Select Your Country


Select Your Language


How to fix a Green Swimming Pool

If you open and close your pool each year, then you may know what it’s like to open up in the spring and find a green swimming pool. Perhaps, you went on vacation and came home to a pond instead of a pool. No matter how your pool got this way, it needs to be! What’s the point of owning a pool if it looks like your lawn?

Algae, the small micro-organism that grows rapidly in warm water, is most likely the cause of your green water. But fear not! Pool algae is very easy to kill and control.

How to Fix a Green Swimming Pool

Getting Rid of Algae with Chlorine Shock

Chlorine is a very effective sanitizer for water. When you maintain a swimming pool with 3ppm (parts per million) of chlorine, it will inhibit algae from growing. However, if you let the chlorine drop, even for a day, you might be left with an algae outbreak, which can turn your water green.

The good news is, chlorine can also destroy algae; you just need to boost the levels. The fastest way is to use chlorine pool shock with a main active ingredient of calcium hypochlorite.

How to Shock Your Swimming Pool

To properly and effectively shock your pool, you will need to wait till dusk or night time to do it. Since the chlorine in the shock is unstabilized, the sun will burn it off much faster than regular stabilized chlorine. Shocking during the day will not be as effective.

Always pre-dissolve shock in water before adding to your pool. This ensures that the shock will be properly distributed throughout the water and reduce the risk of bleaching your liner, if you have one.

One pound of shock treats up to 10,000 gallons of pool water and each bag should be pre-dissolved in its own 5 gallon bucket of water (warm water works better to dissolve). Remember to always fill the bucket of water first and then add the shock. Also, keep the pool filter and pump running for at least 10 hours during and after you shock.

There is a simple formula you’ll need to follow in order to kill the algae effectively. First, you need to determine how much algae is in your water and you can tell by the color.

How To Kill Pool Algae

Light Green or Teal Pool Water

This means there’s a low amount of algae in your water and you won’t have to use a hefty amount of chlorine shock. In this case, you should double shock your swimming pool water.

To double shock, you will need to add 2 pounds for every 10,000 gallons of water. For instance, if you pool is 20,000 gallons, you will add 4 pounds of shock. Each pound pre-dissolved in a 5 gallon bucket of water and added directly to the pool at night.

Green or Dark Green Pool Water

This means there’s a medium amount of algae in your water and you’ll need to triple shock your pool. Triple shocking requires 3 pounds for every 10,000 gallons of pool water.

Black Green Pool Water

This is the worst of the worst. I like to refer to this as The Creature From The Black Lagoon.

You will need to quadruple shock your pool by added 4 pounds of shock to every 10,000 gallons of water. This can be expensive if you have a large swimming pool. Just make sure you follow the same procedures.

Cloudy Blue Water?

The goal with using chlorine shock to kill algae is to get your pool to be a cloudy blue color. Blue or white means the algae has been killed. When algae is dead, it turns a gray color.

Now, you ‘ll need to run your pump and filter continuously until the water is clear. You may want to use a pool clarifier to aid in the water clearing process, this may take some time depending on the size and ability of your filter system.

Source: Swim University

About Swim University
Swim University

Swim UniversityThis is a guest post from Matt Giovanisci, the creator of Swim University, an online guide to swimming pool care. He has over 15 years of experience in the swimming pool and hot tub industry. He is also an award winning web designer and has been featured on Martha Stewart Radio as a pool & spa expert.