Pool Chemistry TA

[chem geek]

Most excellent advice. One can use The Pool Calculator to automatically calculate the saturation index taking into account the CYA level (among other things).

Yes, the TA should be adjusted (within reason) so that the pH is stable. Generally speaking, to get more stable pH it should be lower if you are using hypochlorite sources of chlorine (chlorinating liquid, bleach, Cal-Hypo, lithium hypochlorite) and higher if you are using Trichlor which is very acidic. Even Dichlor is net acidic when accounting for chlorine consumption/usage (which itself is acidic).

The unique "personality" of every pool is really the variability in the possible sources of pH rise, most notably in the variability of the aeration of the water. Pools with pool covers using hypochlorite sources of chlorine tend to be much more stable in pH and much less dependent on the TA level. Pools using hypochlorite sources of chlorine with lots of aeration from waterfalls, spillovers, fountains, etc. tend to rise in pH much more unless the TA is lowered substantially. Pools using an SWG tend to rise in pH and lowering the TA helps, but doesn't usually completely resolve this problem -- having a higher CYA level and using 50 ppm Borates can often let one turn down the SWG on-time and that lowers the rate of pH rise.

In pools with curing plaster, the pH will rise a lot and since this is not due to carbon dioxide outgassing there's not much to be done except add acid frequently and wait...the curing rate decreases over time.