[RESOLVED] What is causing pH constantly going up?

[Jerryxe]

Hi,

I noticed that my pool's pH always gradually goes up, and I have to add muraatic acid almost every 1-2 weeks.

E.g. below are recent test results from Taylor K-2000C:
- Jan 4th, pH 8.1, then added 24oz 31.45% muratic acid
- Jan 5th, pH 7.5
- Jan 6th, pH 7.6
- Jan 7th, pH 7.7
- Jan 10th, pH 8.0
- Jan 13th, pH 8.2 (Estimate, since it's way above the K-2000C color bar)

And this has been happening in the past few months (new pool for only 4 months), and I have to add muratic acid every 1-2 weeks to keep it at ~7.5.

Any idea why? During the 4 months, half of the time I used SWG (summer), and half of the time I used in-line chlorine feeder with 2-in tabs (winter, water temp is ~45-50F), and kept FC at 9-10.

Our city water is pretty hard, test shows CH is ~600

Thanks!

 

[Jimrahbe]

Jerry,

Sounds pretty normal for a new pool...

There is just no reason to force the pool to stay at 7.5... Anything in the '7's' is perfectly fine.

I keep my TA at about 50.. What is your TA???

Thanks,

Jim R.

 

[JamesW]

 

[sande005]

It is your TA at 120 that is causing the rise. It takes a while, but adding the acid will slowly bring the TA down. Once in the 50-70 range, the pH will get pretty stable in the high 7's. . Still need to monitor, but the acid need will be much, much less.

 

[Jerryxe]

Jerry,

Sounds pretty normal for a new pool...

There is just no reason to force the pool to stay at 7.5... Anything in the '7's' is perfectly fine.

I keep my TA at about 50.. What is your TA???

Thanks,

Jim R.

Hi Jim,

My TA is usually around 100-110. Guess that's the reason pH goes up?

 

[Jerryxe]

It is your TA at 120 that is causing the rise. It takes a while, but adding the acid will slowly bring the TA down. Once in the 50-70 range, the pH will get pretty stable in the high 7's. . Still need to monitor, but the acid need will be much, much less.

Looks like I missed the TA part... Thanks for pointing it out. I will work on lowering TA first

 

[PoolStored]

Looks like I missed the TA part... Thanks for pointing it out. I will work on lowering TA first

You have a new pool. That by itself will raise pH. It may be 6-18 months before is slows down.

Additionally, you likely have high TA fill water. Test the TA of your fill water and report back.

You lower TA by managing your pH. When you lower pH with muriatic acid, you also lower TA. When you lower your pH, lower it to 7.4, allow it to rise to 8, then lower to 7.4 again. Doing this will lower your TA.
When your TA gets to 60-80, STOP lowering pH to 7.4 and only lower to 7.8. Aside from the new pool issue, with a TA of 60-80, your pH should be fairly stable around 7.8-8.0.

 

[pjt]

I noticed that my pool's pH always gradually goes up, and I have to add muriatic acid almost every 1-2 weeks.

Very normal. During the summer, I add MA around twice a week.

Our city water is pretty hard, test shows CH is ~600

Consider a water softener for your fill line. Small RV water softeners are available.

My TA is usually around 100-110. Guess that's the reason pH goes up?

Yes. What's the TA of your fill water? Under normal circumstances, you should never need to add baking soda.

I will work on lowering TA first

You don't need a dedicated effort to lower TA. It will come down slowly with the MA you add to lower pH. Once TA is in the 50-60 range, your pH rise will be minimal.

 

[JamesW]

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[an1vrsy]

Here in the NW Las Vegas valley we have high TA 140 ppm fill water. I believe it is probably the same throughout the valley.

The frequency of MA additions will/should increase with high evaporation during the summer. It should slow down during this time of year.

With our high TA fill, MA additions every other week is not that bad for our area.