Shocked last night....FC fine....big PH increase


LifeTime Supporter
Sep 10, 2007
Gloucester County, NJ
Before shocking the pool with 12.5% liquid chlorine, I had the following numbers:

FC .5
CC 1
PH 7.2
TA 70
CH 210
CYA 40

I put in enough chlorine to take the FC level to 15, based on Jason's Poolcalculator. This morning, my levels are:

FC 15
CC 0
PH 8 <<-- This is where my question lies
TA 70
CH 210
CYA 40

So, as you see, the FC level appears to have held overnight, which I wasn't expecting. However, my PH level shot through the roof. I had put in muriatic acid to bring down the PH as the PH was really high when I opened the pool. I expected it to drift upward, but between yesterday evening and this morning it increased dramatically. I don't want to just add more acid as I know that will also reduce my TA. I also don't want to just add baking soda to raise the TA as that will also raise the PH. What's the best approach here?


TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
Silver Spring, MD
Don't worry about the PH while the FC level is very high. Wait till FC is back down to 10 or below and then test the PH again. High FC levels will cause the PH to read higher than it really is.