I have a 1200L hot tub and use chlorine granuals as my sanitizer and non chlorine shock as well. Lets say I go to use the hot tub... The free chlorine level reads 2.5ppm. After use the free chlorine would be converted to combined chlorine and would read 0ppm free chlorine. So now do I... A) add the non chlorine shock first, then add chlorine granuals. or do I add chlorine granuals first then the non chlorine shock.