I don't know where you live, but if you have a Tractor Supply Company chain of stores where you live, they sell it at 31% strength in 1 quart sizes, as well as the gallon sizes. Don't worry about the calcium hardness, in a vinyl pool it won't matter. The alk will come down when you adjust the pH down. Now you need bleach for chlorine, and CYA to protect it from the sun.