Cloudy water is a symptom. The usual causes are not enough sanitizer, pH or alkalinity out of range, a dirty filter, and old, overused water. Check them in that order. It’s a common troubleshooting sequence, and your manual may suggest a different one. This is general water-care guidance. Your spa’s owner’s manual wins wherever it differs.
To see whether your fill water runs hard or soft, enter your ZIP in What’s in your hot tub water?. It’s free.
Check sanitizer first
Test before you add anything. CDC’s guidance for hot tubs is free chlorine at least 3 ppm (or bromine 4–8 ppm). Don’t go past your manufacturer’s upper limit. CDC also advises against using cyanuric-acid (stabilized) chlorine products in hot tubs. If sanitizer is low, bring it back up and shock per your product label, then run the jets so it circulates. Hot Spring’s manual says to run the jet pump at least ten minutes after adding chemicals.
How to shock a hot tub covers when to shock and what to use.
Then pH and alkalinity
CDC’s range for pH is 7.0–7.8. Balance total alkalinity (TA) first, because it buffers pH. Hot Spring gives 40–120 ppm TA. Hot Spring also notes that pH above 7.8 can lead to cloudy water and scale. More on this in why hot tub pH keeps rising and how to lower alkalinity.
Then the filter
A dirty cartridge can’t trap the fine particles, oils and lotions that cloud the water. Hot Spring recommends rinsing filters monthly and using a filter cleaner for oils and buildup. Replace cartridges on the schedule in your manual. If you also have suds, see hot tub foam fixes.
Hard fill water and scaling
High calcium together with high TA and pH can scale and cloud the water. Spa manuals differ: Hot Spring’s Hot Spot manual gives 50–150 ppm for calcium hardness, and another maker’s manual gives 75–150 ppm; check yours. If your fill water is hard, Water Match shows your ZIP’s water profile so you know before you refill.
How to raise calcium hardness covers low calcium.
When to drain and refill
Drain and refill when the water still won’t clear after sanitizer, balance and the filter are all right, or when your manual’s interval is up. “Overused or old water” is on the maker’s own list of causes. If scale has formed, Hot Spring says to drain, scrub it off, refill and rebalance. Balance the water every time you refill.
Check your water, then join the free founding list
Enter your ZIP to see whether your fill water is Soft, Balanced, or Hard. After your result, you can join the free founding list for Cycle Box, which isn’t on sale yet.