Flocculants, muriatic acid, sodium bisulfate and calcium chloride are chemicals used to adjust the hardness of pool water. Flocculants are used to help clump together minerals that have gone out of the solution. These clumps of minerals are easier to filter or vacuum out of the pool water.
Removing minerals from pool water lowers the hardness of the water. Muriatic acid and sodium bisulfate are used to balance the hardness levels of the pool water. Calcium chloride is the primary chemical used to raise the hardness of pool water. Water that is low in minerals corrodes and leaches into pool parts made of metal. Adding calcium via calcium chloride directly increases the mineral content of the pool water and consequentially, increases the harness of the water.