PooloraCloudy pool water: causes and fixes
Cloudy water almost always comes from one of four things. Test first, find which one it is, and fix that one instead of throwing products at the pool.
- Test free chlorine, pH, alkalinity, calcium and stabilizer.
- Chlorine below the minimum for your stabilizer is the most common cause: fix it first.
- If chlorine is fine, look at the filter and at water balance (CSI).
Cause 1: chlorine too low for your stabilizer
Cloudiness is often the first stage of algae or bacteria growth, before the water turns green. Compare your free chlorine with the minimum for your stabilizer:
| Stabilizer (CYA) | Minimum free chlorine |
|---|---|
| 0 ppm | 1 ppm |
| 30 ppm | 2.25 ppm |
| 40 ppm | 3 ppm |
| 50 ppm | 3.75 ppm |
| 60 ppm | 4.5 ppm |
| 80 ppm | 6 ppm |
If you are below it, raise chlorine and keep it up; if it keeps disappearing, treat it like early algae and follow the green pool steps.
Cause 2: the filter is not keeping up
- Run the pump longer, around the clock while the water is cloudy.
- Check filter pressure. Clean or backwash when it rises above its clean reading, and replace worn cartridges.
- Make sure the skimmer and pump baskets are empty and the water level is high enough for the skimmer.
Cause 3: high pH and calcium (scaling water)
When pH, alkalinity and calcium are high together, especially in warm water, calcium carbonate comes out of solution as a fine white haze. The Calcium Saturation Index (CSI) tells you if this is the case; Poolora treats −0.3 to +0.5 as balanced.
| Water at 85 °F, CYA 40 | CSI | Result |
|---|---|---|
| pH 8, TA 120, CH 400 | 0.82 | Scaling: cloudy, crusts |
| Same water at pH 7.5 | 0.35 | Balanced |
In this example, lowering pH alone brings the water back into balance. See how to lower pH.
Cause 4: the end of a shock or a storm
After algae dies or a storm washes dirt in, the water is full of fine particles. Keep chlorine at the right level and filter continuously; it usually clears as the filter catches up. Vacuum anything that settles on the floor.
Which one is it? Quick checks
| What you see | Likely cause | Check |
|---|---|---|
| Cloudy, chlorine low or dropping fast | Biology: early algae or bacteria | Free chlorine vs the minimum for your CYA |
| White haze, crusts on tile, pH 7.8 or higher | Water balance (scaling) | pH, alkalinity, calcium and CSI |
| Cloudy and filter pressure higher than usual | Dirty or clogged filter | Clean or backwash, then compare pressure |
| Cloudy and filter pressure lower than usual | Poor flow: full baskets, low water or an air leak | Baskets, water level, pump lid |
| Cloudy after rain, a party or a shock | Fine particles | Keep filtering and keep chlorine up |
How to keep it from coming back
- Keep free chlorine above the minimum for your stabilizer every day, not just after you notice a problem.
- Keep pH in 7.2–7.8 and check water balance when the weather gets hot: warm water scales more easily.
- Run the pump long enough every day for the filter to keep up, and clean the filter before pressure gets high.
- New plaster releases dust and pushes pH up during its first weeks; follow your plasterer's start-up instructions.
What to do, in order
- Test everything.
- Fix chlorine first if it is below the minimum.
- Run the pump nonstop and clean the filter.
- If CSI is above +0.5, lower pH with acid.
- Retest the next day before adding anything else.
Common questions
Should I use a clarifier or flocculant?
Only after chemistry is right. A clarifier clumps fine particles so the filter can catch them; a flocculant drops them to the floor so you can vacuum them out to waste. Neither fixes low chlorine.
Is cloudy water safe to swim in?
Not if you cannot see the main drain: it hides swimmers in trouble. Wait until the water is clear and chlorine is inside your label's swimming range.
Do it with your own products
Poolora turns your test into the exact amount of the products on your shelf, in cups and ounces, in the right order, and tells you when it's safe to swim. Free to start; every chemical, water balance and history are part of Pro.
Keep going
Sources
- CDC: Home pool and hot tub water treatment and testing
- O'Brien, J. E. et al. (1974), chlorine and cyanuric acid equilibria in water
- APSP water balance range (CSI −0.3 to +0.5) as used by Poolora
- Doses: Poolora engine (mass balance for chlorine; carbonate-equilibrium model for pH with constants from the USGS PHREEQC database)