Peggy, I installed a new holing tank, from Ronco, and new waste and vent hoses this spring. I am using Kills Odor and only fresh water when flushing my head. Occasionaly a very strong odor will eminate from the vent thru-hull when you flush, and if you get close to the fitting there is an odor at all times. Am I not using enough KO or not enough water when I add the KO after pump out? I am not using any other chemical as suggested on the KO bottle, and we rinse with Vinegar and Fresh Water when we leave after the weekend. I appreciate the help. Andrew Boyer