Off Beat came with a nice clean Groco standard marine head. It had been recently rebuilt or replaced. But I wanted something less efflusive and maybe better -- a composting toilet.

Choices

There are 2 popular composting heads for boat use: Air Head and Natures Head. Practical Sailor did a review (20 years ago now!) comparing Air Head and EcoLet. For me, EcoLet was too big and used too much power, and AirHead seemed a bit more small-boat-friendly: shape of the base tucks back into the hull a bit better and it's made in Maine. So AirHead it is!

Planning

It should be installed against the starboard hull, on the raised platform like the old one was. However, the new toilet is a full 20" tall, so:

1. It blocks the door to the wet locker behind.
   This is the only hanging space in the whole boat! Probably fix by replacing the door with a sliding door or partition. I'll still have to reach around the toilet, but should have the full use of the locker.

2. It's too tall for me to sit comfortably because of the few extra inches of hight from the raised platform. I may try to cut into the platform and set the toilet directly on the hull (need to shim it level); or mount the toilet on a big ply platform; or install a moulded step on the pan of the head compartment to reach the base of the toilet.

Removing the old head and tank

This is the fun part. We get to remove 8-10 feet of stinky old hose, the diverter valve, a 15 gallon holding tank from under the quarterberth, and get to close up a hole in the hull.

Running the exhaust

This toilet has an exhaust vent with a constantly-running fan. I was thinking to vent it out a hole in the cabin (with a solar muffin fan and battery backup), but MaxMar suggests running it through the wet locker and out the side of the hull, where the smell won't flow back to the cockpit. There's an existing vent loop vent there. I like the idea, but worry about bashing the vent during docking and also about water intrusion into the hose (and fan, which should be at that end). One idea is to make a tall vent loop and instll the fan right at the bend, so it's protected from boarding water.

Power

The exhaust fan should run all the time. Maybe solar powered with house battery backup?

Results

Contracted the work out to MaxMar, LLC, without whose expertise I would not even attempt this.

Update 1-Feb-2022: And now, it's done! It's a nice, clean install.

Fits well enough side-to-side.

Comfortable to sit on with your feet up on the liner, so no extra stand seems necessary for now.

The exhaust hose goes up the forward bulkhead in the wet locker, so it will be mostly out of the way. It needs connection to a permanent power source, good thing the house bank is big.

Top of loop is just about 8" above exit, this should be enough when the boat is heeled.

Follow up projects

No boat project is complete till you've made a list of the follow-up work desirable or necessary.

Necessary:

• thin composite board on top and in front of the liner, just to cover the holes.
• Something to cover the hatch into the wet locker. Maybe a tambour door?
• Clamshell cover for vent hose exit, to keep splashing waves out.
• Laminated "care and feeding of the head" sheet to hang on the door.

Nice to have:

• Some kind of fixed passthrough fitting where the vent hose goes through the wall of the wet locker, to make it easy to disconnect the hose when emptying the solids bowl (every few months).