Alkalinity and Ph Questions

[holdup1time]

My pool has been up and running now for almost a month. I have been using Triclor 3" tabs but before the tomato throwing begins, I started yesterday switching to liquid chlorine.

I know the Triclor pucks are very acidic.

My question is:

After almost a month, I did notice a continued trend down in my TA readings which I attributed to the low PH Triclor pucks....but why does my Ph always slowly creep up and not down like the TA?

I have not been using my water features as aeration will increase Ph and mine is always on a slow climb up.

My pool is new plaster of almost a month now.

All my samples have been in good range since opening my pool

Currently,
FC 7
CC 0
Ph 7.6
TA 90
CYA 70
CH 190

My pool is looking great so this is more of a learning question as to why Ph has not gone down with the low acidity of the triclor pucks?

Thanks!

 

[mknauss]

New plaster. The pH will rise for up to a year. Your TA is falling as you have been adding acid with the trichlor. Once your TA gets to 70 or so the pH rise will lessen, but not stop due the new plaster.

Only lower your pH from 8 to 7.6 with acid. Your CH is on the edge of low. Are you tracking CSI?

 

[JamesW]

As long as the TA is kept high enough, the pH can't go too low because carbon dioxide offgasses and raises the pH back up.

 

[holdup1time]

New plaster. The pH will rise for up to a year. Your TA is falling as you have been adding acid with the trichlor. Once your TA gets to 70 or so the pH rise will lessen, but not stop due the new plaster.

Only lower your pH from 8 to 7.6 with acid. Your CH is on the edge of low. Are you tracking CSI?

mknauss,

Ok so mainly sounds like a new plaster issue.

That is exactly what I do...wait till Ph hits 8.0, then add 30 oz of M.A. and that brings me down to 7.6 for my size pool.

CSI - yes the pool math app tracks that automatically for me when I enter in my test results....I've always been between (-0.3 and +0.3) Believe the app has range of (-0.6 and +0.6)

Regarding the CH - My water was initially 170...I was following the National Plaster Council Assocations 28 day start up plan which stated I should not have my CH greater than 200 in that first 28 days...not really sure why but luckily my water naturally was around 170. About 10 days into opening my pool, we went on vacation for 6 days and was not switched over to liq chlorine yet. So I added 2 lbs of shock which was Cal Hypo and my friend came over and added 2 more later that week. Had I been home, I would not have added the shock since that raises the CH...but we do what we can and I'm still learning.

 

[holdup1time]

As long as the TA is kept high enough, the pH can't go too low because carbon dioxide offgasses and raises the pH back up.

Thank you James for the chemistry lesson