Swimming Pool Stabilizer Levels

A crystal clear backyard pool

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If you had your swimming pool water tested and were told the stabilizer level was too high, you might have been instructed to drain your pool. Most likely, the advice you got was to drain it to a depth of 1 foot in the shallow end, then refill it with fresh water to lower your pool's stabilizer level.

You might wonder whether there's an easier way to get your pool stabilizer level right—like maybe adding another chemical. And, anyway, what's wrong with having a swimming pool stabilizer that's too high?

The Importance of Pool Stabilizer

Chlorine stabilizer or conditioner (cyanuric acid) is used in the maintenance of outdoor chlorine-maintained swimming pools.The stabilizer helps act against the sun's UV rays. Without stabilizer, sunlight can reduce chlorine in your pool by 75 to 90 percent in just two hours. The purpose of the stabilizer is to help the chlorine last longer and protect swimmers. The pool stabilizer binds to chlorine, then slowly releases it, helping the chlorine last longer and reducing consumption.

A chemical test determines the cyanuric acid level. The typical cyanuric acid range is 20 to 40 parts per million in northern areas, whereas southern areas are typically higher, 40 to 50 parts per million. This difference is attributed to the amount of sun exposure. Simply put, the southern areas typically receive more sun. If the levels of cyanuric acid in your pool are between 80 and 149 ppm, it is not ideal, but it is also not considered a serious problem. However, if your pool stabilizer level hits 150 parts per million or higher, the effectiveness of the chlorine is reduced, and you need to take action to bring the stabilizer level down.

Problem With Too Much Stabilizer

Generally speaking, you would like your swimming pool stabilizer level to be below 100. When your pool has too much cyanuric acid, chlorine doesn't do its job. Specifically, it is ineffective against dangerous microorganisms like cryptosporidium parvum. Too much stabilizer can also damage the plaster surfaces of the pool and can lead to cloudy water.

To drop the stabilizer level, the standard procedure is to drain the pool and refill it with fresh water. But in areas where there's a water shortage, draining the pool might not be an option. There are, however, microbial and enzyme products on the market called cyanuric acid reducers that offer varying degrees of effectiveness. They work by decomposing the cyanuric acid.

If you want to drain the pool, be very careful not to take too much water out (no more than a foot) and be sure that you do not have a high groundwater table. Whenever draining a pool, it is really important to stay by the pool while it is draining. Draining the pool too far and causing a hydrostatic heave can happen on any pool type: concrete, vinyl, and fiberglass. 

Be aware of your state and local laws regarding the draining of your swimming pool. It's not just a water conservation issue—pool water can pollute the environment, affecting plant life, fish, and other wildlife.