Cloudy hot tub water: causes and fixes

Common symptoms

• The water looks hazy or milky, and you cannot see the seats or the floor clearly.
• It turned cloudy after a party or a busy weekend.
• It went cloudy soon after a refill.
• Rough white crust or flakes show up on the shell along with the haze.
• The water smells musty, or the walls feel slimy.
• Foam sits on top when the jets run.

Quick checks before anything else

• Test free chlorine or bromine, pH and total alkalinity with in-date strips.
• Pull the filter cartridge. Gray, brown or greasy pleats mean it needs cleaning.
• Check the water level and run the jets. Weak flow means less water gets filtered.
• Test calcium hardness, especially if you see white crust.
• Count the weeks since the last drain and refill.
• Note whether the haze came on after heavy use, a refill, or a new chemical.

Why is my hot tub water cloudy?

Hot Spring’s troubleshooting chart lists five causes of cloudy spa water, and its water section adds two more. Most cloudy tubs have more than one at once.

• Low sanitizer Not enough chlorine or bromine to keep up with bathers, so tiny particles and germs build up. Often comes with a musty smell.
• Dirty filter A clogged cartridge lets fine particles stay in the water. Jets may also feel weaker.
• Body oils and organic matter Sweat, skin oils and lotions cloud the water after heavy use, often with a scum line.
• High pH Hot Spring says pH above 7.8 can cloud the water and form scale on the shell and heater.
• High calcium hardness Hot Spring says high calcium can cause cloudy water and scaling. Common with hard or well water.
• Old water Water that has been in the tub too long. It stays dull even when every reading is in range.

Step-by-step: how to clear cloudy hot tub water

We fix the cheap things first: the readings, then the filter, then a shock. Only when the water stays cloudy after all of that is a drain and refill the answer.

1. Test before you add anything. The CDC says hot tub water needs at least 3 ppm (parts per million) of free chlorine, or 4 to 8 ppm of bromine, and a pH of 7.0 to 7.8. If a chlorine pad shows no color at all, check the strip date. Lay-Z-Spa notes that chlorine above 15 ppm can bleach the pad, so wait and test again.
2. Raise the sanitizer. If free chlorine is under 3 ppm or bromine under 4 ppm, add your sanitizer as the label and your manual direct. Hot Spring adds chemicals into the filter area with the jets on high. Hot Spring recommends keeping free chlorine at 3 to 5 ppm in its spas. Our hot tub chemical calculator works out the amount for your tub’s size.
3. Check calcium hardness. Hot Spring balances calcium first, then alkalinity, then pH. It lists 75 to 150 ppm for its spas, and Intex lists 150 to 250 ppm for its inflatable spas. If calcium is well above your manual’s range and you see white crust, use a calcium remover made for spas, per its label, or replace part of the water with softer water. Hot Spring suggests an in-line pre-filter on the fill hose to catch metals and dirt.
4. Balance alkalinity, then pH. Total alkalinity is the water’s buffer that holds pH steady, so set it before pH. Hot Spring says a high pH neutralizes the sanitizer, promotes scale and clouds the water. Use pH decreaser if pH is above your manual’s range, a little at a time, and retest after the jets have run.
5. Clean or replace the filter. Hot Spring says to clean cartridges monthly and to soak them in a filter degreaser to remove oil and minerals, then hose them off. Intex says to inspect and clean its cartridges every day to once a week, and warns that a dirty cartridge can restrict flow and cause its E90 code; look up any code in our error code finder. Replace a cartridge that stays discolored after cleaning.
6. Shock with the cover open. Shock is a large dose of chlorine or a non-chlorine oxidizer (MPS) that burns off body waste and chloramines. Hot Spring says raising chlorine to 5 ppm for 24 to 48 hours clears excess waste, and to leave the cover open at least 20 minutes after a shock so the gas can vent. Stay out until free chlorine falls below 5 ppm.
7. Run the jets and let the filter work. Hot Spring’s chart lists running the jet pump and cleaning the filter for suspended particles. Lay-Z-Spa says to leave the water at least 24 hours after a shock, then test again. If the jets are weak, fix the flow first with our weak hot tub jets guide.
8. Try a clarifier only if your manual allows it. A clarifier makes tiny particles clump together so the filter can catch them. Lay-Z-Spa suggests one if the water is still cloudy after a shock, followed by a thorough filter clean. Hot Spring says not to use a clarifier with its silver ion system, because it makes the water cloudy. Dose per the label.
9. Drain and refill if it stays cloudy. Intex says to change the water when it stays cloudy even with proper chemistry. Turn off power at the breaker before you drain, and scrub the shell while it is empty, as the CDC advises. Hot Spring says to refill through the filter area with water between 50 and 70 F, so cold fill water does not trip the heater’s high limit.

Hard-shell vs inflatable hot tubs: what changes?

The cause list is the same, but the makers set different targets and schedules. Check your own manual first.

Where a manual allows 2 ppm chlorine, we still aim for the CDC minimum of 3 ppm. Small inflatable tubs change faster, so test them more often.

If foam is part of the problem, read our hot tub foam guide. For every water number in one place, see our hot tub water problems guide.

When to call a pool or spa pro

• The water is still cloudy after a drain, refill, new cartridge and in-range readings.
• The pump does not run filter cycles, or the panel shows a flow or heater message.
• Green or brown stains appear, which can mean metals in your fill water.
• Anyone gets a rash or feels sick after soaking. Stop using the tub until it is cleaned and tested.

Common questions