Pool School 103 pH

When it comes to the terminology of pH understanding it can be confusing, however if you pay close attention I think this class will clear things up nicely.

When we are talking about pH we are talking about the amount of hydrogen that is in the water. This level directly affects your sanitizer’s ability to do its job. So it is vitally important that you keep a close eye on your pH level and adjust it when necessary. The range for pH is 0 (being perfectly acidic) to 14 (being perfectly alkaline). The ideal range for your swimming pool is 7.4 to 7.6. The pH of your eye is 7.4 so if you go below 7.4 on pH you may encounter eye irritation. If you have see the eye wash commercials that ask you if the chlorine in the pool is burning your eyes, don’t believe them it is the pH that is burning your eyes not the chlorine and if the pool you are swimming in is irritating your eyes then the pool water is not properly balances and it is time to get out of the pool. The pH can either be acidic or (and this is where people get confused) alkaline. People will confuse the water being alkaline with the mineral balance “Total Alkalinity” (which we will talk about in Pool School 104). When the pH is below 7.0 the water is considered acidic. When the pH is above 7.0 the water is considered alkaline. 7.0 is perfectly neutral, the water is neither acidic nor alkaline.

The pH will only change when it is affected, in other words something has to be added to the water to make pH change. The method of sanitizing your pool is the most common cause of pH fluctuation. Different methods of sanitizing will affect the water differently. I am going to talk about the three most common methods of sanitizing, Chlorine Tablets, Salt Generation and Biguanides.

Chlorine tablets have a pH of about 2.0. That said when you dissolve a chlorine tablet into the water it is going to lower the pH level. When the pH level drops below 7.0 and the water becomes acidic lots of bad things begin to happen. First thing you will notice, as I mention before, your eyes will begin to burn and turn red from the irritation. This is kind of the canary in the mine situation. If you see this happening do a test with your test kit then adjust the pH as soon as possible. One of the other bad things that happens is the Total Alkalinity will begin to be dissolved by the acidity of the water and thus make your pH more difficult to control (we will talk more about this next week). Also when the pH drops below 7.0 the water will begin to etch away at everything metal in the pool and the filter system including; handrails, ladders, bolts and nuts, shaft seals in pump and spring in your multiport valve. Plus low pH levels will begin to make all plastics more brittle over a period of time and also negatively affect any pool surface.

Salt generators have opposite effect on the pH from chlorine tablets! So as the units make chlorine the pH level is increased as a side effect. This sounds great until you realize that as the pH increases the ability of chlorine to sanitize the water decreases. As you get up to the 8.0 range the chlorine is not effectively sanitizing the water. So it is important that you adjust the pH level about once a week when you have a salt generator. When the pH is about 7.8 your cell could begin to form scale which is not a good thing because it will require you to acid wash the cell, which in itself is not good for the cell but if it is scaled it will be necessary. So just to restate it you should keep a close eye on the pH and adjust it when necessary.

Biguanides have no effect on the pH level. However if the pH gets about 8.0 it could cause cloudy pool water. So just like all other systems it is important to keep an eye on the pH level and adjust it if necessary.

There are other things that affect the pH level like rain (which is usually acidic, below 7.0) and chemicals that you add to the pool water will have an effect on the pH. As we go through the pool school series I will talk about each product effect on the pH. So make sure you are on time for the next class!

pH Scale

This chart will give you a visual comparison for the pH of different products.


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