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Why is My Pool Water 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. Which ever leads, all I pH and TAknow 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) .

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

How to Maintain Proper Pool Water pH Levels

In reading around on the internet, I read the phrase “carbon dioxide out gassing” 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 out gassing is alkalinity. Apparently high total alkalinity levels (TA) assists with carbon dioxide out gassing which then raises pH. So, lowering the alkalinity levels helps to reduce the rate of out gassing 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 ProblemAdding Water to the Pool

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

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.

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  1. TAMATHY says:

    WELL HOPE YOU CAN HELP,WE HAVE A 24 FT POOL THAT HOLDS 15,000 GALLONS OF WATER SO I,AM TOLD ,WE ARE HAVING A HUGE PROBLEM WITH ALGAE THE YELLOW KIND. WHEN IT RAINS THE WATER TURNS GREEN AND THEN WE ADD CHLORINE AND THATS GOOD BUT WE STARTED NOTICING A RING AROUND THE BOTTOM OF THE POOL THAT WILL NOT GO AWAY AND THE MORE THE MORE ALGAE, WE DO HAVE WELL WATER WITH SALT SOFTNER . PEOPLE HAVE SUGGESTED MANY THINGS TO TRY AND WE HAVE BUT NOTHING IS WORKING IT,S JUST COSTING ALOT OF TIME AND MONEY THAT WE DO NOT HAVE ANY MORE,SO IF YOU HAVE ANY SUGGESTIONS WE COULD SURE USE IT.PLEASE HELP

    • Hayward says:

      Tamathy, I feel your pain.

      I’m not so sure I’ve had yellow algae, although my green algae as it started to get better looked a bit yellow. I’m also not sure what the ring is at the bottom of the pool. I can only give you advice from my own experience.

      I have town water but I do use a salt softener. The softener does cause the pH to rise, but your problem sounds like you’ve got to put your pool on a shock diet.

      When my pool was cloudy, green and brown, after I removed all of the dead leaves, I started adding a bottle or two or three of shock every day and ran the filter 24 hours a day for about a two weeks. My pool was in very, very bad condition.

      Try maintaining extremely high chlorine levels for about a week or so and keep the pool filter running. You should begin to see the algae begin to clear up. Additionally, make sure to sweep your pool thoroughly. Sweep the walls, bottom and ladder. You want to dislodge any algae that wants to grow. After sweeping the pool allow the filter to continue running and then vacuum out the pool. Also, after you vacuum the pool, you should give your filter a good cleaning.

      The problem you’re having sounds to me that the chlorine levels have been allowed to dip too low. Once they dip too low, algae gets a chance to grow.

      A question for you: How many times a day to you test your pool water and what are the chemical levels?