time the tub is drained. If the walls feel slimy, the water has already lost.
The routine.
Every plunge
- Rinse for one minute first. It's the cheapest water treatment you'll ever buy.
- Bring clean feet. Outdoors, wear sandals to the tub and step out of them at the edge.
- Skim before and after. Icetubs tells owners to remove leaves, hair and particles before and after each use. A fine-mesh net catches the hair a coarse leaf net lets through.
- Put the cover back on. It keeps debris out and keeps kids and animals from falling in.
Twice a week
- Test. Read pH and your sanitizer. Leisure Time's spa chlorine label says to test every 2 to 3 days and after heavy use.
- Dose to the target. Peroxide, chlorine or bromine, whichever your manual allows. Targets are in the table below.
- Wipe the waterline. Body oil collects there first. Icetubs recommends a damp microfiber cloth, with a little baking soda (sodium bicarbonate) for stubborn scum, rubbed with the grain on stainless steel.
Every one to four weeks
- Rinse or replace the filter cartridge on your maker's schedule. Intex says every two weeks for its pool cartridges; Icetubs and Kohler say monthly for home use. The filter guide has every schedule in one table.
- Shock if you use chlorine. Leisure Time's Spa 56 label calls for a double dose every 2 to 4 weeks with the cover off, and nobody in until free chlorine falls back to 2 to 3 ppm.
Every drain
- Scrub, rinse, refill, re-dose. The steps are further down.
How often to drain, by tub size.
Hot tub makers use a simple formula and it transfers to plunges. Jacuzzi's version: gallons divided by 3, divided by the average number of daily users, equals days between water changes. It assumes the water is filtered and sanitized, so read the result as a ceiling, not a goal.
Most days between water changes for a filtered, sanitized tub (gallons divided by 3, divided by plunges per day)
| Tub size | 1 plunge a day | 2 a day | 4 a day |
|---|---|---|---|
| 80 gallons | 27 days | 13 days | 7 days |
| 100 gallons | 33 days | 17 days | 8 days |
| 125 gallons | 42 days | 21 days | 10 days |
| 150 gallons | 50 days | 25 days | 12 days |
| 200 gallons | 67 days | 33 days | 17 days |
Makers cap it lower. The Icetubs manual says 1 to 2 months with the engine running and one person plunging daily. Kohler says every 1 to 2 months or as needed. Ice Barrel's 3-in-1 label says every 4 to 6 weeks. Use whichever number is smallest.
No filter means more drains. Nothing removes what you leave behind, so the formula doesn't apply. San Francisco's health department tells businesses that unfiltered cold plunge water should be drained between users. At home, with one person and a sanitizer, our rule of thumb is a fresh fill every 3 to 7 days, and sooner the moment the water looks or smells off. That's the honest answer to how to keep ice bath water clean without a filter: rinse, cover, skim, sanitize, and drain often.
Sanitizers compared.
Your tub's manual outranks this table. Icetubs, for one, prohibits chlorine and bromine outright and requires its own treatment.
What each water treatment does, and what it doesn't
| Option | What it does | What it doesn't do | Lasting residual | Watch for |
|---|---|---|---|---|
| Hydrogen peroxide (3%) | Oxidizes organic gunk and kills microbes in the water | No CDC or health-code target exists for it; dosing comes from our peroxide guide | Short; it breaks down to water and oxygen | Never with chlorine or bromine; with an ozone chiller, stay under its maker's peroxide limit; needs peroxide test strips |
| Chlorine (spa dichlor) | Kills bacteria and viruses; the chemical health codes are written around | Doesn't remove oils or particles; works slower in cold water | Yes, measurable free chlorine | Banned by some makers; builds cyanuric acid; chloramine smell |
| Bromine (tablets) | Same job as chlorine; CDC sets a 4 ppm floor for public hot tubs | Tablets need a floater, and floater output is set by testing, not the dial | Yes | Never with chlorine or biguanide products; banned by Icetubs |
| Ozone | Oxidizes organics and kills microbes in water passing the injector; built into Icetubs and Finnmark SoulCold | EPA says it decomposes rapidly, so nothing stays in the tub | No | Irritating gas trapped under covers; follow the chiller maker's rules on peroxide |
| UV-C | Kills microbes in water flowing past the lamp; built into the Kohler x Remedy Place ice bath | Treats nothing that stays in the tub | No | Needs flow and clear water; never look at the lamp |
| Enzymes | Break down body oils and lotions that make scum lines | SpaGuard's label says its enzyme is not a sanitizer and works alongside one, never in place of it | No | Still need a sanitizer |
| Copper conditioner (Ice Barrel 3-in-1) | Ice Barrel says it inhibits scale, scum lines, metal staining and odors | Its listing doesn't claim to kill germs | Not stated | Skip it in tubs whose maker names another treatment |
| Biguanide (PHMB) | A separate non-chlorine spa sanitizer chemistry (Baqua Spa and SoftSoak are brand names) | Can't share a tub with chlorine | Set by its own label | Leisure Time's chlorine label: never combine the two "under any circumstances" |
For the 3-in-1, Ice Barrel's label says ½ oz per 60 to 80 gallons at the first fill and ¼ oz weekly after that, with a water change every 4 to 6 weeks. Treat it as a conditioner alongside a sanitizer, not a replacement for one.
Test strips, and the numbers to aim for.
A strip only reads what it was built to read. Chlorine strips don't measure peroxide, and peroxide strips don't measure pH. Pick the strip that matches your sanitizer.
Targets for a home plunge, and who sets them
| Reading | Aim for | Source |
|---|---|---|
| Free chlorine | 2 to 4 ppm | Kohler's ice bath manual (2 to 4); Leisure Time Spa 56 label (2 to 3). CDC sets a 3 ppm minimum for public hot tubs. |
| Bromine | 2 to 4 ppm | Leisure Time's bromine directions for residential spas. CDC and San Francisco set a 4 ppm minimum for public tubs. |
| pH | 7.4 to 7.6 (7.2 to 7.8 acceptable) | Kohler for the tight range; CDC, San Francisco and Leisure Time for 7.2 to 7.8 |
| Total alkalinity | 80 to 120 ppm | Leisure Time's start-up directions |
| Cyanuric acid (chlorine users) | As low as you can keep it | CDC says stabilized chlorine products shouldn't be used in hot tubs because they slow disinfection. Washington's pool code caps public pools at 90 ppm. |
| Hydrogen peroxide | Start at 50 ppm; top up when it reads 30 or lower | Our peroxide guide. Equipment makers publish anywhere from 15 to 100 ppm, so a lower ceiling in your chiller manual wins. Read it with peroxide strips. |
| Clarity | A clear view of the bottom, no color | Kohler's water standard for its ice bath |
What to keep on the shelf.
Four things cover most DIY tubs: a sanitizer, the right strip for it, a strip for pH, and a net. Chlorine and bromine products are on the chlorine page; pumps, cartridges and UV are on the filter page.
Best for chlorine-free DIY tubs
3% Food Grade Hydrogen Peroxide (1 Gallon)
- Strength: 3%
- Size: 1 gallon (128 fl oz)
- Additives: no added stabilizers, per the listing
- Dose: about 21 fl oz per 100 gallons for 50 ppm (full chart)
At 3% you measure in cups, which makes a small tub hard to overshoot. One gallon covers about six fresh 100-gallon fills at the 50 ppm starting dose, before top-ups. It's sold as a general-purpose cleaner, not as a registered spa sanitizer, so the plunge dose comes from our peroxide chart rather than the bottle.
Skip it if: you own an Icetubs (AquaFinesse only), you already use chlorine, bromine or biguanide, or your chiller runs ozone and its maker hasn't approved peroxide.
Best for checking peroxide
Bartovation Hydrogen Peroxide H2O2 Test Strips, 0-100 ppm
- Range: 0 to 100 ppm
- Color blocks: 0, 1, 3, 10, 50 and 100 ppm
- Count: 100 strips
- Read time: dip 1 second, read at 10 seconds
The 10, 50 and 100 ppm blocks bracket the working range: start a fresh fill at 50, and top up once the color falls toward the 10 block (30 or lower). The listing names cold plunges and hot tubs among its uses. A chlorine strip can't give you this reading.
Skip it if: you sanitize with chlorine or bromine. And know the limits: between 10, 50 and 100 ppm you are estimating, so this is a range check, not a precise number.
Best for pH and chlorine or bromine
JNW Direct Pool Test Strips, 7 in 1, 100 Pack
- Reads: free chlorine, bromine, pH, alkalinity, hardness and cyanuric acid
- Count: 100 strips
- Read time: dip 2 seconds, read at 30 seconds
- Shelf life: use within 90 days of opening, per JNW
One strip covers everything a chlorine or bromine tub needs, including cyanuric acid, which is the reading that tells you dichlor has been building up. Peroxide users still need pH, and this gives it.
Skip it if: you want a strip that reads peroxide; this one doesn't. At twice a week you'll use about 26 strips in the 90 days JNW allows after opening.
Best for daily skimming
U.S. Pool Supply 5 Foot Leaf Skimmer Net with 4 Aluminum Pole Sections
- Frame: 11 x 12 inches
- Bag: 6 inches deep, ultra-fine mesh
- Pole: four 11.5-inch sections, 60 inches total
- Short mode: remove sections to use it as a hand net
Fine mesh is the point: it lifts hair and small debris, not just leaves. Pull the pole down to one or two sections and it reaches across a barrel or stock tank without clipping the walls. The listing says the plastic frame won't mar liners.
Skip it if: your problem is grit on the floor of the tub. A net only lifts what floats or what you can scoop.
When to just drain.
- You can't see the bottom clearly, or the water has a tint. That's Kohler's own standard for its ice bath.
- It smells. A strong "chlorine" smell is usually chloramines, per CDC, which means the chlorine is busy with what you left behind.
- The walls or the underside of the cover feel slimy. That's biofilm. Dosing won't scrub it off.
- Foam or an oily film comes back right after you skim it.
- The sanitizer won't hold. You dose to target and the strip reads zero again the next day.
- Cyanuric acid keeps climbing, if you use dichlor.
- After any bodily-fluid accident, or if someone used it while sick with diarrhea. In 100 gallons, draining is faster and surer than treating.
Deep clean when you drain.
- Unplug the chiller or pump before you start.
- Drain completely and pull the filter cartridge.
- Scrub every surface with a soft brush or cloth. CDC's hot tub guidance says to vigorously scrub all surfaces each time the tub is drained.
- Use only the cleaners your manual allows. Icetubs prohibits chlorine, acids and salts in or on its stainless tubs. SaunaLife's S1 manual allows regular household detergent with a soft cloth and rules out chlorine-containing cleaners and rough materials, which discolor the tub.
- Flush the plumbing on the maker's schedule. Finnmark's SoulCold manual calls for spa cleanser every 6 months: run it through the chiller for 2 hours, then drain and refill. Nobody bathes with cleanser in the water.
- Rinse well, refill, and dose the sanitizer before the first plunge.
Safety: Use one sanitizer system at a time and never pre-mix products. Peroxide destroys chlorine, chlorine and biguanide can't be combined, and Leisure Time's label warns that mixing dry chlorine with other chemicals, including other chlorine products, bromine or oxidizers, can cause violent reactions or fire. Add products straight to the tub water, store them in their original containers, and keep all of them away from children and pets. Unplug any pump or chiller you've rigged yourself before you get in, and plug it into a GFCI outlet.
FAQ
How do I keep ice bath water clean without a filter?
Shower first, keep it covered, skim every session, hold a sanitizer residual (peroxide near 50 ppm, or spa chlorine at 2 to 4 ppm), and drain every 3 to 7 days. Without a filter, the drain is your filter.
What can I put in my ice bath to keep it clean?
A sanitizer your tub's manual allows: hydrogen peroxide, spa chlorine or bromine for most DIY tubs, or the maker's own product where the manual names one. Enzymes and copper conditioners help with scum and scale, but they aren't sanitizers.
How often should I change my cold plunge water?
Divide gallons by 3, then by plunges per day: a 100-gallon tub used once daily gets about 33 days at most, filtered and sanitized. Icetubs and Kohler both cap it at 1 to 2 months; an unfiltered tub needs fresh water every few days.
Should I put chlorine in my cold plunge?
Only if the manual allows it; Icetubs prohibits it, while Kohler lists 2 to 4 ppm free chlorine for its ice bath. The chlorine guide has the doses and the rules.
How much hydrogen peroxide do I put in an ice bath?
About 21 fl oz (2⅔ cups) of 3% peroxide per 100 gallons puts a fresh fill near 50 ppm; top up when a peroxide strip reads 30 or lower. The peroxide chart covers other sizes and strengths, and never add it to water that has chlorine or bromine in it.
Why is my ice bath slimy?
That's biofilm on the walls, which means the sanitizer residual ran out at some point. Drain, scrub every surface, refill, and keep the residual from dropping to zero again.
Is Sirona Simply Sanitizer chlorine?
Its seller describes it as a non-chlorine, non-bromine sanitizer that's compatible with biguanide sanitizers and tested with Sirona's own strips. Don't add chlorine on top of it.
Does a chiller keep the water clean by itself?
No. A chiller with a filter and ozone removes particles and adds oxidation, but Icetubs still requires weekly treatment and a water refresh every 1 to 2 months. See the chiller guide for what each one includes.