Peggy: Some feedback - About two weeks I described a problem with an almost new H-306 (Jabsco head) which has just recently started bubbling back gasses into the toilet bowl. The tank vent had been flushed thru and seen to be open. Hunter's dealer checked it today and found a deformed flapper valve just ahead of the joker valve. He replaced both valves and the head is now OK. Their knowledgeable tech rep said that we "had done all we could to keep the head system odorfree and operating". All we did was what you said to do!!!! This note is just to let you know that your super technical skills and boundless patience are greatly appreciated. Thanks again. As for those who won't check the archives, or read your book, as we used to say in the Navy: Illigitimus non carborundum! (Don't let the Bast..ds wear you down)