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Why is My Pool Water pH Rising?

by Felicia A. Williams

Why is my pool's pH rising?I’ve figured out how to get my chlorine levels to stabilize, more or less, in my pool, but how do I get my pH levels to remain within range. It seems that the numbers rise almost daily. I’ve been adding pH Decrease (which is basically muriatic acid) to bring the pH levels down only to find in the next day or so the levels are rising again.

pH and Alkalinity the Nefarious Duo

When pH goes up it takes its partner Alkalinity along too, or maybe it’s the other way around. Whichever leads, all I know is that it ends up with high readings for both.

Since chlorine depends on proper pH (not alkalinity), I’m more concerned with getting the pH to stabilize at the proper level. I also understand that having proper alkalinity levels helps to keep the pH in the proper range. Total alkalinity seems to have a buffering effect on the pH to prevent the dips and spikes (spikes in my case).

How to balance the pH

To balance the pH (which brings the alkalinity levels down), you have to add muriatic acid. If your pH levels are low, add soda ash instead.

I’ve found that I’m adding a pound of muriatic acid every two days or so to bring the pH levels down. As we have already discussed a high pH level takes some of the power out of the chlorine which means it won’t clean as well as it should (low pH causes the chemicals to dissipate more quickly).

pH and Alkalinity

After having had a green pool I don’t want to give algae a chance to grow so proper chemical levels are very important to me.

How to Maintain Proper Pool Water pH Levels

In reading around on the internet, I read the phrase “carbon dioxide outgassing” which leads to a rising pH. In other words, as carbon dioxide gas leaves the water, the pool’s pH levels rise. Hand in hand with outgassing is alkalinity. Apparently high total alkalinity levels (TA) assists with carbon dioxide outgassing which then raises pH. So, lowering the alkalinity levels helps to reduce the rate of outgassing which helps to maintain a level pH.

Now, which came first, the chicken or the egg? Reducing TA is rather difficult to do without lowering the pH beyond acceptable ranges. When I get my pH into an acceptable range the TA is always slightly high, about 170 to 180 ppm. I don’t fret over it because it’s the pH I’m worrying about. However, I found a very interesting article on how to lower the pool’s TA.

I haven’t tried the method and don’t know that I will because the second part of my problem is my fill water.

Adding to the pH Alkalinity Problem

Just for grins, I tested my house water’s pH and TA and I found one part of my problem. My house water’s pH is at the top of the chart and so is the alkalinity. My water treatment system which softens my house water does so by raising the pH and alkalinity. That’s the very same water I use to fill and refill the pool when water levels get low.

In essence, I’m introducing my pH problems to an already problematic situation.

My Solution to the Rising pH Problem Adding water to the pool

Just like adding fuel to a car to make it run, adding charcoal to a grill for great chicken or cleaning the house, it’s just one of those things that must be done. If I want to have a pool with clear, bacteria-free, algae-free water, I’ll have to monitor the pH levels and add pH Decrease when necessary.

In the grand scheme of things, it’s not so bad, just a cost of doing business.

About the Author: Felicia Williams is a wife, mother and grandmother who likes to write about a host of topics.


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Last Modified: 26 January 2020

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