Swimming Pool Acid

[chem geek]

You can use it. The only downside is that you will add to the sulfates in your water. You also end up adding sulfates when you use non-chlorine shock (potassium monopersulfate or KPMS). This is not a problem unless the sulfates get really high at which point it starts to affect water chemistry a little bit (makes the water more corrosive and less likely to scale), but it would take a heck of a lot of sulfates to cause that so I wouldn't worry about it (300 ppm of sulfates would be equivalent to lowering the pH by 0.1). Just get Muriatic Acid whenever you run out of this stuff.

As for how much to use, it is very close to the Muriatic Acid in effective acid concentration per volume, though you can verify this by looking at the bottle to see how much it says to use to lower pH. Though sulfuric acid has two hydrogen (H2SO4) compared to hydrochloric acid (HCl), it is more than double the molecular weight so this along with the 38.5% vs. 31.45% cancels out (I suspect they chose 38.5% concentration so that the acid was close to the 31.45% Muriatic Acid concentration).

One cup of sulfuric acid in 10,000 gallons adds 5.9 ppm of sulfates so it would take a whole lot of acid before you started to see any impact from the sulfates. One cup of non-chlorine shock (KMPS) adds 5.1 ppm of sulfates so is about the same in that effect.

Richard