Quote Originally Posted by cleancloths
That is really strange, because if you tested the pH of bleach you would find it off the chart (to the high side). I find that my pool stays at a perfect pH level if I use a mix of 3" pucks which drop the pH and Bleach which raises it.
Sorry to have jumped into this one so late but even if the PH of chlorine is at 11, it will not affect the pool that much. The resultant PH of 1 gallon at PH 11 and 20,000 at 7.5, assuming no buffers (i.e. worst case):

ph = -log10 [(1 * (10^-11) + 20000 * (10^-7.5)) / 20001] = 7.500022

Virtually no change at all. Acid is a different story. Because it is close to 0 and the formula is logarithmic, it has a much bigger impact on PH.
ph = -log10 [(1 * (10^-1) + 20000 * (10^-7.5)) / 20001] = 5.3

A big difference. Unfortunately, these formulas are for solutions without buffers but they do give you an upper limit on PH swings.