Muriatic acid vs pool pH decreaser: Muriatic acid is cheaper and stronger, but requires caution

Muriatic acid (hydrochloric acid) is cheaper, more concentrated, and works faster than commercial pH decreaser (sodium bisulfate). You use way less of it, but it’s nasty stuff — wear gloves and goggles, add slowly to a bucket of pool water, and start with half the dose. For a chemical-free option, CO2 injection works by forming carbonic acid.