Swimming Pool Water Chemistry For The Pool Guy (PART 2) – pH
Swimming pool pH
The pH scale goes from 0 to 14 with 7 being neutral. Anything under 7 and the water is acidic and “yes” that is a bad thing. As pool guys, we don’t want the pH ever to be under 7 because of the damages that can happen to a pool and it’s equipment.
What is pH? pH is the acidity of the pool water. If it is under 7 the water is acidic and if it is above 7 the water is basic. As a pool guy when you are testing your pool’s pH you are testing to see how acidic the pool or spa water is. The lower the pH the more acidic the water is and “yes” that is still a bad thing. The reason low pH bad is that acid eats through things. If you allow the pH level of the swimming pool water get low it will damage the plaster and the equipment. It can eat through the inside of a pool heater in no time.
The normal tendency of pH is to rise due to bathers, winds, sunshine, and water added to the pool at a higher pH. But constant lower pH can be experienced due to low Total Alkalinity. We will cover Alkalinity, how its interrelated to pH and why it’s so important in Part 3.
An Acceptable pH for a swimming pool is between 7.2 and 7.8, but the ideal pH is 7.4 to 7.6 ppm. In the swimming pool industry, you will often hear that the ideal range is between 7.4 and 7.6 ppm. If you are one of those pool pros that really shoots to be right on target you will want to be at 7.4 ppm. The reason that the ideal pH is 7.4 is for 2 main reasons. One, the pH of the human eye and mucous membranes is 7.4, and two, chlorine works best with a pH of 7.4 ppm.
When the pool has a high pH you can have scaling/calcium buildup on the pool surface and tile. You can also have cloudy water, clogging of the filter, burning of eyes and nose, and a drop in chlorine effectiveness. If the pH is too high the chlorine will not work as well and be able to do its job effectively. This will not only be an issue with your bather’s safety but also hurt your bottom line since you will need more chemicals to be able to treat the pool properly and will need to deal with its side effects.
Remember as a rule of thumb an acceptable range is 7.2 to 7.8 ppm, an ideal range is from 7.4 to 7.6.
To lower your pH you will normally use an acid solution. In the pool industry, you will normally use hydrochloric acid best know in our industry as Muriatic Acid or sodium bi-sulfate also known as Dry Acid. To increase the pH level you will use Sodium Bicarbonate better know as Soda Ash.
Do not use Baking Soda to increase your pH level. It will affect you Alkalinity that is interrelated with your pH. We will go over alkalinity in Part 3 and the dangers of low alkalinity.