I just added 54lbs of calcium chloride as needed post Hurricane Harvey in the Houston area. I was desperate and bought it from that pool store that will not be named (rhymes with stresslies) and it cost me an arm-and-a-leg. I know don't say it, but I was desperate. Where do y'all buy Cal Chlor to feel less fleeced? Also, how long can a plaster pool go with really low Calcium levels before it starts compromising the plaster? A week? A month?