mix for black tank using calgon water softner

I have automatic dump valves and every trip the black tank valve would stick and not open. Had to crawl under the trailer with a hex key and free it, not pretty on wet ground. Prior to our first trip of the year I threw some Calgon and detergent down the hole with 5 gallons of water. Auto valve worked perfectly. I don't know if there is a correlation but the same stuff is going down next time. I just guessed on the amounts.