Swimming Pool Stabilizer Levels

Why a High Stabilizer Level is Bad for a Pool

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A reader asks: I had my swimming pool water tested and my stabilizer was 135. I was told I needed to drain my pool to a depth of 1 foot in the shallow end, then refill with fresh water to lower my pool's stabilizer level. Is this correct, or is there a chemical that can do it? Why is it bad if my swim pool stabilizer is too high?

From About Swimming's Swimming Pool Expert, Ray Cronise:

First, understanding chlorine stabilizer is important.

Chlorine stabilizer or conditioner (cyanuric acid) is used in the maintenance of outdoor chlorine-maintained swimming pools.The stabilizer helps act against the UV rays. The purpose of the stabilizer is to help the chlorine last longer and prevent consumption of the chlorine. This helps the chlorine last longer and reduces consumption. A chemical test determines the cyanuric acid level. The typical cyanuric range is 20-40 PPM in northern areas, where southern areas are typically higher, 40-50 PPM. This difference occurs from the amount of sun exposure, with the southern areas receiving more sun. If the levels of cyanuric acid are between 80-150 PPM, it is not ideal, but not considered a serious problem. However, if 150 PPM occurs, the effectiveness of chlorine is reduced and maintained is often required.

Generally speaking, you would like your swimming pool's stabilizer level to be below 100 (80-100 range).

Keep in mind that stabilizer allows your chlorine to hang around longer in the pool water. This is especially important on hot summer days. UV of the mid-summer can quickly consume chlorine in the pool. One of the big advantages of a salt chlorinator is that it is constantly supplying chlorine and the rate can be increased during the high demand of the mid-summer season.

It is not a bad idea to drop the stabilizer level. Too much can lead to cloudy water and it also decreases the effectiveness of the chlorine (although you are not at those levels yet). There are some commercial municipalities that have increased maximum levels to as high as 200 ppm for public pools.

If you want to drain the pool, be VERY cautious not to take too much water out (no more than a foot!) also be sure that you do not have a high ground water table. Whenever draining a pool, it is REALLY important to stay by the pool whenever it is draining. Draining the pool too far and causing a hydrostatic heave can happen on ANY pool type: concrete, vinyl, and fiberglass. Please proceed with extreme caution when draining water from your swimming pool.