What is pH and how does it relate to your pool? pH is the measurement of how acidic or basic water is. The quick rundown for pool owners is that the lower the number, the more acidic the water is, while the higher the number, the more basic it is. The human body is right around 7.4 and ideal pH levels in pools is between 7.4 and 7.6, so that the water is comfortable to be in.
When pH drops below 7.0 it becomes acidic. This can have a multitude of negative effects, some of which are degradation of the plaster to burning of your eyes and skin. Any metal equipment, be it a ladder, some plumbing, or more critically, a heater or heat pump, will start to strip the lower the pH is.
On the opposite side of the scale is pH that is left uncontrolled which will turn the water basic and can create scale on the plaster and dry your skin and eyes when you get in the water. Too high of pH will also render your sanitizer useless and is a breeding ground for bacteria.
pH is kept in check with regular testing and should be checked as often as chlorine levels are tested for. If your pool is treated with liquid chemicals then muriatic acid is usually used to prevent the pH from rising above the top ideal number of 7.8. If using tablets as the main source of treatment for the water, then you run the risk of dropping the pH too low, especially during summer when using more than one tablet at a time. This will require sodium bi-carbonate (baking soda works the same) or simply aerating the water will naturally raise pH. Keep in mind that if you have a fountain, water sprayer, or jet that pushes water into the air and bubbles back into the pool, you will be raising the pH the entire time that feature is running.
When discussing pH in pool chemistry, it is important to also talk about alkalinity. Alkalinity typically rises and falls with pH levels and acts as a buffer to the water’s pH so that anything that is added to the water doesn’t rapidly change the pH. For example, liquid chlorine has a pH of around 3 and every gallon can affect the pH level of the water, but alkalinity is present to make sure it doesn’t drop to an unsafe level.
Let’s talk very quickly about LSI or the Langelier Saturation index. This is an equation that uses a few different factors to determine if the water is corrosive or is scale forming. The largest numerical value of the equation is temperature. What that means is that the equation has to stay balanced, whether it is summer or winter, and pools that stay open year round can see a 40 to 50 degree temperature variation between winter time temps and summertime temps. To keep the LSI balanced, it is recommended to keep pH at ideal levels for swimming (7.4 – 7.6) during summer, then during winter as the water gets colder, you want to let pH rise a bit, as no one is using the pool anyway.
As with any chemical balance, Total Dissolved Solids, or TDS, will play a role in being able to maintain pH. If your TDS gets over 2000PPM from what your tap water (or fill water for the pool) is, it is time to drain and refill the pool as the water will essentially lock out chemicals and their ability to control the balance.
One last point to keep in mind when keeping pH at the correct level in your pool is parties. When you have a decent amount of people in your pool those bodies will deteriorate the sanitizer levels as well as raise the pH. It is very important to check the water composition after a party and adjust accordingly to keep it balanced and the water clear. One recommendation we have it to add an extra gallon of chlorine the day before the party to make sure sanitizer levels are up to counter the sanitizer usage when bathers are swimming.
While pH doesn’t get the same recognition as chlorine to keeping your pool water clear and feeling good on your skin, it’s just as important to check and adjust as necessary.
