How to do you guys go about measuring Muriatic Acid for your spas? Being that my spa is 330 gallons, in doing the math it looks like I'll be looking at about 2 tps to drop from 8 to 7.2 pH. I haven't filled up the tub yet — more or less just getting prepared with what I'll need. Acid comes in 1 gallon jugs and we're working with such small amounts that it's a little tricky. Do you have some kind of special device you like to use? I did some searching, but the only thing I came up with lead to a dead link for a product. Also, do you folks use some kind of respirator mask when working with this?