Adding acid to fight pH rise -- is TA getting too low?

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lalittle

Well-known member
Apr 4, 2011
184
Los Angeles, CA
I have a non-SWG pool, about 22K gallons, which uses liquid Cl.

I've never been able to figure out why my pH rises so much -- about 0.2 per day -- but I add muriatic acid a couple times a week to push it back down. I generally let it rise to 7.8-ish and then knock it back down to 7.2. The rise has gotten a bit worse recently since I stopped using pucks (which are acidic) and started using only liquid Cl. I'm wondering how much of a problem it is that all the acid additions are dropping my TA. It's about 50 right now, but I believe it will continue to drop. I tried raising it with baking soda, but as predicted, it just dropped down again over time. Just how low would be "too low" for the TA? Based on my reading, a lot of people would already say it's too low, but it won't stay higher without a constantly adding baking soda. What is the lower limit below which I should not let my pH drop?

I also read that with a low enough TA, CO2 outgassing shouldn't happen as much. Is this true? If so, how low of a TA would indicate that the pH rise is NOT due to outgassing?

I have not tried borates yet. I'm considering this, but I'm not yet clear that this will substantially effect the pH rise, and I'd rather not use borates if possible since I have a dog.

My numbers as of this writing:

FC - 7.5
CC - negligible
pH - 7.6
TA - 50
CH - 825
CYA - 60
Salt - 1800

Thanks,

Larry
 
Please add your location (City, State or City, Country) to your profile and pool details to your signature and as described HERE as it will help us help you in the future. You would think after being here for 3.5 years, someone would have asked for this into by now ;)

Do you have a lot of water features or source of aeration?
It is odd that you pH would be rising that fast with the low TA and no SWG.
Have you tested your top off water? Maybe it is really high pH?

I am not sure I would raise the TA, but I am not sure how low is too low. I would not think you would want to be much if any below 50ppm.
 
No water features, but I do have a "Pool Skim" which is a venturi skimmer that attaches to a return jet. Fill water is high pH, but this is not the issue because the pH rises even when I don't add any water.

I'll change my signature later, but it's an in ground, plaster pool, Pentair VS pump, Quad 100 filter (DE). I live in the Los Angeles CA area.

It's notable that my next-door neighbor does not appear to have any pH rise.

Larry
 
pooladdict said:
Any suction side leaks in pumps? Any visible bubbles in returns? Do you see any bubbles being formed by pool skim as the water vortexes down into your skimmer? Your Ch seems really high at 800+
Click to expand...

I do see some bubbles in the check valve right before the pump, as well as in the pump basket window. I also see some fine bubbles at one or two of the returns. I have not been able to determine, however, where they're coming from. The entire system was leak tested a little while back and I was told that I did not have any leaks. This would mean that the bubbles were coming from somewhere else, like the Kreepy Krauly hose, but I'm honestly not sure where to look given that the tests came back negative. I may have to do another leak test with someone else.

Regarding the Calcium Hardness; yes, it is high, but it was substantially higher (1200 perhaps) before a couple drains/refills over the summer. I got it "down" to 825, but I didn't want to have to pay for more water at that point. I read that some people run their CH above 1000, so I figured that 825 was low enough, at least for the time being.

That said, can high CH can lead to pH rise?

Thanks,

Larry
 
If you suspect your Kreepy Krauly hose, have you removed all your Kreepy Krauley hose and hardware (including any vacuum regulator and skimmer adaptor plates) and seen if the bubbles at the returns are reduced?

Is your water level high enough that there's no excessive turbulence in your skimmer?

Suggest you read the Suction Side Leaks article in Pool School.
 
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