Cleaning & Descaling Your Cold PlungeUpdated 40 minutes ago

Cold Plunge Water Maintenance covers how often to change your water. This guide covers everything else: cleaning the tub, removing mineral scale, keeping your chiller’s water loop clear, and the products that are safe to use.

Step 1: Work out what you’re dealing with

Hard water areas: if your kettle or shower head builds up white scale, expect your plunge to as well. Check the filter housing and hose fittings every time you change the water.

Step 2: What’s safe to use

Never use

• Household bleach. It damages tub materials, seals and chiller components.
• Calcium hypochlorite (unstabilised chlorine or “pool shock”).
• Strong acids: hydrochloric (muriatic) or sulfamic acid products, including many toilet and tile descalers.
• Abrasive cleaners, scourers, steel wool or solvent-based products.
• Pressure washers. They damage inflatable PVC, seams and valves.
• Mixing chemicals. Never combine acid with bleach or chlorine. It releases toxic chlorine gas. Never mix two different sanitiser systems either. Pick one and stick with it.

Using chlorine? It isn’t our recommended sanitiser for chiller systems because of the risk of corrosion. If you choose to use a stabilised chlorine such as dichlor:

• keep free chlorine between 1.0 and 2.0 ppm. Above 3 ppm significantly increases corrosion risk to the chiller’s heat exchanger.
• keep pH between 7.2 and 7.6
• test your water at least weekly
• change your water regularly, as dichlor gradually builds up cyanuric acid, which increases corrosion risk over time
• don’t use it as a long-term, everyday treatment.

After adding any treatment: let the chiller circulate for at least 30 minutes before you get in. Do not enter directly into a freshly treated water system.

Step 3: Deep clean your tub (every water change)

1. Turn off and unplug the chiller.
2. Drain the tub. Open the drain valve at the base and direct the water to a suitable drain. To drain faster, disconnect the chiller outlet hose and use it to direct the flow.
3. Wipe all interior surfaces and the waterline with mild soap and a soft cloth. Pay attention to the floor and corners, where biofilm settles first.
4. Remove scale if you have any. Wipe or soak the affected areas with a citric acid solution (about 30–50 g per litre of lukewarm water). Leave it for 10–15 minutes, wipe it away, then rinse thoroughly.
5. Clean the fittings. Hose connectors and brass inserts can scale up in hard water areas. Soak them in the same citric solution, rinse, and check that the O-rings are in place before refitting.
6. Rinse everything with fresh water, and drain the rinse water.
7. Check your filters and clean or replace them as needed.
8. Refill, restart circulation, and add your water treatment.

Care by tub type

Step 4: Descale your chiller

A chiller’s water loop runs cold, so heavy scale is uncommon. In hard water areas, though, deposits can build up in the fittings and filter housing over time.

When to descale

• You can see white or crusty deposits on the filter housing, hose fittings or filters, or
• Water flow has dropped even though your filters are clean.

Otherwise, a quick check every 3 months is enough for most homes. If the problem is cloudy water or a blocked filter, descaling won’t help. You need to swap out your water.

You’ll need: 

• Citric acid
• A clean bucket
• Gloves and eye protection
• Fresh replacement filters.
• Mix about 30–50 g of citric acid per litre of lukewarm water (under 104°F / 40°C).

Steps

1. Power off and unplug. Drain the tub and the chiller loop.
2. Remove all filters (the cartridge, paper filter and mesh). The acid will damage them, and you’ll fit fresh ones afterwards.
3. Set up a closed loop. Run the chiller’s inlet and outlet hoses into a clean bucket, or into the empty tub, with just enough solution to keep the inlet covered. Keep the solution level above the chiller so the pump never runs dry.
4. Circulate for 30–60 minutes with the compressor off. Set the target temperature above the room temperature so the unit doesn’t cool. If your pump doesn’t circulate in this mode, let the solution soak in the loop for the same time instead.
5. Drain the solution and dispose of it down a household drain with plenty of running water.
6. Flush with clean water at least twice, circulating for 10–15 minutes each time, until the rinse water runs clear with no smell. A pH strip reading close to your tap water confirms it’s done.
7. Reassemble. Check that every O-ring and washer is present and sitting flat, then fit fresh filters.
8. Refill and purge the air. With the unit off, let water fill the filter housing until it overflows. This removes trapped air. Skipping it can trigger an E2/Water flow alarm.
9. Run for 15–30 minutes and check for leaks at the hose connections and filter housing.

Not confident doing this yourself? Contact us, and we’ll walk you through it.

Step 5: Keep it clean between water changes

• Shower before you plunge. It’s the single biggest thing you can do to keep water cleaner for longer.
• Keep the lid on when you’re not using it.
• Let the ozone and filtration run as recommended. They extend water life, but they don’t replace cleaning, sanitising or water changes.
• Add your oxidiser or sanitiser weekly, or after heavy use.
• Test your water weekly if you use chemical treatment. Aim for pH 7.2–7.6.
• If it looks, smells or feels off, change it. Don’t try to fix bad water with more chemicals.

Using heating mode?

Warm water grows bacteria much faster than cold water. If you use your chiller’s heating mode:

• Change the water more often than the cold-use schedule
• Drain, clean and refill when switching back from regular warm use to cold
• Check that your sanitiser works at higher temperatures. Some, like hydrogen peroxide, are less effective in warm water.