Since I was out there, I decided to grab some photos of the marine toilet on Seas The Day. (Some of our readers have asked about it.)
Unlike in your house - where you can just flush the toilet and everything is taken care of - a marine "Head" (boat speak for "toilet") is a bit more complex. The complexity starts right at the toilet. If you look at the photo below, you see some things that are recognizable - the bowl - but also a lot of hoses and levers. You'll also see a pumping handle (near the blue oval) and a lever just above that. The lever switches between a wet flush and a dry flush. On a wet flush, you pump the handle and water enters the bowl, as the waste is pumped out. On a dry flush, it just pumps out the waste. Why would you ever want a dry flush?
Well, the water for the wet flush comes from the sea. The thinking is that you really don't need pristine water to flush a toilet and since we only carry 27 gal of freshwater on board, flushing with seawater is fine. And it is... except on a system that gets relatively little use (like ours... mostly day trips of 4 hours or so), the little marine critters can start growing and you can get some foul odors. So we usually select a dry flush and do the rinsing with water from the sink (the "faucet" is actually a short hose - it also doubles as a shower).
So the pump takes the waste from the bowl and moves it through the little pipes. Yes, little pipes. They can clog easily and the first rule of using a marine head is that NOTHING goes in the bowl that hasn't been eaten first. The sole exception is a little bit of toilet paper. We have been good... so far I have not had to unclog it (you have to take it apart... sh!t and all)... I hope that trend continues.
So the pipes go behind the toilet and into the salon where most of the waste holding and processing takes place under the U-shaped settee.
The main waste pipe basically comes into the holding tank. (The little compartment that it passes through holds the freshwater pump.)
The holding tank has a vent that goes up the side of the boat and exits. I've learned that noises coming from that vent are cause for concern.
At the lower right, you can just barely see the exit hose from the holding tank. It connects to the larger hose from the lower right below. That hose goes to a grey T and continues up to the waste port on deck (photo below). Attached to the T is our macerator pump, which is kind of a sh!t blender that can pulverize the solid waste as it pumps it overboard through the "Through-Hull". USCG states we have to be 3 miles offshore to do that so usually the through-hull is secured with a wire tie in the "closed" position. (We typically don't get 3 miles offshore unless we're going out specifically to ensure the macerator is still working.)
The photo below shows the (new) waste deck plate on the port side.
Once you put the covers on it all, it's hard to believe that a sewage holding facility is just below the seats.
I wrote all this because a few people who are considering the purchase of this type of boat had some questions. Here are some additional thoughts about this sh!tty subject.
First, the system seems to work well and be designed right for the type of sailing this boat is intended for. A Catalina 315 like Seas The Day just isn't designed for long ocean-going voyages. If I had it to do over again, I wouldn't bother with the macerator. We used it on our delivery trip when we spent 2 days sailing on the ocean to get it home, but since then we've only been 3 miles offshore once each season to test it.
So we mostly use the holding tank. That means we have to have the tank pumped out which for us seems to be a once a month need. We are lucky to have a nice pump out boat moored right in Keyport and a small tip ensures this task is completed when needed. Our sailing also takes us to a land based pump out facility from time to time. (We did learn the hard way that we can't let too much time pass before pumping out.)
Finally, although I'm talking a lot of sh!t... the real bad actor here is urine. Urine has a high concentration of urea and salts, etc. which depending on conditions can crystallize in the hoses. We have been following the advice of putting a cup full of white vinegar in the head, pumping a stroke or two and going for a sail. After that we pour a 1/4 cup of vegetable oil and slowly pump that. So far that seems to have kept the lines free and the various seals well lubricated. By flushing with freshwater and doing that little bit of routine maintenance, Seas The Day has finished two seasons with only the one mishap.