The internet is full of conflicting advice. This is ours: the same standard our technicians follow on every service visit, written plain so you can keep your water right between our visits.
Test 2–3 times a week — more if you plunge daily or have guests over.
Your sanitizer. Low? Add a small scoop of the granules we left you. High? Just wait — leave the cover off for an hour and it drops on its own.
It naturally creeps up under the cover as the water sits. If it reads high, add a small dose of the pH-down we provided. That's it.
Cloudy or musty water means something's off — text us, don't just keep adding chemicals. Guessing usually makes it worse.
The short list that keeps your plunge clean and your equipment alive.
The most common question we get — and the answer is almost always "less often than a hot tub, more often than you'd think for commercial." Cold water is on your side: at 38–55°F bacteria grow slowly, sanitizer isn't being cooked off, and there's barely any evaporation. What actually drives it is how many people are getting in, relative to how little water a plunge holds (usually 100–150 gallons vs. ~400 in a hot tub).
| Your setup | Change the water |
|---|---|
| Filtered + ozone/UV + sanitizer normal home use | Every 3–6 months |
| Filtered + sanitizer, no ozone most home plunges | Every 2–3 months |
| Busy household several people daily, guests, training groups | Every 4–8 weeks |
| Commercial gym, studio, recovery centre, clinic | Weekly at minimum — more with real volume |
| Unfiltered barrel or stock tank no circulation | Every 1–2 weeks |
Always follow your manufacturer's spec first — if their manual gives an interval for your unit, that's the one that counts. The table above is our field guidance where the manual is silent.
Foam that won't clear (dissolved solids and body oils are saturated) · sanitizer that won't hold — you dose it and it's gone by morning · cloudy water that survives a shock and a clean filter · a filter that loads up in days instead of weeks · slimy walls or a musty smell — that one's biofilm, and it needs a full purge of the plumbing, not just fresh water.
Plenty of plunges run chlorine-free, and that's fine — but it changes how often the water has to come out, because most alternatives leave no residual in the tub.
| Instead of chlorine | What it actually does | Water changes |
|---|---|---|
| Ozone or UV | Treats water only as it passes through the unit. Nothing is left behind protecting the tub between circulation cycles — or while someone's actually in it. | Much more often — think weeks, not months |
| Hydrogen peroxide | A genuine sanitizer, but it breaks down quickly and needs testing and topping up far more often than chlorine. Never mix it with chlorine — they cancel each other out. | Similar to chlorine if you keep it dialed in |
| Mineral / copper-silver cartridges | A helper, not a sanitizer. Designed to reduce how much sanitizer you need, not replace it. | As per whatever residual you pair it with |
| Nothing at all | Then the plunge is a bath. That's a legitimate way to run one — but only if you treat it like bathwater. | Drain every few days |
Two things worth knowing before you go chlorine-free: most manufacturers require a sanitizer residual to keep the warranty valid — ozone alone often isn't enough on paper, so check your manual. And cold doesn't sanitize. The organisms that cause plunge-related skin infections tolerate cold water perfectly well, and a few of the nastier ones shrug off low chlorine too. Chilled water buys you time; it doesn't disinfect.
One thing people get wrong: cold water isn't self-cleaning. The chill slows bacteria down, but body oils, sweat, lotions and skin still go in every session — and in 100 gallons they concentrate fast. Cold buys you time; it doesn't replace sanitizer, filtration, or fresh water.
Nearly every market we serve runs hard: San Diego measures roughly 216–276 ppm, and Phoenix, Austin and Central Texas, Florida, and most of Southern California are the same or harder. (Tahoe and parts of the Bay Area are the exception — genuinely soft.) Hard water means two things wherever you are: never add calcium or hardness-up products (you'd make scale worse), and your plunge benefits from a metal & scale sequestrant to keep minerals from staining the shell or clogging the chiller. We dose this on our visits — it's included in your kit if you're on a plan. Not sure about your water? Your technician tests it on the first visit.
Different shells need different care. Here's the rule for each — and what will damage it.
| Material | Clean it with | Never use |
|---|---|---|
| Acrylic Plunge, Sun Home, Chilly Goat |
Warm water + soft cloth, or a mild spa surface cleaner | Acetone, solvents, abrasive pads — they permanently craze and cloud acrylic |
| Stainless steel Renu, some BlueCube |
Chloride-free stainless cleaner, soft cloth, wipe with the grain. Follow the factory's ozone program — go light on chlorine. | Steel wool, chlorine-based cleaners, abrasives — they seed pitting corrosion |
| Rotomolded plastic ORCA, budget tubs |
Mild soap and water | Pouring sanitizer concentrate directly onto the surface |
| Cedar / wood-lined | Damp wipe, let it breathe, tannin-aware care | Harsh sanitizer soaks (wood absorbs them) and pressure washing |
Not sure what your plunge is made of? Some brands (like BlueCube) ship in stainless, carbon fiber, or acrylic. When in doubt, ask us — we'll tell you exactly what's safe for your unit.
Most premium plunges sanitize the same way — and we follow what your tub was built for.
Nearly every quality cold plunge has a built-in ozone or UV system doing continuous, chemical-free sanitation behind the scenes. On top of that, the manufacturer has you add a residual sanitizer that keeps the water and plumbing protected between sessions — and for most brands, that residual is chlorine. We use exactly what your tub was designed for:
| Your plunge | Built-in | What it's built for |
|---|---|---|
| Plunge | Ozone | Chlorine residual (Sirona Replenish — a 15% chlorine product). Supports chlorine or chlorine-free. |
| Chilly Goat | UV | Chlorine granules, held at 1–3 ppm |
| Renu Therapy | Ozone + filter | Ozone does the heavy lifting; optional chlorine-free Sirona Simply kit if you prefer no chlorine |
| Sun Home · AquaVoss · ORCA · others | Varies | We confirm your unit on-site and match it |
A quick word on "Sirona." You'll see the Sirona name on a lot of plunges — but most of what ships (like Plunge's Sirona Replenish) is actually a chlorine product, not the chlorine-free "Simply" line. We stock the right Sirona products for your tub, so you're using the same brand your manufacturer trusts.
Why chlorine for most setups? Cold water reactions run about twice as slow as a hot tub, so you need a sanitizer that leaves a continuous protective residual between sessions — chlorine does, while peroxide, UV, and ozone alone don't (biofilm can quietly grow in the plumbing). For chlorine-free tubs like Renu, the built-in ozone covers that gap. Either way, we keep it matched to your equipment so you don't have to think about it.
Cloudy water that won't clear · a musty or swampy smell · slimy walls · chlorine you can't keep up no matter what you add · anything that just feels "off." That's a service call, not a chemistry experiment. The longer biofilm sits, the bigger the job — catch it early. Text or call (619) 289-9282.
Our maintenance plans keep your water dialed in year-round — testing, balancing, filters, deep cleans, and the right chemistry delivered to your door. You just plunge.
This guide reflects The Cold Standard's general service practices for residential and light-commercial cold plunges in the markets we serve. Specific dosing depends on your water volume, usage, equipment, and source water — your technician sets the exact amounts for your unit. Commercial and public facilities carry additional regulatory requirements; see our Compliance page. Always follow the safety directions on every product label.