low alkalinity

[poppii]

hi,

had my water tested and the alkalinity was 70, ph 7.4. i was told to add some bi-carb to increase the alkalinity, but my question is if I do that wouldn't i increase the pH as well, and then have to add in acid to lower the pH and hence lower the alkalinity again? so all is done is in vain.

[chem geek]

If your pH is stable, you don't need to raise the TA. 70 ppm is fine. If the saturation index is too negative, then you can increase Calcium Hardness (CH) to compensate (if you have a plaster or fiberglass pool; vinyl doesn't need the saturation of calcium carbonate). You can use The Pool Calculator to calculate the saturation index.

[swimfit]

Alkalinity ideally can be 80-100 ppm. The safest chemical you could use is sodium bicarbonate for the purpose of increasing alkalinity. The ratio you could follow is not more than 10 lbs for every 10,000 gallons of water.

[czechmate]

[quote="chem geek"]If your pH is stable, you don't need to raise the TA. 70 ppm is fine.
That may not be enough if your CYA is at 100.
Don't you need to subtract 1/3 of CYA from TA value to get CSI calculation more correc, or you do not subscribe to the Taylor industries theory? I would like to know your position on this not so well adapted calculation.