What chemicals are used to start up a pool while filling?
First off, test the water going into the pool to determine its “native” pH, chlorine level (municipal water usually has trace amounts), its alkalinity (its resistance to swings in the pH), & its calcium hardness. pH/alkalinity is first. Get the pH balanced, then add chlorine, also get some floater dispensers. I recommend getting a test kit for use once or twice a month, and a cheap little kit for daily use. I use alkalinity increaser for alkalinity issues, muriatic for pH acid down and pH increaser for pH up. Learning your waters native alk & pH is 3/4 the battle. Then just keep it chlorinated to kill the beasties.
