A non chlorine oxidizer or ‘shock’. It is acidic and will cause lower pH and TA. It adds sulfates to the water. Will not break down CC but helps prevent it from forming when used on a regular basis. It will interfere with TC and CC tests unless special reagents are used in testing since it WILL test as CC! A good choice to use in indoor pools that are not exposed to sunlight but really has no advantage in an outdoor pool. It is only an oxidizer and NOT a sanitizer and should not be used as such.