Applies to: In-ground and above-ground home pools with sand, cartridge or DE filters, using chlorine (including salt systems). Follow your own test kit, product labels and equipment manuals.
Quick answer
Kern County Public Health's maintenance sheet for public pools and spas lists algae, poor recirculation or filtration, off chemistry (pH and disinfectant), and calcium coming out of solution as causes of cloudy water. Test first, then check circulation and the filter. CDC advises making sure you can see the drain at the bottom of the deep end before anyone gets in.[1][2]
Keep everyone out until you can see the drain
Clear water is part of supervision. CDC notes that kids can drown in seconds and in silence and recommends continuous, close supervision. Zodiac's pool-care page ties filtered water to being able to see the steps, the depth and any obstacles.[2][3][4]
In its advice for oceans, lakes and rivers, CDC also notes that cloudy water can be a warning that there are more germs in the water than normal.[2]
For the safety side in more depth, read Is It Safe to Swim in Cloudy Pool Water?
Common causes
Kern County Public Health's maintenance sheet, written for public pools and spas, describes cloudy water as water that looks murky or cloudy, and lists these causes:[1]
- Algae. See our pool algae guide if you also see green tint or spots.[1]
- Inefficient recirculation or filtration.[1]
- Improper chemistry, meaning pH and disinfectant levels. The same sheet notes that high pH can turn pool water cloudy.[1]
- Calcium particles coming out of solution.[1]
Sanitizer gets used up. CDC says pee, poop, sweat, dirt and sunlight all reduce chlorine levels, and that chlorine mixing with that dirt and waste leaves less available to kill germs.[3][5]
Step 1: Test the water
- Test chlorine and pH. CDC recommends testing at least twice a day, and more often when lots of people use the pool.[5]
- Use your kit exactly as directed. CDC says test strips are less accurate than a DPD test kit, and that owners should always follow the test maker's directions.[5]
- Kern County's sheet adds two habits: test out of direct sunlight, and use fresh reagents for accurate results.[1]
- Compare with CDC: pH 7.0 to 7.8 and at least 1 ppm chlorine in pools, or at least 2 ppm if you use cyanuric acid (stabilizer) or stabilized chlorine products.[5]
pH matters for clarity and germ control. CDC says that as pH goes up, chlorine kills germs less effectively, especially above 8.0. Kern County's sheet also lists checking overall water balance.[1][5]
Step 2: Correct sanitizer and pH, by the label
Bring sanitizer and pH back into range by following every label direction for your pool's volume. CDC says to read and follow all directions on product labels.[3]
If you shock the pool, Hayward says to follow the manufacturer's directions. It describes shock treatment as cleansing the water of algae, bacteria, dirt and other organic matter.[6]
Zodiac describes a clarifier as helping filtration by clumping fine suspended particles. If you use one, follow its label.[4]
Step 3: Check circulation and filtration
Hayward says the circulation system (skimmer, pump, pump strainer, drains and filter) helps chemicals work and keeps water filtered, and advises running the pump long enough each day to filter the water properly. Your pump's manual and settings determine what that means for your pool.[6]
- Turn the pump off at its power source, then empty the skimmer and pump strainer baskets.[6][9][10]
- Clean and maintain the filter according to its manufacturer's directions, whether sand, cartridge or DE.[6]
- Brush and vacuum to lift settled algae and sediment out of the pool.[6]
- Kern County's sheet lists inspecting recirculation equipment for proper size and operation.[1]
When to call a professional
Common questions
- Is it safe to swim in cloudy pool water?
- Not if you can't see the bottom. CDC advises checking that you can see the drain at the bottom of the deep end before getting in.[2]
- Can high pH make water cloudy?
- Kern County Public Health says high pH can turn pool water cloudy, and CDC says chlorine kills germs less effectively as pH rises.[1][5]
- Are test strips good enough?
- CDC says strips can be used but are less accurate than a DPD test kit. Whatever you use, follow the maker's directions.[5]
Sources
Official sources, checked October 13, 2026. Manufacturer instructions apply to the product named; follow the manual and label for your own equipment and products.
- Kern County Public Health (California): Public Pool and Spa Maintenance Information (kernpublichealth.com)
- CDC: Preventing Swimming-related Illnesses and Injuries (steps before and during swimming) (cdc.gov)
- CDC: Guidelines for Keeping Your Pool Safe and Healthy (May 29, 2025) (cdc.gov)
- Zodiac Pool Care: My Pool Water is Turning Green (zodiac-poolcare.com)
- CDC: Home Pool and Hot Tub Water Treatment and Testing (May 10, 2024) (cdc.gov)
- Hayward: Weekly Pool Maintenance (hayward.com)
- CDC: Use Chemicals Safely (poster) (cdc.gov)
- CDC: Store Chemicals Safely (poster) (cdc.gov)
- Hayward: Hayward Super Pump Series Owner's Manual (commerce.hayward-pool-assets.com)
- Hayward: AquaNaut suction cleaner troubleshooting guide (hayward.com)
- Zodiac/Fluidra (Polaris): Polaris 280 pressure-side cleaner manual (EN, 2018) (dam.fluidra.com)
- HRSA, U.S. Department of Health & Human Services: Poison Help (home) (poisonhelp.hrsa.gov)
Related pool care guides
Water safety for your family
Need supplies or a service visit?
Find pool stores that sell supplies and test water, or pool service companies that maintain and repair home pools.
Spot something out of date?
If a detail here no longer matches the official source, email [email protected] with the page and a link to the official source, or use our contact page. Businesses can send corrections the same way.