What are the lower limits for TA?

[austinnichols101]

I've successfully gone through the process of lowering my TA from 110 down to 80. Once I was done I waited a week and saw that the pH was up by about .2 so I added just over a cup of 31.45% acid for my 18,000 gallon in-ground. I am quite pleased in the reduction in acid usage.

Now I'm wondering if I should consider going lower and if so if there is a lower boundary that I should watch out for. I'm perfectly OK with adding a cup a week so this is really for my own knowledge more than anything.

FC 5
CC 0
TC 5
PH 7.6
TA 80
CH 290
CYA 50
Borate 50
Temp 88! (I'm already going to have to start using the solar panels at night to cool things off a bit.)

 

[chem geek]

If you generally keep your pH at 7.6, then you could lower the TA down to 60-65 which would give a saturation index of around -0.2 which is fine.

There is no real lower limit for the TA except 23 ppm which would mean no carbonates in the water at all (something definitely NOT to do; the TA is just from the CYA in that case). Generally speaking, we don't recommend going below 50 ppm just so you always have some sort of reasonable pH buffering. At that low TA, one should have a higher CH and/or pH to compensate.

This thread on The Pool Forum talks about a user who got his TA to 40 and was very happy with the very low rate of pH rise.

Richard