If you have no chance of having any dichlor or trichlor in your skimmer, pump, filter, heater, or feeder or anywhere but in the pool, you can slowly dose cal-hypo into the skimmer - it will dissolve on the sand bed and leave it's calcium precipitate there. But Remember - NO trichlor or dichlor anywhere near the circulation system - Cal-hypo and stabilized chlorine have a surprisingly energetic affinity for each other. We don't want your filter to go BOOM after all.