· by Michael Blair, Nashville's Pool & Spa
Cloudy water is fine particles suspended in the pool, and there are only a few reasons they are there. Working through them in order avoids the common cycle of adding chemicals that do not address the cause.
Test before adding anything
Free chlorine, pH, total alkalinity, calcium hardness and cyanuric acid. Cloudiness with adequate chlorine is a different problem from cloudiness with none.
High pH is the most common cause here — it reduces chlorine effectiveness and causes calcium to come out of solution, which is literally what you are seeing.
Filtration and circulation
A pool needs enough run time to turn the whole volume over, and in a Middle Tennessee summer that is longer than people run it. Under-filtering shows as persistent haze that chemicals do not clear.
Then check the filter itself — a clogged cartridge, a sand bed needing backwash, or a DE grid that needs recharging.
- Test the full panel before adding anything
- High pH is the most common local cause
- Increase run time in summer heat
- Backwash or clean the filter
- A clarifier or flocculant clears fines the filter cannot catch
Cyanuric acid lock
Stabilizer protects chlorine from sunlight and accumulates, because it is not consumed. Too much and chlorine becomes ineffective at normal levels.
The only real fix is partial draining and refilling. It is a common cause of a pool that will not hold chlorine despite constant dosing.
After heavy rain
Middle Tennessee storms dilute chemistry and wash organic material in. Cloudy water two days after a storm usually needs testing and rebalancing rather than a diagnosis.
Brushing and running the filter longer for a couple of days handles most of it.