Low TA levels

[bcinsd]

I have a 15k gallon inground pool with variable speed pump, IC40, and acid injection. I live in San Diego where tap water hardness is very high. My pool chemistries are thus:
Hardness 500
Ph 7.6
FC 3
TC 3
CYA ~50
TA < 40

I've tried to correct the low TA in past by adding calculated amount of appropriate bicarb, but this just raises the pH and then when the acid injection completes to get pH back to 7.6, TA falls back down to below 40.

What am I missing here?

 

[Teald024]

What is your main reason for increasing TA? What level are you trying to get your TA to? If you use bicarb to get to TA of 60, pH should shouldn't go up too much. Also, try adjusting so that the pH is maintained at 7.8 instead of 7.6. See if this helps you use less acid which will help control TA drop.

 

[bcinsd]

What is your main reason for increasing TA? What level are you trying to get your TA to? If you use bicarb to get to TA of 60, pH should shouldn't go up too much. Also, try adjusting so that the pH is maintained at 7.8 instead of 7.6. See if this helps you use less acid which will help control TA drop.

Just trying to achieve recommended levels. Level should be around 50, no? Mine is below 40 (how much below, I don't know). Don't know if this is important. I appreciate your input.