Cloudy pool water results from poor filtration, chemical imbalance, or contaminants. Fix by testing chemistry, shocking to proper FC/CYA ratio, and running filtration 24/7 until clear.
Cloudy pool water is one of the most common and frustrating pool problems, but it's completely fixable with the right approach. The cloudiness indicates suspended particles in your water that are too small for your filter to catch or chemical imbalances preventing proper sanitation.
The most effective solution follows this order: test your water chemistry, shock to proper FC/CYA levels using liquid chlorine, and run your filtration system 24/7 until clear. Most cases clear within 24-48 hours when handled correctly.
The most common cause of cloudy water is improper water chemistry. When your sanitizer levels are insufficient for your stabilizer level, contaminants multiply faster than they're being killed. This creates a microscopic soup of bacteria, algae spores, and organic matter.
Free Chlorine (FC) to Cyanuric Acid (CYA) Ratio: Your FC must be adequate for your CYA level. With CYA at 30ppm, you need minimum 1.5ppm FC. At 50ppm CYA, you need 2.5ppm FC minimum. Use the FC/CYA chart to determine your minimum levels.
pH Problems: pH levels outside 7.4-7.6 reduce chlorine effectiveness dramatically. High pH (above 7.8) makes chlorine nearly useless, while low pH (below 7.0) causes rapid chlorine loss and equipment damage.
Total Alkalinity (TA) Issues: Improper alkalinity levels cause pH instability, leading to constant chemistry swings that prevent effective sanitation.
Pool filtration system failures are a major cause of persistent cloudiness. Your filter must run long enough and work efficiently to remove contaminants.
Inadequate Runtime: Most pools need 8-12 hours of daily filtration, but cloudy water requires 24/7 operation until clear. Many pool owners run their systems too briefly, never achieving proper turnover.
Dirty or Worn Filter Media: Cartridge filters last 1-2 years, sand filters 5-7 years, but they need regular maintenance. Dirty filters can't remove particles effectively and may actually redistribute contaminants.
Poor Filter Sizing: Undersized filters can't handle the pool's volume adequately, especially during heavy use or after storms.
Sometimes your system is simply overwhelmed by the sheer volume of contaminants introduced to your pool.
Bather Load: Heavy swimming activity introduces oils, lotions, sweat, and organic matter faster than standard sanitation can handle.
Environmental Factors: Rain, wind-blown debris, pollen, and dust can quickly overwhelm marginal water chemistry.
Algae Growth: While cloudy water doesn't always mean algae, early algae growth often causes cloudiness before visible green color appears.
Use a quality test kit (Taylor K-2006 or TF-100) to get accurate readings. Pool test strips are notoriously inaccurate for troubleshooting.
Essential Tests:
Address chemistry problems in the correct order to avoid constantly fighting chemical interactions.
Order of Operations:
The most critical step in clearing cloudy water is proper shocking. This isn't about adding a bag of shock - it's about achieving and maintaining the right FC level for your CYA.
Use Liquid Chlorine Only: For clearing cloudy water, use sodium hypochlorite (liquid chlorine). Avoid dichlor or trichlor products as they add CYA, making the problem worse.
Calculate Your Shock Level: Your shock level depends on your CYA reading:
SLAM (Shock Level And Maintain) is the proven method for clearing problem water. This involves maintaining shock-level FC 24/7 until your pool passes specific tests.
SLAM Requirements:
OCLT Success Criteria: Your pool passes when FC drops less than 1ppm overnight with no CC present.
Run your filter continuously during the clearing process. This isn't the time to worry about electricity costs - stopping filtration will significantly extend clearing time.
Filter Maintenance During SLAM:
If you've followed the proper chemistry and SLAM process for 3-4 days without improvement, you likely have a mechanical or environmental issue.
Filter System Problems:
Hidden Contamination Sources:
Microscopic Analysis: Sometimes professional water analysis can identify specific contaminants that require targeted treatment.
System Flow Testing: Verify your pump is moving the rated volume of water and all return outlets have adequate flow.
Comprehensive Equipment Inspection: Check for cracks in filter housings, loose fittings, or worn seals that compromise filtration.
Regular shocking schedules prevent problems before they start. Most pools benefit from weekly shocking during swimming season, with increased frequency during heavy use.
Weekly Chemistry Routine:
Variable speed pumps allow you to run filtration longer at lower speeds, providing better water quality while managing electricity costs.
Seasonal Adjustments:
Preventive maintenance is far easier and cheaper than emergency repairs during swimming season.
Monthly Tasks:
Seasonal Tasks:
Some cloudy water problems require professional diagnosis and repair that's beyond typical homeowner capabilities.
Equipment Failures:
Structural Issues:
If you've properly executed SLAM for a week without success, professional help can identify issues you might miss.
Advanced Diagnostics:
Salt water pools still require proper chemistry management and can develop cloudiness just like traditional chlorine pools.
SWG-Specific Issues:
Spa chemistry requires different approaches due to higher temperatures and lower water volumes.
Spa-Specific Factors:
Most cloudy water clears within 24-48 hours when proper chemistry and filtration are applied. Severe cases may take 3-7 days of continuous SLAM treatment. The key is maintaining shock-level FC and running filtration 24/7.
No, you should not swim in cloudy pool water. Cloudiness indicates inadequate sanitation, meaning harmful bacteria and other contaminants may be present. Wait until water is crystal clear and chemistry is balanced.
Draining is rarely necessary for cloudy water and should be a last resort. Proper chemistry and filtration can clear almost any contamination. Draining is expensive, wasteful, and can cause structural problems in some pool types.
Some temporary cloudiness is normal after adding certain chemicals, especially calcium-based products. This usually clears within a few hours of circulation. Wait for proper circulation before vacuuming.
Clarifiers can help after you've corrected the underlying chemistry problems, but they won't fix poor sanitation or filtration issues. Use clarifiers as a final polishing step, not a primary treatment.
Filter cleaning frequency depends on contamination levels. During normal operation, cartridge filters need cleaning every 2-4 weeks. During cloudy water treatment, clean every 24-48 hours.
For comprehensive pool care, explore these essential maintenance topics:
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