How to Get Rid of High Phosphates and Stabilizer in a Pool

Updated on March 5, 2018

Keeping the Balance

It can be a challenge to keep the chemicals in your pool in perfect balance, but it's important for many reasons. Number one is your health. Balanced chemicals also help to keep your water clear and free of algae.


We will take an in-depth look at some advanced swimming pool water chemistry. Many people have problems balancing the pool water because they are unaware of the many factors involved in water chemistry.

Three elements, pH, chlorine, and alkalinity, are each important. It can be a struggle to keep them in balance if there are other chemistry issues going on. This other chemicals include phosphates and stabilizer.

First let's explore phosphates, also known as phosphorous. Phosphates can enter the pool a few different ways. The most common cause is leaves and organic debris. Another less common way is when lawn technicians or a gardener spray your yard while there is a breeze. Some of the chemicals used for fertilizing a lawn or shrubbery can contain a high amount of phosphorous. So what does a high phosphate count do to the pool? It can create algae problems. Algae feed on phosphates and warm water. A good balance of just chlorine, pH, and alkalinity are not enough to counter-balance the effects of high phosphates. Shocking the pool will temporarily help, but the algae will return.

High stabilizer can cause other problems as well. This article explains more about stabilizer and how to tell if your pool's levels are too high. Also known as cyanuric acid, high stabilizer can essentially lock the chlorine molecules, rendering the chlorine useless as a sanitizer. This can lead to algae problems. The most common cause of excessive stabilizer levels is the use of chlorine tablets (tri-chlor), which contain stabilizer.

Testing for Phosphates and Stabilizer

Most of the 6-way test strips do provide a stabilizer reading. I highly recommend a professional dpd test kit such as the Taylor complete. It is the same test kit the pros use with very high accuracy on your readings. The Taylor kit includes free and total chlorine, bromine, pH, alkalinity, stabilizer, calcium, and acid demand tests. Test strips are cheap, but you will never really get an exact reading, they just give a general idea whether a chemical is high or low. In any case, if your stabilizer is high, it will need to be lowered to a more manageable level (between 30 and 50ppm) Pool water will need to be diluted with fresh water in order to lower it.

Testing for phosphates requires a separate test kit. Since it takes time, many months or even years for phosphates to reach a high level, it is easiest to go to your local pool store with a water sample and have it checked rather than purchasing a phosphate test kit. Getting rid of phosphates is very easy. There are products that can be added to the water that will take care of the problem effectively. I usually use a product called "Phos-Free" available at some pool stores, or you can purchase on eBay.

Calcium in the water is very important. If maintained at the proper level, calcium will greatly extend the life of the pool surface. Why? High calcium levels can cause scaling while low levels will eat at the plaster. Water needs calcium. Without added calcium, the water will pull it out of the pool walls, causing damage. The ideal calcium range is between 220-400ppm.

Calcium, like stabilizer, can be added to the pool, but in order to lower it, the pool water must be diluted. Again, this is where test strips can be frustrating since you really don't know exactly what your reading is.

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