TA - How low is too low?

[Crimson]

My TA has been steadily dropping since my pool was replastered and my PH rises regularly. Its now down to 70. My pool is inground concrete. Numbers are as follows:

FC: 4.0
CC: 0
PH: 7.7
TA: 70
CH: 230
CYA: 40

When should I add some baking soda? Should I leave it for now and start raising if it drops even further (Which I suspect it will as I need to regularly add acid.)

 

[Casey]

I believe that you are on the border of being low but maybe not dangerously low yet. I would keep an eye on it so it doesn't go lower and perhaps bump it up soon.

Your pH rise is definately because of the re-plaster job and should level out over time, within the next year.

 

[Guest]

What are you chlorinating with? If you are using trichlor or dichlor then your TA is too low, bring it up to about 100-120 ppm.
If you are using bleach, liquid chlorine, cal hypo, or lithium hypo then your TA is perfect but you shoulod bring up your calcium hardness to about 300 ppm.

Also, how long ago did you replaster? If it's been less than a year then once the TA drops below 60 ppm bring it back up to 80 but not higher so it does not add to the acid demand from the new plaster.

 

[Crimson]

Replastered about 3 months ago.. Using liquid 10.5% chlorine..

 

[Guest]

Your pH is rising because the curing plaster is leaching alkaline material into the water. Keep your TA between 60-80 until the acid demend drops otherwise the higher TA will also add to the acid demand. If your CYA levels are not a problem it is often adventgeous to use trichlor with new plster since it helps to maintain the pH but do keep a close eye on your TA in any case. Since your current CYA is 40 ppm I would use trichlor until the CYA is around 60-70 ppm then drain some water to bring back down below 50 ppm. Your plaster will be a bit more cured by then and the acid demand a bit less.