Dear Boat Doctor,
The head on our 2000 Jeanneau 40 has a slight odor. It's nothing awful, but you can tell what room you are in with your eyes closed. We have scrubbed everywhere we can reach. Every hose and fitting feels completely dry, likewise around the stainless holding tank. Water is in the toilet bowl and shower drain creating an air seal. Our sniff searches have not lead to a particular area, yet the smell seems to come creeping back when the room is closed. How do we make it go away?

There is a shelf full of products made to go into a toilet or a holding tank. What do these do and are they necessary? I know some work by creating their own overpowering scent. We have not used these products in the past but we've never had an odor problem before.

Lynn Deedler
via e-mail

Dear Lynn,
A smelly head can be tough to live with, but there are a few things you can try to remedy the situation. Assuming your head equipment is functioning correctly, there are two smell sources you could be experiencing, the head discharge hose or foul flush water. Head discharge hoses tend to become saturated with sewage and begin to smell.

The best way to test if this is the case is to wipe down the hoses with a warm wet rag and then smell the rag. If the rag smells "heady" the hose is leaking odor. Your only choice is to replace the hose. Buy the best hose you can and be prepared to open your wallet because hose is expensive. Even the best hose will eventually become odor permeated, but you should get five or more years out of a top-quality hose.
If your boat is in salt water, your flush water can begin to smell in the bowl, but this is more of a sulfury smell. The saltwater flush water that you draw into the boat can have organisms in it that can die and emit an odor. To combat this you can flush often to rinse out the stagnant water, do a final rinse and flush with the shower, or even replumb your head to use tank water.

There are many head chemicals on the market that contain chemicals to control odors, breakdown waste and tissue, and contain detergents to keep the hoses and tank clean. Additionally a few companies make enzyme-based products that provide the same benefits in a more green way. I have had great luck over the years with the chemical-based solutions from Thetford (www.thetford.com, 800-543-1219).