For a single user with filtration and a sanitiser, change ice bath water every 2 to 4 weeks. With no treatment at all, drain and refill after 3 to 5 uses or within 7 days, whichever comes first. For shared club, academy or gym use, the safe default is emptying and cleaning the tub after every session unless the unit has recirculating filtration and a measurable disinfectant residual you test daily. Cold water does not keep itself clean, and the assumption that it does is the single biggest hygiene mistake in team recovery setups.
How often should you change ice bath water?
Water change frequency depends on three things: how many people use the tub, whether it has filtration, and whether you maintain a measurable disinfectant residual. A single-user tub with a filter and an oxidiser can run for weeks. A shared tub with neither should be emptied daily at minimum, and after each session where bather load is high.
| Setup | Users | Change water | Also required |
|---|---|---|---|
| No filtration, no sanitiser | 1 person | Every 3 to 5 uses, or 7 days | Wipe down and dry the tub after draining |
| Filter plus sanitiser | 1 person | Every 2 to 4 weeks | Test residual weekly, rinse filter fortnightly |
| No filtration, no sanitiser | Squad or multi-user | After every session | Clean and dry between fills, no exceptions |
| Filter plus sanitiser | Squad or multi-user | Weekly, or sooner on heavy use | Test residual and pH daily, log the readings |
| Any setup showing cloudiness, odour or film | Any | Immediately | Full drain, clean, disinfect and refill |
Those are working defaults, not regulations. If your tub is in a commercial or club setting, the governing documents are PWTAG Technical Note 71 and the BISHTA and SPATA cold water immersion guidance, covered further down.
Does cold water stop bacteria growing?
Cold slows bacterial growth but does not eliminate the organisms already in the water, and it actively works against you in one important way: low temperatures reduce the effectiveness of chlorine and bromine. So the water gets less protection precisely because it is cold, which is the opposite of what most people assume.
Research cited in the 2024 evidence brief on cold plunge tanks from Canada's National Collaborating Centre for Environmental Health found that both E. coli O157:H7 and Salmonella Typhimurium survived at 4°C, even though their growth was inhibited. Survival is the relevant outcome for a shared tub. A pathogen that is not multiplying can still infect the next person in.
What does the research actually show about shared ice baths?
Only one study of microbiological hazards in cold plunge tanks was identified in that 2024 review, and its findings are stark. Water samples from fixed tanks hard-plumbed into recirculating filtration and automatic disinfection systems came back clean in 87% of cases, with seven of eight samples negative for E. coli and coliforms, Pseudomonas aeruginosa and Staphylococcus aureus.
Mobile inflatable tubs told a different story. Those tubs had chlorine added manually but no filtration or automatic dosing, and were drained just once a day. 64% of water samples were positive for one or more of the same organisms, despite residual chlorine readings ranging from 0.05 to 4.01 mg/L. Manual dosing with high bather load did not hold the line.
The outbreak record backs this up. A methicillin-resistant Staphylococcus aureus outbreak in an Australian professional football squad identified poor hygiene practices in shared facilities, including a shared ice bath, as a potential risk factor. A separate Public Health England investigation into an MSSA outbreak in a rugby team pointed to shared towels, razors and ice baths as likely contributors.
There is a less comfortable data point worth stating plainly, because it explains why "just top it up" is not a policy. A survey of distance runners found 12% had experienced faecal incontinence while running. Athletes go into recovery tubs straight off the pitch or the track. Assume the water is receiving whatever is on the skin.
What sanitiser levels should a cold plunge run at?
If you hold a residual, the standard targets are free chlorine or bromine at 1 to 3 ppm with pH between 7.2 and 7.6. Cold reduces disinfectant activity, so a residual that would be comfortable in a swimming pool is doing less work at 12°C than the number suggests.
Two things matter more than the exact figure. First, test with a photometer or a comparator rather than test strips: the BISHTA and SPATA guidance flags that strips can read inaccurately in cold water. Second, UV and ozone do not replace a residual. Both only act on water passing through the chamber or at the point of injection, which is why the 2023 Model Aquatic Health Code requires chlorine or bromine alongside them and prohibits UV combined with hydrogen peroxide in aquatic facilities.
Where each method fits
| Method | What it does | What it does not do |
|---|---|---|
| Chlorine or bromine | Provides a continuous residual throughout the body of water | Loses potency in cold water and burns off under high bather load |
| UV-C | Inactivates microbes as water passes the lamp | Nothing to water sitting in the tub; no residual protection |
| Ozone | Strong oxidation, good for high-use commercial tubs | Does not remove dissolved solids, still needs a residual sanitiser |
| Cartridge filtration | Removes hair, skin and visible debris, keeps water clear | Typically 20 micron, so it will not capture Cryptosporidium or Giardia |
| Draining and cleaning | The only reliable reset for dissolved solids and biofilm | Nothing, if the surfaces are not scrubbed and dried afterwards |
Does filtration mean you can skip water changes?
No. Filtration handles particulates, not dissolved load. Most cold plunge filters are around 20 microns, and removing protozoa such as Cryptosporidium and Giardia requires a pore size of 1 micron or less. Meanwhile total dissolved solids climb steadily with every session, and no amount of ozone removes them.
Filtration extends the interval between changes. It does not abolish it. A filtered, sanitised, single-user tub still needs a full drain and clean on a schedule, and any tub in shared use needs one considerably more often than its owner would like.
What do UK clubs and gyms actually have to follow?
Three documents matter for commercial and club settings in the UK. PWTAG published Technical Note 71 on ice baths in August 2024, written with commercial operations as the focus. BISHTA and SPATA released cold water immersion industry guidance in 2025, developed with a cross-industry working group and research input from Coventry University. Both sit alongside HSE guidance HSG282 on controlling legionella and other infectious agents in spa pool systems.
The BISHTA and SPATA guidance draws a distinction that resolves most of the confusion around water changes. It defines two product categories: cold water immersion baths, which are emptied after each use, and cold water immersion spas, which retain water over longer periods. Which category your unit falls into determines the entire water treatment regime. Get that classification right first, then build the protocol around it.
HSG282 is not itself law, but following it is generally accepted as demonstrating compliance. For an academy, NGB or clinic, that is the practical bar: a documented regime, logged readings, and a named person responsible for it.
What does a workable maintenance schedule look like?
The schedule below is a starting point for a club or clinic running a cold plunge as part of a recovery room. Adjust the frequency upward if bather load is high, and treat every line as something that gets written down rather than remembered.
| Frequency | Task |
|---|---|
| Before each session | Check water temperature against the 11-15°C target with a calibrated thermometer; visual check for cloudiness, film or odour |
| Daily (shared use) | Test free chlorine or bromine and pH with a photometer or comparator; log both readings |
| After each session (unfiltered tubs) | Drain, wipe surfaces, dry the tub, cover it |
| Weekly | Rinse or replace the filter cartridge; inspect seals, hoses and the cover |
| Weekly to monthly | Full drain, clean and refill, depending on setup and bather load |
| Quarterly | Deep clean including plumbing lines where fitted; replace filter cartridges; review the written regime |
| Always | Users shower before entry; no entry with open wounds, skin infections or recent gastrointestinal illness |
The pre-entry shower rule is the cheapest control on this list and the one most often skipped. It removes the organic load before it reaches the water, which is what your sanitiser would otherwise be spending itself on. For screening, supervision and contraindications, see our guide to cold water immersion safety.
How does this apply to a Plunge PRO?
A Plunge PRO at £295 is a drain-and-refill unit rather than a plumbed, recirculating spa, which places it in the cold water immersion bath category under the BISHTA and SPATA framework. That is a feature, not a limitation: emptying and refilling is the most reliable hygiene control available, and it removes the need to manage a residual and a filtration loop.
Practically, that means a single user can run 3 to 5 sessions before a change, and a squad setup should drain and clean between groups. Wipe the interior down, let it dry, and keep it covered between uses. Clubs pairing a Plunge PRO with Pulse PRO compression boots get a recovery station with no shared water at all on the compression side, which simplifies the hygiene picture considerably compared with a wet-only setup.
Academies, NGBs and clinics specifying recovery equipment at scale can look at the MyVYRO partner programme, which covers bulk pricing and setup guidance for multi-unit installs.
Most inflatable tubs pair 5 cm walls with a fabric cover. The Plunge PRO pairs rigid drop-stitch walls with a rigid inflatable lid, and sets up in minutes with no plumbing.
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Written by Jonny, founder of MyVYRO. Former academy footballer and American Football athlete, retired at 29 through injury. MyVYRO was built because the industry standardised on average, and he refused to.