Re: calgon It sure seems like you're picking on Kirk in every post. I'm glad he had the good sense to call Calgon and ask about it. That doesn't mean what you do is invalid. I do my black tank with just water most of the time. Then on the last leg, I'll put in some detergent and calgon so it gets swished around. Then I dump it in my home septic system and rinse it real good with plain water. So I mostly do what Kirk does, but not 100%.