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Help! My Pool is Green

This tends to be the most common problem for Pool owners and is caused by the dreaded Algae. The two causes are;

  • Normal Chlorine level has dropped too low
  • Weather – thunderstorms can turn a Pool overnight

Green Algae is the most common Algae and grows on your Swimming Pool and Spa/Hot Tub surfaces. If you think your Pool or Spa/Hot Tub is turning green, run your hands across the surfaces. If it feels slimy, then you have Algae growing.

Green Algae can also manifest as a cloudy pool to begin with before turning Green, if you have a cloudy pool, always check the pH and Chlorine.

It typically appears on the steps of your Pool or in corners in small patches, the places that circulation is limited. In the right conditions, Algae can go from a small amount to a very large amount overnight, leaving your Pool looking like a swamp!

Common prevention techniques for Algae include;

  • Maintaining a Chlorine level of 2 – 4 ppm
  • Brushing at least once a week to keep it clean
  • Run your Filter for at least 8 hours a night in a 24hr period
  • Reduce the amount of Phosphates
  • Keeping Pool water below 80 degrees

To kill the Algae, you need to ‘Shock’ treat the Pool using Liquid Chlorine (Sodium Hypochlorite).

What to do

Backwash and rinse the system to enable the system to work at its optimum.

Check the Chlorine level. If the Chlorine is low, add Stabilised Chlorine Granules dissolved in warm water. This is to bring your Free Chlorine up to the correct reading as after 48 hrs, the Liquid will be burnt off leaving you with your free Chlorine level.

Add Liquid Chlorine to the Pool. This is best done at the end of the day when there is less sunlight, so the Chlorine has longer to work before UV Rays start burning it off. The amount of Chlorine depends on the size of your Pool and the amount of Algae that you have.

Brush the Algae from the walls and bottom so that it’s all floating free. This enables the ‘Shock’ treatment to attack from all sides, greatly reducing the time it takes to kill the Algae.

For 48 hours, leave the pool running on continuous. No Swimming and ideally cover off.

After 48hrs, if there is any element of green (not cloudy), repeat the process immediately.

Pool Water will be cloudy (not green) this is the dead Algae. You will now need to use a Water Clarifier to clear the fine particles that are too fine for the Filter to catch. This can be done by adding a Gel Block to the Pump Basket, alternatively you can Floc to the pool. Both of these options are a coagulant, they bind the fine bits of debris together so that (if using a Gel Block) the Filter Catches it. If Flocking the Pool, you will raise the water level, sprinkle on Floc and circulate for a couple of hours, then turn off overnight. In the morning there will be a film over the floor, this then needs to be vacuumed to waste. This will lower the water level but avoids putting the fine debris through the Filter.