High TA

[bdearen]

Hello,

I moved into a house about 3 months ago with a 20k gallon inground plaster pool that was build in 2006. The previous owners used the same pool guy for the last 10+ years. He only ever uses pucks and powder shock. I asked him about the CYA and he said it's an old myth that doesn't matter. The pool is spotless and has always looked great since we have been using it. I cancelled the pool service a few weeks ago and started maintaining it myself. I had a pool at my old house and figured it wouldn't be too bad. I ordered some additional reagents for my Taylor test kit and as I guessed, the CYA is so high I can't even measure it. I was hoping to let it dilute out over the winter and not have to drain any of the water. When I first tested the water I had FC 0, PH 7.6, TA 170. I added about 90oz of 12.5% liquid chlorine, then slowly added about 60oz of 34.5% muriatic acid a few hours later. I diluted the acid with pool water in a bucket and added about 20oz at a time over about 30 minutes.

I went out to test the pool this afternoon, so about 6 hours after I added chemicals. The FC went up to 5.0 as expected, the PH went down to 7.4 as I also expected, however the TA actually went up from 170 > 180, where I would have estimated it went down to 150 or 160 based on the dosage of Muriatic Acid.

I am looking for some help here... Do I dose again with Muriatic Acid tomorrow? I have read that the maximum single daily dosage for acid is 90oz, is this accurate?

Current Levels
PH - 7.4
FC - 5.0
TA - 180

 

[Jimrahbe]

B,

First.. TA is the last thing you ever need to worry about, so I would not get too carried away with it..

Second.. It takes me two days to reduce my TA from say 120 or so, to about 50 ppm... The first few times I dose with Acid there is not much noticeable change.. Or if there is a change, it does not last very long. I keep testing and dosing over and over and over every 2 to 4 hours.. Eventually, TA starts to move in bigger increments..

I run aeriation to driver the pH back up constantly.. I start by lowering my pH to 7.1 or .2... Then wait until the pH comes up to about 7.5 or 7.6 and do it all over again.

Every pool is different, but I find that my pH is pretty stable when I have a TA between 40 and 50 ppm.

I have never heard of the "maximum single daily dosage for acid is 90oz"..

Thanks,

Jim R.

 

[bdearen]

Thank you for the info.. Why do you say TA is the last thing I should worry about? I am guessing you are thinking I need to reduce the CYA first which means drain 50% of the pool?

 

[Jimrahbe]

B,

No, TA just does not have a great impact other then pushing pH up.. If you can keep pH under control with MA, then TA just does not matter all that much.

If you ranked all the chemical tests in the order of importance, TA would be last.

That said, you do need to keep your FC and CYA in balance per this chart.. FC/CYA Levels

An FC of only 5 ppm with a very high CYA is not where I'd want to be.

Thanks,

Jim R.

 

[bdearen]

B,

No, TA just does not have a great impact other then pushing pH up.. If you can keep pH under control with MA, then TA just does not matter all that much.

If you ranked all the chemical tests in the order of importance, TA would be last.

That said, you do need to keep your FC and CYA in balance per this chart.. FC/CYA Levels

An FC of only 5 ppm with a very high CYA is not where I'd want to be.

Thanks,

Jim R.

Thank you again for the info. I was under the impression TA higher than 120 could cause issues with plaster and equipment. I guess I was wrong. I will work on draining 1/2 the water this weekend.

 

[wireform]

All the above and I don't have much to add. The TA didn't go up it's most likely testing error but little difference does it make.