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Green Swimming Pool Help: How to Clean & Get Rid of Algae

Help! My swimming pool turned green!

Help! My swimming pool turned green!

How to Fix or Prevent a Green Pool

  1. Balance pool chemistry
  2. Balance PH levels
  3. Check the filter
  4. Thoroughly scrub the pool clean

Below are detailed instructions for these steps as well instructions to shock your pool after a full algae outbreak.

Step 1: Balance the Pool Chemistry

First and foremost, test both the chlorine and pH levels of the water. There is a high potential for algae to grow when chlorine levels are below 1.0 parts per million (ppm). If the levels do get below 1.0 ppm, then the water will eventually turn green. It should be noted that even a few days without proper pool maintenance can result in a green pool due to algae growth.

Chlorine levels should be between 1.0 and 3.0 ppm. These are safe levels for swimming. Too much chlorine can be bad for a person's skin and eyes. High chlorine levels can also damage the lining. Balance is key.

As for pH levels, 7.0 to 7.6 is the ideal range. This is because the pH of our eyes is about that level. When pH levels are too high it can cause skin irritation and burning red eyes. Also, if levels are really high then chlorine will not sanitize the water.

If you are trying to treat algae, however, pH levels need to be higher. The range for treating algae should be around 7.8-8.0

Step 2: Balance the PH Levels

Add acid or a base to the pool until levels are at 7.8 or 8.0. And turn on the pump. This will allow the chemicals to circulate around the water. In order to balance the pH levels, increase pH with sodium carbonate or decrease it with sodium bisulfate.

Step 3: Clean the Filter

Make sure that the filter is not clogged by any various types of debris like sticks, leaves, or any other obstruction that may be causing it to become clogged. Always make sure the filter is working properly before adding any types of chemicals to the water to kill algae. If it is necessary, backwash the filter.

Have the filter run for 24 hours per day so you will be able to get rid of the algae during the cleaning process.

Step 4: Thoroughly Scrub the Pool

Although chemicals in the water will help get rid of the algae, scrubbing the sides and bottoms of the pool will speed up the process. Algae often sticks to the surfaces and scrubbing can loosen up the algae so the chemicals will work more optimally.

Look for areas that have a high amount of algae and scrub those particular areas. Be careful when choosing a brush. Do not use wire brushes for vinyl pools. Use a nylon type of brush. Wire brushes can possibly damage vinyl, fiberglass or tiled pools, however, they are okay to use in plaster types.

How to Shock a Pool

Use pool shock to destroy the algae and sanitize the water. Try and find a pool shock that has about 70-75% chlorine in it. This will be powerful enough to get rid of algae and bacteria.

What You'll Need

  • Shock with at least 70% chlorine
  • Protective eyewear
  • Rubber gloves
  • Stirrer
  • 5-gallon bucket
  • Old clothes that you don't care about much because shock contains a lot of chlorine, which can bleach clothes.

How to Shock a Swimming Pool

  1. Fill a 5-gallon bucket with water.
  2. Add 1 pound of shock to the bucket.
  3. Stir the shock slowly to prevent splashing.
  4. Make sure the pool is running.
  5. Shock water at night or dusk (recommended) and let the pool run for 8-10 hours overnight.

Shock your swimming pool by pre-dissolving each pound of shock in a bucket of water before adding it to the water. Add shock to the water, not water to the shock! Pour the shock around the pool slowly to prevent splashing (or at least minimize it). Use one bag of shock per 10,000 gallons of water because one bag treats approximately that much.

If your water has a high amount of algae, then you might have to treat the pool more than just one time. Otherwise, the algae might spawn again. Don't worry if the water looks cloudy and murky after adding the shock. Once the water runs through the filter for a while, the water will eventually start to look clearer.

Once the chlorine levels are below 5.0, use algaecide, and allow it to work through the water for 24 hours or so.

Brushing and Vacuuming the Pool

Use a brush and a vacuum to clean up any dead algae. Make sure to clean both the bottom and sides of the pool. If you are having trouble removing the dead algae, you can use flocculant. Flocculant bonds contaminants together to make algae easier to remove.

After this treatment, the water should be crystal clear. Check the chemical levels to ensure they are in the normal range. If algae comes back, you can go through the process of shocking the pool again.

Beautiful blue pool. Who's ready for a swim?

Beautiful blue pool. Who's ready for a swim?

Why Is My Pool Green After a Heavy Rain or Thunder/Lightning Storm?

A common question many people and pool owners may ask is, "Why does my pool turn green after a heavy thunderstorm?" First of all, strong winds can cause dirt and debris to fall into your pool. Normally, on a low wind sunny day, this is not so much an issue. But during a thunderstorm there is a much greater chance that dirt and debris will get into the water. And of course, the rainwater affects the water chemistry as well, which is why the water may turn green.

Also, even lightning can affect the color of your pool. Don't believe that? There is an explanation! The lightning affects the nitrogen levels. This will will make algae turn even greener.

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.


Jerry on August 02, 2017:

What is your recommendations on keeping a pool clean during lots of rain? We finally got rid of the yellow algea and now we can't seem to keep the pool clear from the green algea.

phil greco on July 06, 2017:

pool was clearing started cleaning it turned light green.

put in green out and then shock it turned pea green it foamed after using black magnet. It's to costly to clear the pool out

should I just use gallons of bleach.

Cindy on May 26, 2016:

Can you use a spa algicyde in a pool?