Last Updated: February 21, 2020
So, the pH in your pool is too high and you want to lower it? Good for you! You should lower it, but before we get to that, and how to do it, let’s get take a quick refresher course, courtesy of the University of Massachusetts at Amherst.
“pH” stands for “power of hydrogen”. The pH scale measures the logarithmic concentration of hydrogen (H+) and hydroxide (OH-) ions. This is water, (H+ + OH-) = H20. When both types are equal in concentration, the pH is 7.0, which is considered neutral.
When the concentrations aren’t equal, that’s where the problems start. PH is ranked on a scale from 1.0 to 14.0. The lower the pH of water, the more acid is in it, or the more acidic the water is. The higher the pH, the more base, or alkaline, it is. Our friends at UMassAmherst tell us, “pH affects many chemical and biological processes in the water and different organisms have different ranges of pH within which they flourish.”
First of all, consider that the pH of human teardrops is about 7.5. Having a pool pH as close to that number as possible will make swimming more comfortable. We often hear people complaining about the chlorine level in the pool hurting their eyes, but the truth is, unbalanced pH levels, not chlorine, is almost always the problem. So that’s number one.
Number two is that high pH can cause all sorts of problems in the water, and in your pool equipment. High pH can lead to scaling, which in turn leads to clogged filters, reduced circulation, and if you have a heater, it can clog the heating elements in it too. High pH also leads to cloudy water and impaired functioning of the chlorine in the water. In addition to eye irritation, high pH can also irritate your skin.
Since high pH means the water in your swimming pool is too alkaline, you need to add acid to the water to lower it again. These acid chemicals are sometimes referred to as pH minus, pH decreaser, and pH reducer. Regardless of the name, there are two basic types of acid for use in swimming pools; Sodium Bisulfate, also known as dry acid, and Liquid Hydrochloric, also known as muriatic acid.
Acids are dangerous chemicals that can burn and scar flesh as well as cause damage to pool liners, equipment, clothes, and anything else it comes in contact with. Therefore you need to exercise extreme caution when dealing with it.
Although the percentage of sodium bisulfate will differ from manufacturer to manufacturer, the most common percentage is around 93%. The amount you’ll need to add to your pool will vary depending on the pH level you measure with your testing kit and the specific percentage in your product. The instructions on the label will tell you exactly how much of that particular product to use, so read them carefully and never assume you can use the same amount from one brand to another.
Sodium Bisulfate comes in a powder. Don’t put it out on a windy day because it can blow back all over you, your clothes, pool deck, and equipment. If you live in a windy area – like Chicago – stand upwind to pour it into the pool, and keep the container as close to the water as possible.
Pour about three-fourths of the recommended amount of the powder into the pool right at the water return jets so it will be quickly spread around the entire pool. If there’s no wind, you can sprinkle it in the water all the way around the pool to accomplish the same thing. If three-quarters of it aren’t enough you can always add more of it later, but adding too much will cause problems on its own, so play it safe.
Allow two to four hours for the chemicals to mix then test it again. If the pH is still too high, you can add a little more, wait two to four more hours then test it again.
Muriatic acid is more dangerous than dry acid because it’s a liquid that will cling to your skin and clothes if you get it on you. You should definitely wear protective gear when working with it.
As with the sodium bisulfate, add three-quarters of the recommended amount at the pool return jets or evenly scattered around the pool. Wait two to four hours then test the water. If the pH is still too high, repeat this process using successively smaller amounts of acid until the water has finally been balanced.
Although it’s safe for swimmers to go back in the water within two hours, you should keep everyone out of the pool entirely until the pH levels have been brought back under control. Swimmers can introduce contaminants into the pool from particulate matter on their suits, their skin, or hair.
It’s best to keep the variables in this equation down to a minimum until the process is done. Your pH levels will be controlled much more quickly and easily that way.
Header image credit: Roger W, Flickr
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