I get a horrible rotten eggs/sulphur smell whenever i use the head after not having used it for a couple of days. I recently saw a device in the Boat US catalog (i cant recall the name). I hooks up between the head and the sea water intake. you put a "disc" in the device and it chemically treats the water which stays in the intake line when the head is not in use. every time you draw water into the head, it passes over the disc and gets deodorized. The disc is basically a chemical "block" about with a diameter of about 3 inches and three inches thick. It is supposed to last about 1 month.any experience with this product?