Clear cloudy pool water by first testing chemistry levels, then shocking to proper FC/CYA ratio, running filtration 24/7, and using clarifier if needed. Most cases resolve within 24-48 hours with proper chlorine levels.
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Cloudy pool water isn't just one problem—it's a symptom with multiple possible causes. Before throwing chemicals at your pool, we need to identify what's creating the cloudiness. The most common culprits are inadequate chlorine levels, poor filtration, chemical imbalances, or algae beginning to bloom.
Start by examining your water closely. Is it a milky white cloudiness, greenish tint, or more of a dull hazy appearance? White cloudiness typically indicates filtration issues or chemical imbalances, while any green tint suggests algae growth requiring immediate SLAM treatment.
Using a reliable test kit like the Taylor K-2006C, test these critical parameters:
If your FC is below the recommended level for your CYA, this is likely your primary issue. Low chlorine allows contaminants and micro-organisms to multiply, creating cloudiness.
Before addressing chlorine, get your pH in the proper range. If pH is above 7.6, chlorine becomes less effective. Add muriatic acid to lower pH—typically 1 quart per 10,000 gallons drops pH by 0.2 points, but always follow manufacturer instructions and retest.
If TA is too high (common cause of rising pH), you'll need to lower it using muriatic acid with the aeration method. Add acid to bring pH to 7.0-7.2, then aerate until pH rises back to 7.4-7.6. Repeat this process until TA reaches target range.
Once pH is balanced, bring your FC up to the appropriate shock level based on your CYA reading. Use liquid chlorine (sodium hypochlorite) rather than granular pool shock, which often contains calcium hypochlorite that can cloud water further.
For shock levels, follow the FC/CYA relationship:
Add approximately 1 gallon of liquid chlorine per 10,000 gallons to raise FC by 1 ppm. Always add chemicals to water, never water to chemicals, and ensure proper ventilation.
Switch your pool pump to run 24/7 until water clears. Your filtration system is crucial for removing the particles causing cloudiness. Clean or backwash your filter before starting—a dirty filter can't effectively clear cloudy water.
For sand filters, backwash until water runs clear. For cartridge filters, remove and hose down thoroughly or replace if they're beyond cleaning. DE filters should be backwashed and recharged with fresh diatomaceous earth.
Test FC levels every few hours and add more liquid chlorine as needed to maintain shock level. This is the SLAM (Shock Level And Maintain) method. Don't let FC drop below shock level until your water is completely clear and you're passing the OCLT (Overnight Chlorine Loss Test).
The SLAM process typically takes 1-3 days for cloudy water, longer if algae is present. You'll know you're winning when FC levels stop dropping rapidly between doses.
If proper chemistry and filtration don't clear your pool within 48 hours, consider these additional steps:
Add a quality clarifier like SeaKlear or BioGuard Polysheen Blue to help coagulate tiny particles your filter can catch. Follow label directions—typically 1 ounce per 5,000 gallons. Run filtration continuously and clean filter frequently as it captures clumped particles.
For severe cloudiness, flocculant drops particles to the pool bottom for vacuuming to waste. Turn off circulation, add floc according to directions, let settle 8-12 hours, then vacuum directly to waste. This removes water from your pool, so be prepared to refill.
Retest water chemistry every 4-6 hours during treatment. Once water clears, perform the overnight chlorine loss test: note FC level at dusk, test again at dawn. If FC drops more than 1 ppm overnight, continue SLAM process.
After achieving crystal clear water and passing OCLT, reduce FC to normal maintenance levels for your CYA and resume regular testing schedule.
Maintain proper FC levels daily, test chemistry 2-3 times weekly, clean filters regularly, and ensure adequate circulation. Consistent maintenance prevents future cloudiness issues and keeps your pool swim-ready.
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