Pump your lines on close up
When you close your boat up for the week and close your valves for the heads, be sure to go back to the head and pump the bowl and hose dry as best you can. If you leave water in the bowl, that means there is salt water still in the hose. That water is full of living creatures. The next weekend when you come to the boat, the first use of the head will about knock you out with the rotten egg smell. So, close the through hull first then pump dry. When we do that, we dont have the smell at all.Now, if the smell is coming from your holding tank vent on the outside of the hull, that is a completely different problem and you must go to the Head Mistress Forum and read her article on eliminating head ordors.