Calcium hardness

H-12 1/2 Mike

Bronze Supporter
LifeTime Supporter
Apr 14, 2014
Highland Village, TX
What causes the calcium hardness levels to deplete as the water temperature goes down?
Chlorine = 8.0
Ph = 7.6
Total Alkalinity = 140
Calcium hardness = 190 (last week it was 210 and I added 4 lbs of calcium chloride).
CYA = 50
Temperature = 51 (pool - last week it was 61)
Pool is 16,400 gals. Gunite.


Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
In The Industry
Apr 1, 2007
Sebring, Florida
I am not aware that temp has any affect on on CH.

I will mention that the difference of 20 ppm is not very significant on CH.

The current instructions in the TF-100 suggest a 10 ml pool sample giving each drop of R-0012 a value of 25 ppm instead of 10 ppm value you used. 25 ppm accuracy is just fine for our purposes.


Well-known member
Jul 25, 2012
Central Texas
Has your portion of Texas experienced significant rain? That could account for some depletion. Mine has dropped 40 ppm over the last 2 weeks from rain and flow out.