How to Clear Green Pool Water: Complete Algae Treatment Guide

Tools & Supplies Needed

Find on Amazon: Taylor K-2006 Test Kit , Liquid Chlorine , Muriatic Acid , Pool Brush

First, Let's Diagnose Your Green Pool Problem

Before jumping into treatment, we need to understand what we're dealing with. Green pool water is almost always caused by algae growth, but the severity and type determine your treatment approach.

Look at your pool and assess the green color intensity:

• Light green or cloudy: Early-stage algae, relatively easy to treat
• Medium green: Established algae bloom, requires more aggressive treatment
• Dark green or black-green: Severe algae infestation, may take several days to clear
• Green with visible algae clumps: Multiple algae types present, needs extended treatment

Next, check if you can see the bottom of your pool. If you can see the main drain clearly, you're dealing with light algae. If you can't see past 2-3 feet deep, you have a heavy infestation.

Essential Water Testing Before Treatment

Grab your Taylor K-2006 test kit or comparable FAS-DPD test kit and measure these crucial levels:

• Free Chlorine (FC): Likely near zero in green pools
• pH level: Often elevated above 8.0 due to algae photosynthesis
• Cyanuric Acid (CYA): Critical for determining proper shock levels
• Total Alkalinity (TA): May need adjustment after pH correction

Safety Warning: Never mix different types of pool chemicals. Always add chemicals to water, never water to chemicals, and wear protective equipment.

The SLAM Method: Your Green Pool Solution

SLAM (Shock Level And Maintain) is the most effective method for clearing green pools. Here's how to execute it properly:

Step 1: Calculate Your Shock Level

Your shock level depends entirely on your CYA reading. Use this FC/CYA relationship:

• CYA 30ppm = FC shock level 12ppm
• CYA 40ppm = FC shock level 16ppm
• CYA 50ppm = FC shock level 20ppm
• CYA 60ppm = FC shock level 24ppm
• CYA 70ppm = FC shock level 28ppm

If your CYA is above 80ppm, you'll need to partially drain and refill your pool before treatment becomes effective.

Step 2: Adjust pH First

Before adding chlorine, get your pH between 7.2-7.4 using muriatic acid. High pH makes chlorine less effective, so this step is crucial. Add acid slowly in the deep end with the pump running, then retest after 2 hours.

Step 3: Add Liquid Chlorine

Use only liquid chlorine (sodium hypochlorite) for the SLAM process. Avoid cal-hypo shock products as they'll raise your pH and calcium levels. Calculate your initial dose:

For every 10,000 gallons of water, add approximately 1 gallon of 12.5% liquid chlorine to raise FC by 5ppm. So if you need to go from 0ppm to 20ppm FC, you'll need roughly 4 gallons for a 10,000-gallon pool.

Add the chlorine around the perimeter of the pool with the pump running. Never pour all the chlorine in one spot.

Maintaining Shock Level Until Clear

Here's where many pool owners fail: you must maintain shock level continuously until the water clears completely. This means:

1. Test FC every 2-4 hours during daylight hours
2. Add more liquid chlorine whenever FC drops below shock level
3. Run your pump 24/7 during treatment
4. Clean your filter daily or backwash sand/DE filters

The algae is dying when your FC loss slows down significantly overnight (less than 1ppm loss). Continue until you can maintain shock level overnight with minimal chlorine consumption.

Filtration and Circulation Critical Points

Your filtration system works overtime during algae treatment:

• Run pumps continuously: Dead algae must be filtered out
• Clean cartridge filters daily: Rinse with garden hose, rotate multiple sets
• Backwash sand filters daily: Until backwash water runs clear
• Add DE powder after each backwash: If you have a DE filter
• Brush pool surfaces twice daily: Helps dislodge algae from surfaces

Timeline Expectations and Troubleshooting

Light green pools typically clear within 24-48 hours using proper SLAM technique. Dark green pools may take 3-7 days of consistent treatment.

If your pool isn't clearing after 48 hours:

• Verify you're maintaining true shock level: Test more frequently
• Check filter condition: Clogged filters can't remove dead algae
• Ensure proper circulation: All areas of pool should have water movement
• Consider phosphate levels: High phosphates (above 500ppb) can fuel algae regrowth

Post-Treatment Pool Maintenance

Once your pool passes the overnight chlorine loss test (OCLT) and water is crystal clear:

1. Allow FC to drop naturally to your normal operating range (based on CYA level)
2. Rebalance pH to 7.4-7.6 and TA to proper range
3. Clean and sanitize all pool equipment that contacted algae-infected water
4. Resume normal sanitation and testing schedule

Remember, green pools are preventable with consistent water testing, proper chlorine levels, and regular brushing. The SLAM method works every time when executed correctly, but patience and persistence are essential for complete algae elimination.