Searching for more about "Operating Swiming Pools at High PH"...

[chem geek]

Anyway, I put in about 1/2 of what the booklet recommended for a 5000gallon pool at 2 drops acid demand.

From the Taylor booklet I have the half-amount (or 1 drop from the acid demand) in 5000 gallons is 4.6 fluid ounces of full-strength Muriatic Acid (31.45% Hydrochloric Acid). Diluting this amount in 5 gallons of water would have the pH go from -1 (yes, that's negative 1) of undiluted acid to +0.4 so still very acidic. Even pouring slowly into the skimmer doesn't help that much with the pH. Even if you poured at a slow 1 gallon per minute (about 1 cup every 4 seconds) with a skimmer flow rate of 20 GPM (so 1:20 dilution) the pH would still be +1.7 which is still low. pH is a logarithmic scale where every factor of 10 dilution of a strong acid or base solution is a 1 unit change in its pH.

As waterbear noted, you really want to add the acid to the bulk pool water and mix it. As he noted, the safest way is to pour slowly in front of a return flow with the pump running and then to lightly brush the side and bottom of the pool in the area you added it to ensure thorough mixing. In fact, most pool products (acid, chlorine, etc.) are denser than water so if you add them too quickly in one place they can pool at the bottom. For some chemicals such as salt or borates, this might not be a big deal but for acid and chlorine it can. Once mixed, however, such chemicals remain mixed.

By the way, it is this post on this forum where I first put up the chlorine/pH relationship with and without CYA.