Ph and Alkalinity continuing to drift up

[jimcam22]

I am having a problem with my ph and alkalinity continuing to drift up. Every time I lower the ph to 7.5 it just jumps back up to 8.2 or higher (can't tell higher from the kit) and the alkalinity drifts up with it. I got them both down to 7.5 and 90 respectively but they went right back up. Any ideas about what could be causing this and what I can do about it. I use liquid chlorine. We have had the pool for five years and this is the first time I have had this problem.

My numbers are
FC: 4
CC: 0
TC: 4
ph: 8.2 (or higher)
TA: 120
CH: 110
CYA: 50
Temp: 79
Pool is 18,000 gallons, vinyl.

 

[duraleigh]

it just jumps back up to 8.2 or higher

How long does that take?

 

[JohnT]

That's pretty normal. You need to follow the Lowering Total Alkalinity

process in Pool School to get the TA down to a point where the pH stabilizes.

 

[jimcam22]

It takes less than a week for it to drift back up. Using the Lowering Total Alkalinity process is going to be my next step but before I do that I thought I would ask if anyone could think of a reason that it is not stabilizing. The last time I went through the process and got it down to ph 7.5 and TA 90, which I thought was in range, it just went right back up. What would be the the number to shoot for to stabilize the alkalinity.

 

[pwrstrk]

I wouldn't go any lower than 70. See what happens at 80. Could be the nature of the beast. If your adding acid once a week that's not over the top. ?

 

[JamesW]

The pH can drift up from carbon dioxide off gassing. However, for the TA to rise, something basic has to be added. It could be from fill water if you're adding a lot and the fill water has a high TA. The other possibility is that the liquid chlorine has a lot of excess sodium hydroxide.

What is your fill water TA?

 

[annaj]

We drained our pool last summer for painting and our fill water is very high in alkalinity, of course alkalinity anchors your PH, so our PH was very high as well. Our alkalinity was 320 ppm and our PH was off the charts. It was a chore and took about four weeks to balance it all out again, but with adding 2 gallons of acid twice a week, constantly testing we have our PH at 7.6 and our TA at 120. It could also be that your chlorine has a lot of sodium hydroxide like the above post stated. What test kit are you using?