Sudden Spike in pH, TA, and CYA

ghall6292

Bronze Supporter
Jun 10, 2018
72
North Central PA
I have been preparing my pool for closing over the past 10 days. I have monitored chlorine and pH every day. I am filtering 12 hours a day, as normal. My pool temp has gone from 85 degrees down to 53 degrees today. Several nights with temps in the high 20's to low 30's have helped.

Today, I did a complete set of tests, in preparing to close. To my surprise, my pH was at 8.2, well above the normal 7.4-7.6. My TA was now 140, up from the normal 110-120 (manually dosed pool.) My CYA had also risen from 40 to 50. CC's were normal at zero. CH was normal at 150 (vinyl pool.)

We have not had rain for ten days, and I have not added any chems except chlorine. Also, I have not added any fill water. Any idea what's going on?

Thanks,
G.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
21,199
Northern NJ
Pool Size
35000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
What is your FC?

Did you let the pool water warm to room temperature before the CYA test?

20 ppm difference in TA is no big deal and could just be testing errors of 2 drops.
 

ghall6292

Bronze Supporter
Jun 10, 2018
72
North Central PA
Thanks for your quick response. This is my first year on bleach after a spring Baquacil conversion. All has gone swimmingly :confused: until now.

I actually did not let the water warm to room temp for the CYA test. Didn't remember reading that. I'll give it a shot. What about the pH spike? Is this simply related to the higher TA? Should I now use acid to get pH (and the TA) down?

Just wondering... is any or all of this related to the much colder water I now have (53 now vs 84 degrees?)
 

ghall6292

Bronze Supporter
Jun 10, 2018
72
North Central PA
6.0 FC. Pool Math says to run my FC at 4 ppm. I usually run it closer to 5-5.5 ppm in case I miss a day or forget until after dark. I make my target in Pool Math 7.0 and let it drift down to 5.5 by the next day. Too high???
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
21,199
Northern NJ
Pool Size
35000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
Your FC level is fine. I was checking it was below 10 and not affecting the pH test.

I would believe the pH test and add acid to lower it.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
21,199
Northern NJ
Pool Size
35000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
Tthe CYA test is affected by cold water temperatures. The actual chemical targets don’t change due to cold water.