Cold Plunge Water Treatment: How Often to Change the Water

What keeps a plunge usable is some mix of three jobs: a filter catching hair and grime, a sanitizer dealing with what a filter lets through, and fresh water when both fall behind. Filters alone don't sanitize. Sun Home is blunt about it: bacteria and dissolved organics pass through most cartridge filters.

Change schedules by setup

These intervals are Sun Home's, for home use. Heavy use or an uncovered tub outdoors pushes toward the short end.

What the makers ask for

Your tub's own manual wins over any general schedule, because warranty terms follow it. Plunge's minimums for the residential All-In:

• Weekly: skim the water, clear the drain screens, wipe the waterline and test the water chemistry.
• Monthly: change the filter.
• Every 6 months: change the water and deep clean, or every 1 to 3 months if you skip Plunge's water chemicals.

Chilled tubs from Renu and others pair a filter with an ozone generator. Renu's own troubleshooting uses the ozone bubbles at the jet as a flow check: few bubbles usually means the filter needs changing.

Which sanitizer

• Ozone is built into many chilled tubs. It runs on its own and adds nothing you have to measure, but it stretches water changes rather than replacing them, and Sun Home notes ozone generators need upkeep and ventilation.
• UV works on water passing the lamp. Bulbs and the quartz sleeve need periodic replacement and cleaning.
• Hydrogen peroxide is cheap and leaves little behind, but breaks down quickly, so it suits a tub you drain every few weeks anyway.
• Chlorine or bromine gives the longest intervals, at the cost of testing and dosing like a hot tub.

Common questions

How often should you change cold plunge water?

Sun Home's schedule: every 2 to 5 days with no filter, every 5 to 10 days with a basic pump and cartridge filter, every 2 to 3 weeks with ozone or UV, and every 8 to 12 weeks with a filter plus chlorine or bromine kept at 1 to 3 ppm. Plunge's own minimum for the residential All-In is every 6 months with its water maintenance chemicals, or every 1 to 3 months without them.

Does ozone mean you never have to change the water?

No. Ozone and UV stretch the time between changes; they don't end them. Sun Home notes that dissolved solids build up in any tub and eventually force a full drain however good the filtration is.

Can you put chlorine in a cold plunge?

Some owners run their tub like a spa. Sun Home's numbers for that setup are 1 to 3 ppm free chlorine and pH 7.2 to 7.8, with a drain and refill every 8 to 12 weeks at 3 to 5 plunges a week. Check your tub's manual first: makers that sell their own water chemicals, like Plunge, write their protocol around those.

Is hydrogen peroxide enough to keep plunge water clean?

It helps for a while. Sun Home's guidance is that food-grade peroxide breaks down quickly, and pairs a filter and diluted peroxide in a covered tub with a water change every 2 to 4 weeks and a weekly look at the water.

How often should I change the water in an Ice Barrel?

The Ice Barrel 500 product guide on Rogue's site says every 1 to 4 weeks without a filtration system, with the inside wiped down between refills.