Sudden Spike in pH, TA, and CYA

[ghall6292]

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]

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]

Thanks for your quick response. This is my first year on bleach after a spring Baquacil conversion. All has gone swimmingly 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?)

 

[ajw22]

CYA Testing - Further Reading

www.troublefreepool.com

I would not worry about the TA.

What is your FC level?

 

[ghall6292]

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]

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.

 

[ghall6292]

That is my plan... now. LOL

Then the drop in temp has no discernible effect on pH/TA nor CYA?

 

[ajw22]

Tthe CYA test is affected by cold water temperatures. The actual chemical targets don’t change due to cold water.