High TA & PH Rise

[Hwmeador]

So I'm new to the crew here and probably been onboard with the TFP method for probably 1 month. For the last 4 weeks the only thing I had added to my pool has been liquid chlorine to maintain the correct FC ratio and then sodium bisulfate to bring down the PH. The Ph tends to creep up and normally sits around 7.8 on my pool. My TA is high which doesn't help. Yesterday I finally got my hands on some Muriatic Acid and switched to that to bring Ph and TA down. I added about 1/3 of a gallon and Ph dropped within the hour from 8 to 7.6. This morning I check and the Ph is already back up to 7.8 and the TA didn't seem to move much. My TA is 190. So today I added about another 1/3 of a gallon of the muriatic acid.

My question is do I just keep adding muriatic acid to drive the Ph and TA down? I added the amount that pool math suggested but clearly didn't get the response I was expecting. When testing this morning I didn't really see much reduction of TA. What kind of timing should I expect on continuing to drive and get my Ph and Ta down? I am in North Texas and the head and humidity has been very high, so the pool has been adding makeup water.

 

[mknauss]

The TA is being reduced when you add acid. It is countered by any fill water with TA you are adding plus the testing range of accuracy.

Keep the pH in the 7's. The TA will reduce. You may need to check pH every few days.

 

[Hwmeador]

How much muriatic acid is too much? In the last two days I have used a full gallon of muriatic acid. My pH is like 7.8 , I add acid and it comes down, then the next day we are back at 7.8. A week ago I tested TA and it was like 170, so I know it is high and have been trying to bring it down.

Sequence of events:
Test for TA 7/16/22 (170)
Add 1/2 gallon of muriatic acid 7/16/22 - I could see the pH drop
Add another 1/2 gallon of muriatic acid 7/17/22 - again, pH drop
7/19/22 partial drain and refill working to bring CYA in, I probably drained about 1 ft about of my pool
Over the next few days I used a 2nd gallon of muriatic acid to keep trying to keep the pH down and reduce TA (i understand that this was likely thrown off by by doing a partial drain, I have not tested my fill water but I am on a well and water runs through a softener).

Add 1/2 gal of muriatic acid 7/23/22
Add 1/2 gal of muriatic acid 7/24/22 ( pH prior to acid was 7.8)

Just trying to get a measure, the effectiveness long terms seems to be minimal. I'm assuming I need to to test TA again, but either way it seems like I am using lots of MA in order to keep trying to bring it down.

 

[mknauss]

(i understand that this was likely thrown off by by doing a partial drain, I have not tested my fill water but I am on a well and water runs through a softener).

Test the fill water TA -- the softener does not effect the TA

Test your pH. When it rises to 8, lower it to 7.4. Test TA once or twice a week as you need the data for Poolmath.

 

[Hwmeador]

Ok! So I just tested my fill water. Looks like my fill water TA is 250. Yikes.

So is my only option to keep hammering away with the MA hoping to bring down the TA in the pool and then be able to compensate for the autofill makeup water from evaporation with smaller amounts of MA? This still leaves me with my original question of how much MA is too much.

 

[mknauss]

You will need to always add MA to counter act the high TA of your fill water.

You use as much MA as you need. Not sure what you mean by too much.

 

[Hwmeador]

Does the 3 gallons that I have used over the last 8 days seem excessive?

 

[mknauss]

Not if your pH has risen and you used it to lower the pH and TA.

You have a large volume pool. At an elevated TA, the pH rises quickly.

 

[Toxophilite]

If it got the job done, it's not excessive. It's just what it needed at the time. When I started high TA with my fill water at 260 TA, I can't remember the exact dosing but it was in gallons over days, as TA lowered from my dosing with acid to manage pH and aeration, over time that was maybe half that amount needed. Now, my TA is around 80 and manageable, but due to my fill water I need 28oz every 3 days to stay in mid-7's pH, like clockwork. That will change as evaporation level changes in the Fall, I'm sure. But, the big takeaway is to manage your pH and TA will come down and your acid demand should lessen.

 

[proavia]

As long as the quantity you are adding is keeping the pH in the 7's you're good. You may have to add frequently to help keep the TA in check. Just never add more at any one time than required to get the pH to 7.2

 

[Hwmeador]

Update: Ph is down in general. Normally my daily check I have been getting 7.5-7.6. The quantity of MA that I have been using has decreased and Ph has stayed in range. The last TA check I did was 100, so it is coming down!

Thanks for the feedback.