Cloudy hot tub water? Causes and how to clear it

A hot tub turns cloudy for the same few reasons almost every time. Jacuzzi, Bullfrog and Hot Spring all list low sanitizer, a dirty filter and oils and lotions building up in the water. Jacuzzi and Bullfrog add high pH or alkalinity.

Fix them in order. Often the first three steps are enough.

Quick diagnosis

Your test results narrow it down fast.

• Sanitizer low: that's the most likely cause. Raise it and shock (steps 1 and 2).
• Sanitizer fine but pH high: lower pH first (step 1).
• Everything tests fine: the filter is the next suspect (step 3).
• Cloudy right after a refill: look at your fill water and calcium (step 4).
• Flakes or specks floating in fresh water: buildup coming out of the plumbing. Purge the lines before your next drain (step 6).

1. Test and adjust pH, alkalinity and sanitizer

Start with a test. Jacuzzi's own troubleshooting order puts this first.

High pH is a common culprit. Jacuzzi, Bullfrog and Hot Spring all target pH 7.2 to 7.8 (the CDC's range is 7.0 to 7.8). For total alkalinity, Jacuzzi and Bullfrog both say 80 to 120 ppm.

Then sanitizer. The CDC's minimum for hot tubs is 3 ppm free chlorine, or 4 to 8 ppm bromine. If you're low, the hot tub calculator gives the amount. For a 400-gallon tub, lowering pH from 8.0 to 7.6 with dry acid (sodium bisulfate, sold as spa pH decreaser) takes about 1.3 oz. Use a spa pH decreaser rather than muriatic acid, and check your manual first: Jacuzzi's says never to add acid to its tubs.

Add pH decreaser and shock separately, straight into the water with the jets running, and let the water circulate before the next one. Never mix them, or any spa chemicals, in a cup or bucket; acid and chlorine together release chlorine gas.

2. Shock

Shock breaks down the oils, lotion and other organic gunk that clouds the water. Use a chlorine or non-chlorine spa shock and follow the label.

Leave the cover open with the jets running for a while afterward so fumes can escape (Jacuzzi's manual says at least 20 minutes). Give it time before anyone gets in. Hot Spring says free chlorine above 5 ppm can irritate skin, so let it drop below 5 first.

3. Clean or replace the filter

A dirty filter is on every maker's list. Pull it, hose it off between the pleats, and soak it in filter cleaner if it's due. Rinse it very well afterward.

How often? Bullfrog and Hot Spring both say about monthly. AQUA Magazine suggests a good rinse every week and a deep clean every month or two. When to replace it varies a lot by filter (Bullfrog says about a year), so check your manual, and replace any filter with torn fabric or crushed pleats.

4. Look at calcium and fill water

Pool & Spa News notes that calcium dissolves less in hot water, so it can come out as scale or cloud the water. Caldera says fill water above 400 ppm calcium can cloud a spa, and so can iron or copper. If your tub clouds up right after every refill, have your fill water tested.

5. Clarifier, sparingly

Clarifier helps the filter catch very fine particles. Jacuzzi says to use it sparingly and to fix the root cause. It won't fix low sanitizer or a clogged filter.

6. Purge, drain and refill

Still cloudy? Change the water.

Before you drain, run a line purge through the plumbing. Pool & Spa News explains why: buildup inside the pipes can flake out into the tub, straight into your fresh water. SpaGuard System Flush is one example; its label says to add it before draining and run the pump for 15 minutes. Follow your product's directions.

Then drain, wipe down the shell, clean the filter and refill. Balance the new water before the first soak.

How often to change the water

Even without trouble, hot tub water wears out. Most land on 3 to 4 months: Caldera and AQUA Magazine say 3 to 4, and Bullfrog says about every 4 with its FROG system.

There's also a formula from the CDC, Pool & Spa News and AQUA Magazine: gallons ÷ 3 ÷ average daily users = days between water changes. A 300-gallon tub used by 3 people a day works out to about 33 days. Use whichever comes first. The hot tub care guide has more on the routine, and the test log has hot tub targets printed on it.