AbbeysDad has the answer. I would add one thing though...after the rinse you must air dry the entire length of tubing before using it (assuming it is used to fill a tank with fish; if using only to drain, this doesn't matter). Bleach can remain unless air dried. I went into this with a microbiologist friend a few years back. I have never bothered to do this because I have 75 feet of tubing to connect the sink to the fish room tanks and I could not see how I was going to lay this out in order to dry it. Water (or moisture) remains in it from week to week now.