Why Is My Pool Cloudy? 6 Causes and How to Clear It Fast
Cloudy pool water comes from low chlorine, a struggling filter, or water chemistry out of balance. Find your cause in a few minutes and clear it the right way.
Cloudy water means something tiny is floating in the pool that the filter isn’t catching or the chlorine isn’t killing. It’s rarely dangerous on its own, but it’s an early warning: cloudy today is often green next week.
Here are the six causes, in the order to check them.
1. Chlorine is too low
The most common cause. Bacteria and early algae cloud the water before it turns green. Test free chlorine and stabilizer (CYA): if chlorine is below about 7.5% of your CYA, raise it. The pool chemical calculator gives the dose for your pool. If the water has a green tint too, follow the green pool fix instead.
2. The filter isn’t keeping up
A dirty filter, a pump that runs too few hours, or the wrong valve setting all leave particles in the water.
- Sand filter: backwash when pressure is 8–10 psi above clean.
- Cartridge: hose it off; replace it if it’s torn or years old.
- DE: backwash and recharge with fresh DE.
Then check run time: the pump should move all the water at least once a day. The pool pump calculator shows how many hours that takes with your pump.
3. pH and alkalinity are high
At high pH (above 7.8), calcium comes out of solution as fine white particles. That gives a milky look, and chlorine works poorly too. Lower pH with muriatic acid or dry acid in small steps. See how to lower pH.
4. Calcium hardness is too high
Very hard water plus high pH clouds easily and leaves white scale at the waterline. Keep pH at the lower end (7.2–7.4). If hardness is far above 400–500 ppm, the only real fix is replacing part of the water.
5. Right after shocking or a storm
Dead algae, pollen and dust from a storm take a day or two to filter out. Keep the pump running and clean the filter once or twice. That’s all.
6. Too much stabilizer
High CYA doesn’t cloud water directly, but it makes your normal chlorine level too weak, so the water keeps clouding no matter how much you add. Above about 80–100 ppm in a chlorine pool, replace some water. The pool fill cost calculator tells you what the water costs.
Clarifier or flocculant?
- Clarifier clumps fine particles so a sand or cartridge filter can catch them. Use it for slight to moderate haze, with the pump running.
- Flocculant sinks everything to the floor overnight with the pump off. Then you vacuum to waste. It is faster for very cloudy water, but you lose water and must have a waste setting.
Neither one fixes chemistry. Get chlorine and pH right first or the cloudiness comes back.
Run the numbers for your pool
Using your saved pool: . My pool
4 chemicals to add
Add them one at a time, a few hours apart, with the pump running. Never mix chemicals together.
- Pool size
- 15,000 gal
- Chlorine target
- 4 ppm
- Stabilizer target
- 40 ppm
What to add
- 6.3 lbBaking soda (sodium bicarbonate) to raise alkalinity by 30 ppm
- 18 lbCalcium chloride (dihydrate, 77–80%) to raise hardness by 100 ppm
- 2.5 lbStabilizer (cyanuric acid) to raise CYA by 20 ppm. Dissolves slowly: use a sock in the skimmer
- 57.6 fl ozLiquid chlorine 10% to raise free chlorine by 3 ppm
What would change your result
Read every product label and follow its safety directions.
Quick answers
Why is my pool cloudy after shocking?
Often it's normal: shock kills algae and bacteria, and the dead particles are too small for the filter at first. Keep the pump running and clean the filter. Cal-hypo shock can also cloud water briefly when it raises calcium in water with high pH.
How do I clear a cloudy pool fast?
Fix the chemistry first (chlorine up, pH 7.2–7.6), run the pump around the clock and clean the filter. A clarifier helps a sand or cartridge filter catch fine particles; a flocculant drops them to the floor to vacuum to waste.
Does too much chlorine make a pool cloudy?
Liquid chlorine itself doesn't. Granular shock can leave a temporary haze while it dissolves, and cal-hypo can cloud high-pH, high-calcium water.
How long does it take for a cloudy pool to clear?
With good chemistry and a clean filter, one to three days for a mildly cloudy pool. If it hasn't improved after three days, look again at the filter.
Pool costs in your state
What a pool pump and a hot tub cost to run at your state's electricity price.
Keep reading
How to Raise pH in a Pool: Soda Ash, Aeration or BoraxLow pool pH stings eyes and eats equipment. Here's how to raise it with aeration, soda ash or borax, how much to start with, and why it keeps dropping.
Pool Green but Chlorine Is High? 4 Real Causes and FixesA green pool with a high chlorine reading usually means metals, too much stabilizer, a misleading test or pollen. Here's how to tell which one you have and what to do.
Pool Salt Cell Guide: How It Works, Cleaning and Low Salt ReadingsHow a pool salt cell makes chlorine, how to clean it, how long it lasts, and why it reads 'low salt' when the water isn't. A practical guide for salt pool owners.