How long to lower TA?

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T

tobydog

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May 15, 2016
34
Central Valley/ CA
Apparently I let my water get out of hand this winter. I tested the other day and came up with:

FC 1.0
PH 8.2
TA 140
CH 550
CYA 50

Not surprising, I now have some scaling at the water line.

Since then, I've gotten the PH and FC in check. I'm working on the TA with acid and aeration, but I'm curious how long it should take. The pool is about 25k gallons.

Any thoughts?
 
toby,

I have a 17K pool and it takes me about two days, testing and adding MA every 3 or 4 hours to get from about 125 down to just under 60... I leave aeration on overnight but quit checking and adding about 10 pm and then start again the next morning...

Why does your signature say your pool is over 35K???

I'd also be looking at your FC as 1 ppm is way below the very, absolute, minimum to prevent algae...

Thanks for posting,

Jim R.
 
Jimrahbe said:
toby,

I have a 17K pool and it takes me about two days, testing and adding MA every 3 or 4 hours to get from about 125 down to just under 60... I leave aeration on overnight but quit checking and adding about 10 pm and then start again the next morning...

Jim R.
Click to expand...

Jim, is there a temperature effect to this cycle? That is, does it take significantly longer if the water is 50 degrees versus 80 degrees?
 
UPDATE

So far, the TA has come down to 110. I've been adding acid when the ph gets to 7.5, bringing it down to 7.2. I have been running the pump with the return open for the 3' sheer descent for about 10 hours everyday. I noticed after not checking the ph or adding MA for two days, the ph only rose to 7.5. Does that sound normal? Is the sheer "waterfall" enough aeration?
 
Yea, that's why I asked about temperature effects. I was looking for anecdotal evidence.

My pH is taking much longer to push up than it did last summer, even with the aeration devices running (sheer descents, spillover, floor system). I'm pretty sure the 50 degree water is a big factor in the slower pH push, because my other 2 pH-rise factors are:

* SWCG, which is off for the winter and not contributing to push the pH up at all
* newish plaster, which is now 8 months old, so probably not contributing at the rate it was several months ago

I have ChemGeek's CO2 out-of-equilibrium chart bookmarked because I really like the concept it presents:

https://www.troublefreepool.com/~richardfalk/pool/CO2.htm

This chart assumes 80 degree water. I haven't found the formula to see if temperature effects are linear, or more than or less than linear.

But as the other guys say, one reason we like cold soda and cold beer is because the bubbles stay longer!
 

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Inserting myself to ask my own question... what is the mechanic that actually reduces TA? Is it the adding of the acid, or is it the rise in pH that consumes TA?

Edit: Disregard, says it right here in the ole trusty dusty Pool School:

"It is actually the acid which lowers TA. Adding acid lowers both the PH and the TA. Then aeration raises the PH without changing TA. Do not use chemicals to raise your pH during this procedure (unless your pH accidentally goes way too low); that will just raise your TA back up, which is exactly what you are trying to avoid."
 
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