Why is my CH so high?


Jun 9, 2015
Corpus Christi, TX
Any help is appreciated as I’m at my wits end. We have a roughly 6 month old gunite pool. I’ll list all my parameters below, but my issue is CH. It was all the way up to 775 so I decided to go ahead and do a partial drain and refill with our tap water that consistently tests right at 300. I drained about 60-70% and according to the TFP calculator that should’ve brought it down to less than 500. I finished the refill yesterday morning, ran the pool, added 120lbs of salt, and then tested today. After all that my CH level dropped from 775 to 675. How did I only lower it 100ppm? Where is the calcium coming from if it’s not already in my tap water? I’m confused, frustrated, and a little angry right now since I just ran my water bill up about 6000 gallons for basically no reason. Can someone help me understand what the heck is going on here?

~9000 gallon gunite saltwater pool,
tested w/TF-100
Levels on 11/15
CC -0.5
CYA - 60
TA - 110
Tap water CH 300
CH level on 11/21 675


Mod Squad
LifeTime Supporter
Jan 17, 2012
Evans, Georgia
I don't see a pH listed?
Are you using 10cc or 25cc for the Calcium Hardness test?- what are you multiplying your result by?
Are you using the Speed Stir device??
Maddie :flower:


Jun 9, 2015
Corpus Christi, TX
Sorry, I left that out somehow. My pH is currently 7.2. It climbs pretty rapidly though. I’m hoping that changes as the pool ages. I also have boric acid coming from dudadiesel which might help slow my pH climbing so fast. I’m multiplying the # of drops by 25 using a 10mL sample. No speed stir, just swirling. BUT....here’s an interesting twist: I just took a sample to Leslie’s to have them test it. Their machine says my CH is 300. Now I’m not sure what to believe. I know I’m doing the test correctly as per the instructions. I think tomorrow I’ll take another sample to a different store to see if they get the same results.


Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
In The Industry
Apr 1, 2007
Sebring, Florida
Then if you are doing the CH test correctly, your CH is 775 not 300. Always trust your testing over any pool store.

Only a guess as to why the CH didn't go down like you want but we see a LOT of folks do partial drains and don't accomplish the percentage drain they intend.

Regardless, if you want your CH lower, you'll have to replace some more water. A newer pool like yours still throws off some calcium. You may face this battle a while more.

I would suggest you focus more on careful pH management. 300 CH fill water is problematic and you will have this issue again......sooner than you want.


Silver Supporter
Bronze Supporter
Nov 12, 2016
Plano, Texas
Highly recommend that you get a SpeedStir. I found my testing for CH varied quite a bit when using the swirling technique. With the SpeedStir you remove the human factor with the exception of miscounting drops or squeezing the bottle vs. the preferred method of letting the drop form on the tip and release. It gives you a much higher accuracy of your levels when you do all the testing yourself. Same person, same equipment/reagents etc. Going to a pool store will only add more confusion and frustration. Trust your testing. Let us know how you’re doing.
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