Green Pool With Cloudy Water

by Lisa & Walter Jackson
(Victoria, Texas)

Thanks so much for your website.

We are new to taking care of a 10,000 gallon in-ground pool. We live in south Texas where it is muggy and hot. Our pool is green and the water is cloudy.

Levels are: 8.4 pH, 10 PPM, 120 Alkalinity, 100 Stabilizer

We shocked the pool. Have vacuumed and brushed sides and bottom repeatedly with no change.

With the pump running continuously, early in the evening we put in pH Minus and waited 2 hours. Then we put 128 oz. of liquid chlorine in, brushed the bottom and ran the pump another 3 hours and turned it off over night.

This morning our pH was down to 7.8 but everything else was the same. We have just vacuumed the pool again.

We are clueless as to what do to next.

Please help :)

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Thanks for the question and glad you found my site

First thing I noticed with your readings was the stabilizer (cyanuric acid/CYA). It's 100ppm, if I read that correctly. The recommended range for CYA is 30 - 50ppm. What's happening is the chlorine is becoming less and less effective the higher the CYA gets. Stabilizer needs to be 7.5% of the chlorine. This is how to control algae.

This is an easy math equation. Say you run the chlorine at 2.5ppm, simply divide 2.5 by 7.5% and you get 33. Now, as the CYA increases through using tabs, Trichlor tabs, the chlorine needs to increase as well.

If you allow the CYA to get to 100ppm, you need to run the chlorine at 7 - 8ppm for the chlorine to be effective. 7 (chlorine) divided by 7.5% (CYA) = 93. 8 divided by 7.5% = 106. When the CYA gets this high the only way to reduce it is a

partial drain and refill.

There's no chemical to reduce the CYA. Let's use common sense. If your CYA is at 100ppm, and the range is 30 - 50ppm, then by draining 1/2 of the water and refilling it you'll drop the CYA to 50ppm. You really want it to get to 30ppm. As was stated above, the CYA will slowly increase using Trichlor tabs.

You can shock the pool and possibly clear it up, however, it will probably go green again because of the elevated CYA level. Doing this will save alot on swimming pool chemicals in the long run.

The best, and really only solution, is to drain about 2/3 of the water and refill. This will keep about 30ppm CYA in the pool. Next is to run the FILTER for 24 hours then retest all of the chemicals. You need to do this because you're adding so much fresh water. The readings you have right now will not be the same after the new refill.

The pool store might tell you to keep shocking the pool without taking into consideration the high CYA. This is completely wrong. You must get the CYA down so your chlorine can work properly.

Do this and email back with the new readings and we can go from there.

To post a reply, or if you have a similar question, you can see your post on the Q&A page in the "Algae/Green Pool Water" category.

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Hope this helps and have a great Summer.

Robert