UPDATED JULY 2018
Low spots in the hoses retain waste and smell bad, so tip number one is to make sure there are no dips or kinks in your plumbing. Try these other tips for keeping your boat’s head odor-free.
1. Pump out frequently.
2. Following pumpout, filling the holding tank with a 50/50 mix of bleach and water works great. Fill the tank with this, then pump-out at a shore station–not into the water, as bleach kills just about everything. ( NOTE: To avoid conflict with manufacturer recommendations, add the bleach/ water solution to the tank through the waste pumpout fitting on deck, not through the commode.)
3. After the tank is empty, add two cups of water softener, available in the laundry department at the grocery store, dissolved in hot water. The softener prevents solids from sticking as much to the tank and lines.
4. Install a water filter on the intake line–if you fill with a hose, there are hose filters. This is will keep out some of the critters and minerals that can start the smell.
5. Change the hoses regularly. Frequency of change depends upon use, but at four years max, swap out for new hoses. Most of a boat head’s odor comes from here.
6. A boat head that flushes with freshwater from an onboard tank is less prone to odor than one that uses raw water from the lake, bay or ocean.