H376 composting toilet install

Nov 24, 2018
27
Hunter 376 Medora, ND
One of our first projects as new owners was to replace the tired marine head (and accompanying systems) with a composting unit. We chose the C Head line of products after a lot of research and comparisons. And then after some measuring and estimating we figured their Wedged Back model would fit the best.

When it arrived we took it out and measured some more--still seemed like it would fit. So we began removal of the old head. It hadn't been used for a while and we got pretty lucky with no nastiness coming out of any of the disconnected tubing. We also removed the hose to the black tank, the black tank itself, and the macerator.

The hose pulled through the hanging locker pretty easily. We threw out the chair, etc. next to that since it was heavily water damaged. We removed the low cabinet and the foot of the bed since the hose ran through that. A lot of the wood for this part had absorbed sewage smells and stains so the Admiral did not approve of putting this wood back in the boat, so regretfully we do not have this low cabinet anymore. And finally we removed the shelf and the plywood sheet covering the forward side of the black tank. It didn't all go in that order but it was a couple months ago.

A septic service company came with a shop vac and sucked about 10 gallons out of the black tank, with an estimated 3-4 gallons remaining. The input port on the top basically crumbled away when I detached the input hose from it, so the tank was at end of life. I'm glad we never filled it! That crumbled hole is where they put the vacuum hose in. We double bagged the tank and hauled it out of there, thankfully again with minimal nastiness leaking out. Very heavy though! The metal frame of the bedroom door had to be removed in order to get the tank to pass through, and would probably be necessary for the fuel tank too. And then I removed the macerator and that associated plumbing.

The fiberglass base that the old head sat on proved to be suitable for the new composting unit to sit on. The only issue is that it ends up being about 4-6 inches too high for a normal person to sit on so we use a stool for our feet. Many people use "squatty potty" stools anyways, right?! The base of the enclosure is not fully supported but seems to be strong enough for that to not be an issue. The enclosure is screwed into both the fiberglass base and through the "wedge" part into the cabin liner. It is rock solid!

We ventilated our unit through the back of the enclosure (did not opt to ventilate straight out of the compost bucket) using the hose that it came with, plus some additional to make it long enough. The vent hose leaves the bathroom the same way that the old sewage line did, through the hanging locker in the bedroom. Then we ran it up to the ceiling and followed the ceiling/wall edge back to where the pump-out hose passed through the bottom of the lazarette. The vent hose goes through there into to the lazarette and makes a loop before exhausting out of the old pump-out hull fitting. At the top of the loop I installed two 12V fans and wired them up to the old macerator wires. Then I relabeled that breaker "Head Vent". We let the fans run continuously. At the bottom of the loop I poked a tiny hole so that any rain that gets in via the pump-out fitting will seep out into the lazarette before getting to the fans. Admittedly this sizable opening might be a risk for any serious offshore sailing but that is not in our current plans and there are other larger deficiencies when it comes to that. I plan to fiberglass over the old access hatch for the black tank in the floor of the lazarette so that this seepage does not drip into the storage area that we now have where the black tank was. Instead it will seep through a hole closer to the rudder and go into the bilge. But so far there has not been enough to even fill a groove on that side of the lazarette so that it would need to flow anywhere before it evaporates.

We are pretty happy with the composting toilet overall. Odors inside of the bathroom are fine. Emptying the urine jugs in a responsible way is surprisingly worse than disposing of the compost. At the back end of the boat we occasionally catch a musty whiff. We are still learning what works best for quantity and type of composting medium so when we really mess that up then the whiffs are worse than musty! Currently we are using coconut coir. It's fine but I may vote to try peat moss next for a variety of reasons.

Just wanted to write this up in case it helps anyone!
 

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Tom J

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Sep 30, 2008
2,301
Catalina 310 Quincy, MA
Thanks for the post. Composting toilet is on my bucket list, no pun intended! Nice to get rid of that holding tank and associated plumbing.