There are three basic types of marine head: self contained porta-pottys, fixed plumbing systems with holding tanks and complex systems that can treat raw sewage so it’s safe to pump directly overboard. Most common are fixed plumbing systems.
So. How do they work.
A manual marine head consists of a porcelain bowl, a hand-pumped raw-water intake, and a discharge elbow. Once the user has made a deposit, he or she actuates the pump by hand TWENTY TIMES. Put the leaver on the ride side and pump the water into the toilet. After depositing, put the leaver back on the right side and drain the head. Make sure you count the strokes as the water has to go a long way towards the exit. Leave the leaver on the right side so that you close the in-lead valve of the water.
Never flush anything that didn’t come out of you.
This one’s pretty easy. Hopefully you already know that the only thing that should go down your marine head is human waste and toilet paper — with no exceptions. But the likelihood is that your guests have no idea. Unless you want to be picking dental floss, feminine hygiene products, or old parking tickets from a clogged-up head, make it clear to your guests that if they didn’t eat it first, it doesn’t go down the head. Now, there’s no delicate way to put this, but if you or a guest end up having to make a large deposit with a lot of toilet paper, flush when half-way through and then again when finished to avoid a clog. Moving a little through at a time is much less likely to cause a clog than trying to flush everything down at once.