How to Shock Your Pool: Complete Step-by-Step Guide

Tools & Supplies Needed

Find on Amazon: Taylor K-2006C Pool Test Kit , Liquid Pool Chlorine , Pool Chemical Safety Kit

Quick Answer

Pool shocking involves temporarily raising your free chlorine (FC) to shock level - typically 10-12 times your cyanuric acid (CYA) level. Use liquid chlorine for best results, add it in the evening with the pump running, and maintain shock level until the pool clears completely.

Step-by-Step Pool Shocking Process

1. Test Your Pool Water First
   Use a reliable test kit like the Taylor K-2006C to measure free chlorine (FC), combined chlorine (CC), pH, total alkalinity (TA), and cyanuric acid (CYA). Record all readings as they'll determine your shock dosage.
2. Calculate Your Shock Level Target
   Multiply your CYA reading by 10-12 to find your shock level. For example, if CYA is 40 ppm, your shock level should be 40-48 ppm FC. This is based on the proven SLAM (Shock Level And Maintain) method from Trouble Free Pool.
3. Determine Chlorine Dosage Needed
   Calculate how much liquid chlorine you need: each gallon of 10% liquid chlorine raises FC by approximately 1.3 ppm per 10,000 gallons of pool water. If you need to raise FC from 2 ppm to 40 ppm (38 ppm increase), you'll need about 29 gallons for a 10,000-gallon pool.
4. Adjust pH Before Shocking
   Ensure pH is between 7.2-7.6 before adding chlorine. High pH reduces chlorine effectiveness. Add muriatic acid if pH is above 7.6, following manufacturer's instructions for dosage.
5. Add Liquid Chlorine in Evening
   Start shocking after sunset to prevent UV degradation of chlorine. Pour liquid chlorine slowly around the pool perimeter with the pump running. Never add all chlorine in one spot, as this can damage pool surfaces.
6. Circulate Water Continuously
   Run your pool pump continuously during the shocking process. This ensures proper mixing and distribution of chlorine throughout the pool. Plan to run the pump for at least 8 hours minimum.
7. Brush Pool Surfaces
   While the pump runs, brush all pool surfaces including walls, steps, and behind ladders. This helps dislodge contaminants and ensures chlorine reaches all areas where algae or bacteria might hide.
8. Test FC Levels Every Few Hours
   Retest free chlorine levels 2-3 hours after adding chlorine, then again in the morning. If FC has dropped significantly overnight, add more liquid chlorine to maintain shock level.
9. Maintain Shock Level Until Clear
   Continue maintaining shock level FC until the pool water is crystal clear and FC loss overnight is less than 1 ppm. This indicates all contaminants have been eliminated.
10. Return to Normal Chlorine Levels
    Once shocking is complete, allow FC to naturally drop to normal levels (1-3 ppm for CYA 30-50 ppm). Resume regular chlorination schedule.

Choosing the Right Shock Product

Liquid chlorine (sodium hypochlorite) is the gold standard for pool shocking. It's pure, dissolves instantly, and doesn't add unwanted chemicals. Avoid calcium hypochlorite (cal-hypo) powder shock, which adds calcium and can cloud water. Dichlor shock adds CYA with each use, eventually making your pool difficult to maintain.

When to Shock Your Pool

Shock your pool when combined chlorine (chloramines) exceeds 0.5 ppm, after heavy pool use, following rainstorms, or when water appears cloudy or has strong chlorine odor. Weekly shocking isn't necessary if you maintain proper FC levels daily.

Safety Considerations

Never mix different pool chemicals and always add chemicals to water, not water to chemicals. Store liquid chlorine in cool, shaded areas and use within 2-3 months of purchase for maximum potency. Wear safety goggles and gloves when handling pool chemicals.

Troubleshooting Common Shocking Issues

If your pool remains cloudy after shocking, you may not have reached true shock level or didn't maintain it long enough. Green pools require the full SLAM process, which can take several days of maintaining shock level FC. Cloudy water during shocking is normal - continue the process until water clears completely.

Remember that shocking is a process, not a one-time chemical addition. Patience and consistent testing are key to successful pool shocking and achieving crystal clear, sanitized water.