FAC raising after acid addition

LTPOrangePool

Well-known member
Feb 21, 2019
46
Port Orange, FL
Is that thing? This morning I tested FAC at 10 and dropping coming down from a shock. PH at 7.7. I followed pool math to drop ph and TA, and added 3 qts of MA. I tested about an hour later and now my ph is at 7.2, and chlorine seems like it is back to 11. Is that the nature of the beast when ph is moved around?
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Something doesn't seem to be adding up when I enter some numbers into PoolMath. For example, if your pH was 7.7, adding 3 "quarts" would lower the pH to about 6.6. Can you confirm which % strength muriatic acid you are using? (i.e. 31.45%)? Also, did you mean to say quarts?

As for Free Chlorine, muriatic acid would not increase FC. Either there is a testing disparity or something else is happening.

Can you also clarify your current CH, TA, pH, and water temp please?
 

LTPOrangePool

Well-known member
Feb 21, 2019
46
Port Orange, FL
Wow, I hope not. I just doublechecked. When I plug in 7.7 to 7.0 at 170 alkalinity, it gives me 98 oz to reach 7.0 ph in 16000 gal. The capacity is probably the disparity. In any case, it didn't get below 7.2. I didn't know what was going on with the chlorine reading either, and I tested it twice, same result. It has been dropping daily by about 3 ppm. I didn't know if one level effected the other reading. Acid has been my only addition. I will retest everything in a couple hours for a snapshot and post.
 

LTPOrangePool

Well-known member
Feb 21, 2019
46
Port Orange, FL
At nine tonight:
FAC- 10, maybe 9.5, I thought it would be down to about 7 after the day and swimmers.
PH- 7.4
CH- 250, no change there
TA- 150, slight decrease from yesterday; some swimming, but have not done any aeration yet
CYA- 60
Temp- 80F
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
21,989
Laughlin, NV
CH will not change unless you add calcium or remove water. So no need to test that very often.

The TA drops when you add acid. Aeration raises your pH. No effect on TA.