pH stubbornly high despite muriatic acid

[Mimi Pool]

Despite reluctance we've used muriatic acid in attempting to lower pH. CYA is always a problem despite not using pucks (except during one weekend trip), it was 40 when the pool was opened May 3 then reached 80 by May 29 where it has remained. CH has been consistently 250, TA 80-90, FC in the recommended range based on FC/CYA chart. pH has been stubborn - since June 2 it has been in the range of 7.8 to 8.0. We bought a gallon of muriatic acid June 25 and added at different times based on the old Pool Math page with a target of 7.6. As of this past weekend, the whole gallon is gone and pH has never gone below 7.8. Nothing critical - the CSI has been 0.1 or less.
We weren't real keen about muriatic acid in the first place, now even less so since it doesn't appear to work for us. Someone responded to another of my posts saying they let it get up to 8.0 then knock it down to 7.6. Could this issue be something unique to our pool or should we try a different chemical like dry acid?

 

[ajw22]

Do you test the pH 30 miuntes to an hour after adding the acid to know what the pH was lowered to?

As soon as you lower the pH it begins rising. You can't judge the acid effectiveness a day or two later.

 

[Texas Splash]

There really is no need to get overly aggressive with acid based on your numbers. A pH of 7.8 is fine, and your TA numbers look good as well. Simply adding a little acid once or twice a week to keep the pH around 7.8 is fine and normal. I think the comment you were referring to from another post was actually to lower the TA. That process requires letting the pH rise to 7.8-8.0 and knocking the pH down to about 7.2. But again, you don't appear to need that at this time.

The other concern is your CYA. It was 40, but now is 80? You mentioned not using pucks, but the CYA won't go up unless someone added a stabilized form of CYA (bags of shock, etc).

 

[Mimi Pool]

Yeah, I don't get what is happening with CYA. Going back to when the pool was opened, testing showed FC 0.2, pH 7.5, TA 40, CH 100, CYA 40. After opening we added one gallon of liquid chlorine and two 1 lb bags of Cal Hypo 57.8% which we regretted since FC jumped to 8.8 (no big loss water temp was 55 degrees and it dropped to 5 within 3 days). We put in baking soda, calcium chloride, and within a week testing showed TA 90, CH 250 but pH had shot up to 8.0 and CYA to 60. The Cal Hypo (Burnout 3) is not supposed to have stabilizer. We had Low N Slo left over from last year and used it to lower pH to 7.7.
We went away that one weekend 2-3 weeks after opening and used pucks in the chlorinator while gone and that is when CYA jumped to 80. Three pucks went in, not even a full one was used up when removed.
We did not follow the process suggested by ajw22 - chemicals typically go in evening time after the sun is off the pool, testing done in the morning.
I'm going to conclude that Texas Splash comments caused me to deep dive on what has been put in (aided by Pool Math app) and will conclude that the rise in CYA has to be due to the shock and pucks. Maybe something in the calcium chloride (used Driveway Heat) and Lo N Slow contributed. We're also not going to sweat the pH unless it goes over 7.8 then we'll have to revisit because my husband is very anti muriatic acid.

 

[Nikilyn]

Why is he anti MA? I’m just curious because I’ve never thought about it being a bad chemical. It’s just something we need to use regularly because we have a waterfall we like to use that raises pH.

 

[borjis]

I've noticed since installing a replacement pump motor, mine is rising too and it never did before.
My old motor was a bit "tired." The new one has the return jets making a more agressive splashing on the surface. I'm pretty sure that is the cause. pH was rock steady at 7.5 for 5 years prior.

Maybe something like that is affecting your pH?

I'm getting in today to loosen the eyeballs and move the jets down a little.