CH Keeps Dropping, pH Rises

ToddInGA

Member
Jan 31, 2020
9
Valdosta, GA
My pool is behaving pretty well this year (only 2nd season we've owned this home and the pool), but two tests seem to change every week. pH keeps rising (have to add ~1/2 gallon about 3 weeks of the month) and CH keeps dropping (added 25# two times in the past three weeks). Am I missing something, or is this just an ongoing battle?

25,000 gallon gunite pool with an SWG. Attempting to maintain pH 7.2-7.8 and CH at 350-450.

2/21
FC - 8.5
pH - 8.0
TA - 70
CH - 300
CYA - 80
Salt - 3600
Temp - 59*
Added 25# of calcium chloride and 2 quarts of 31.45% Muriatic Acid

2/29
FC - 6.0 (adjusted salt cell down)
pH - 7.8
TA - 70
CH - 320
CYA - 80
Salt - 3700
Temp - 56*
Added 25# of calcium chloride and 2 quarts of 31.45% Muriatic Acid

3/6
FC - 6.0
pH - 7.6
TA - 60
CH - 325
CYA - 80
Salt - 3600
Temp - 60*
Added another 25# of calcium chloride

I'm adding more calcium chloride than Pool Math tells me to, but still not getting into target range, let alone actual target of 400.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
21,239
Northern NJ
Pool Size
35000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
Do you have an autofill on your pool?

What is the pH, TA and CH of your fill water?
 

YippeeSkippy

Mod Squad
LifeTime Supporter
Jan 17, 2012
14,963
Evans, Georgia
Here in Georgia we've had a *mess* of rain this season..... have you had to drain water from the pool lest it get too high? I would imagine it may be the problem?

Your spillover if being used is causing the pH rise, as well as if its a new plaster pool the pH rises as the plaster cures. It should calm down over time.

How are you testing> Which kit??
Maddie :flower:
 
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ToddInGA

Member
Jan 31, 2020
9
Valdosta, GA
I do have autofill on the pool. Haven't tested that water supply for levels, but it is softened water. I doubt that is factoring into it right now though, because as YippeeSkippy said, we've had a lot of rainfall over the past few weeks.

It has an overflow, so I don't drain anything manually. Rain water is probably the right answer, and I wasn't thinking about that. It's a 19 year old plaster pool, we've just owned it for 1 year (Hopefully within the next year that plaster surface will become a Pebbletec surface). Dumb question, but how does the spillover spa cause a pH rise?
 

ToddInGA

Member
Jan 31, 2020
9
Valdosta, GA
So I'm still adding 25# of CaCl every 1-2 weeks trying to get it to the 350-450 range, and never get it above 325. While I do have an autofill that will fill with softened water, I don't think I have a leak because neither my salt nor CYA levels are dropping. Like I said before, it isn't a new pool surface, so there shouldn't be any interaction there. I'm using Taylor chemicals for the testing, purchased fresh this year. Any more thoughts, or anything that I should really be concerned with? My latest readings (3/28) are below.

FC - 3.5
pH - 7.4
TA - 65
CH - 325
CYA - 75
Salt - 3850
Temp - 74*

Even more strange, I tested CH the previous day and it was 325, so I added 25# of CaCl. No change in readings. I'm confused.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
33,918
Laughlin, NV
If you add calcium, it is in the pool water. So if by calculation you have added enough calcium, stop. Monitor for several weeks and see what the results are.