Ph keeps going up

[noturbizniss]

My ph was reading 8. 2 or higher. I added 4 lbs of the ph down to the and got it to 7.6 a week later it's up to 8.2 to I added a quart or so of muriatic acid (the concentrated stuff) and was down to 7.4 or 7.6.
A week later and AGAIN its at 8.2 it higher. All I add is liquid chlorine. Haven't added too much water myself (local water is hard) as we got a decent amount of rain a week ago.
My alkalinity is 70.
Any ideas what would be causing this?

 

[ajw22]

How old is your plaster?

What is the pH and TA of your fill water?

It is normal to need to lower pH in some plaster pools once or twice a week. Try and leave your pH at 7.8. No reason to lower it more. pH of 7.4 - 7.6 rises more rapidly.

 

[mknauss]

When you test pH, it is before you add liquid chlorine for the day, correct?

 

[noturbizniss]

How old is your plaster?

What is the pH and TA of your fill water?

It is normal to need to lower pH in some plaster pools once or twice a week. Try and leave your pH at 7.8. No reason to lower it more. pH of 7.4 - 7.6 rises more rapidly.

thanks. The plaster is likely 30 years old or more

When you test pH, it is before you add liquid chlorine for the day, correct?

Ummmm. Today I added chlorine at a out 2 pm and tested at 7pm. Is that too close to the add time?

 

[mknauss]

It is best to take your water sample, do the FC test and any other (such as pH) tests, then add chemicals.

I would wait until tomorrow and do that process to see what the pH shows.

You mention hard water, but your TA is very controlled. As Allen asked, what is the TA and pH of the fill water?

 

[ajw22]

Target a pH of 7.8.

Let your TA drop to 60 or 50 naturally as you adjust pH.

With pH target of 7.8 and TA 50-60 I need to lower my pH from 8-8.2 about once a week.

 

[noturbizniss]

Fill water ph is 8ish (maybe a drop higher, but less than current pool ph reading, i.e. Not as deep a red on the Taylor test) and the TA is 120

 

[ajw22]

That fill water is part of your problem. It will constantly drive your pH up.

 

[mknauss]

Fill water ph is 8ish (maybe a drop higher, but less than current pool ph reading, i.e. Not as deep a red on the Taylor test) and the TA is 120

Thanks -- you know that will push pH up when used, and raise your TA which also forces pH up.

 

[noturbizniss]

Got it. So I'm basically stuck and simply have to add MA whenever I fill? What can I use to drop TA? What's my target TA?

 

[mknauss]

Your TA of 70 is good. Adding acid to control pH is part of managing water chemistry.

 

[ajw22]

Don’t touch TA. Just manage pH to 7.8. Needing to adjust pH is part of your natural pool environment.

 

[noturbizniss]

Update
It rained a lot last Monday and Tuesday so I tested after ph was 8.2 again. I added MA and it dropped to 7.6. I just tested again now after 4 days and it's again 8.2
We had no rain since and I added no water manually.
Is my TA of 70 too low for manually chlorinated? What else could be causing the swings?

 

[ajw22]

Needing to lower pH every 4 days is normal for some pools.

 

[Lilypad]

Any aeration of the water will cause PH to rise. Do you have water features running? Kids or dogs splashing around? Are your returns aimed up and breaking the surface? I add MA about once or twice a week.

 

[noturbizniss]

I do have a spa attached that is raised up and waterfalls into the pool. That could do it?

 

[ajw22]

I do have a spa attached that is raised up and waterfalls into the pool. That could do it?

Many of us have turned off full time running of the spillover and use our automation to run the spillover briefly a few times a day.

Spillover creates aeration that causes pH to rise.

 

[noturbizniss]

Many of us have turned off full time running of the spillover and use our automation to run the spillover briefly a few times a day.

Spillover creates aeration that causes pH to rise.

I don't have any kind of automation. The system is probably 30 years old with manual valves to direct the return.

 

[ajw22]

That setup plus your fill water chemistry says it will be normal for you to be lowering your pH regularly.