Can't Get Chlorine Levels Down In Pool..High Chlorine

by Linda
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I can not seem to get the chlorine level down in my in ground pool now going on two weeks.

It remains at 10.00 when I test it. I took a sample to the pool store and they confirmed the same thing. Said to leave the tabs out, and the sun will eventually bring the levels down.

Although they did think it was unusual to go on this long. The pH was low, and has been adjusted, but still the results are high. The pool was shocked about two weeks ago, tabs removed from skimmer for four days now, and still high readings.

The pool place said you could use a stabilizer but that could mess with the chemistry of the water. The water is crystal clear, no chlorine smell and you wouldn't have known had I not tested it. Help please! I am kind of a newbie at this, as my pool service guy said I could do it on my own and just have to test for pH level and pool chlorine, so that is all I know.

Thanks for the questions Linda

Not to worry because this site has all you need to have the best pool water chemistry. I would encourage you to get a Taylor Reagent FAS-DPD K-2006 pool water test kit. It's the best on the market and the one I use. It's also the one the Oregon Board of Health uses when they come and test the YMCA pool.

Water Testing Kit

Your pool chlorine level can’t go up without adding chlorine to the pool. Using the FAS-DPD test kit, you can test the swimming pool for cyanuric acid (CYA). This is the stabilizer for your chlorine and it should read between 30ppm – 50ppm. This is a very easy but very important test to take. To adjust your pH pool level you can go to this link:

Swimming Pool pH Levels

There are two ways to lower the pool chlorine:

One is to drain about 1/3 – 1/2 of the pool water, re-fill, then re-test the chemicals. The other way is to use a product called Thiosulphate, which can be found at most pool supply stores. Simply follow the directions on the package. Thiosulphate is a chlorine neutralizer. I would strongly discourage you to put chlorine tablets in the skimmer. Get a chlorine dispenser or float and keep it full of tabs.

Test your CYA at least bi-weekly as the tabs have the stabilizer (CYA) in them and your CYA can get out of hand quickly if you don’t stay on top of that. There are chlorine tablets that say they stop dissolving when the pump motor is off, but better safe than sorry. Get a chlorine tab float.

Your filter stops running but the tabs keep dissolving in the skimmer. When the pump motor starts back up again the filtration system will get a highly concentrated dose of chlorine and acid which, in time, will eat away at the gaskets and O-rings.

If the CYA get too high, say over 90ppm, the best way to reduce it is to drain some of the water and re-fill and re-test all the chemicals. If your pool guy says that the only thing you need to test for is the pool chlorine and pH level, he wants to sell you more and more chemicals.

You need to test for the following:

Chlorine 1.5ppm – 3.5ppm

Combined chlorine (chloramines) 0.0ppm – 0.5ppm

Alkalinity 80ppm – 100ppm

pH 7.6ppm – 7.8ppm

Calcium Hardness (mainly for plaster pools) 150ppm – 250ppm

You’ll find all the information you need and the links to the pages here:

Swimming Pool Chemistry

Swimming Pool Tips

If your pool has that high of chlorine level, there's no reason to shock the pool. Shocking should only be done when the chloramine level gets about 0.5ppm, and the FAS-DPD kit has that test. Also, if you have a cover on the pool, it might be good to leave it off as this will help in burning off some of the chlorine. Hope this help and let me know how this turns out for you.

Have a great Summer


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