composting toilet report
In a discussion of heads late in the spring I mentioned that I had installed them in my boat and a few people asked me to write up my experience with them, so here goes.
First a bit of background. I bought my J40, Genie, in the fall of 07 and began a lengthy refit. I had read on this site about composting toilets and was intrigued by the concept. I also really hated the amount of scarce boat space that was given over to holding tanks, pumps, valves and hoses . On the other hand I was still more than a bit uncertain about the whole concept of composting aboard a small boat.
My initial compromise in the spring of 08 was to take out the aft head and replace it with a composting fixture. Why a 40’ boat has two heads is another thread and one that I won’t go into here. Suffice it to say that that’s what I had and what I had to deal with. It did afford me the opportunity to change one head and keep the other as a safety.
In the summer of 08 I took Genie on a cruise to Nova Scotia from my home port on the Hudson River. Everyone on the five man crew was quite leery of the composter and preferred to use the forward, old fashioned, head. While we were far offshore on the crossing from Provincetown to NS I decided to try to pump out the fwd holding tank. Something didn’t feel right as I did so and I took a look under the bunks in the forepeak.
When I lifted the bunk boards I nearly had a coronary. The poly tank was bulging out in all directions and looked to be one more pump stroke from bursting. I had visions of driving the boat ashore and walking away from it never to return if something did burst. I had to open the deck outlet to relieve the pressure, resulting in a 2 foot gyser of raw sewage. Much scrubbing and cleaning later I swore to rid myself of all parts of that system, which had smelled bad anyway. (When I was dismantling the system later I found a sanitary product in one of the hoses that blocked the overboard discharge, the gift from a bubbleheaded guest of the PO)
During the return trip we were able to use pump outs and the crew remained shy of the composter in the aft head so I didn’t really have a chance to evaluate it, though I used it religioulsy and found no problem with it. Last winter I removed the all the vestiges of the plumbing system and put in a composter in the fwd head as well.
This summer we cruised to Maine. I had anywhere from 2 to 4 crew aboard for a period extending to three weeks of sailing. People had to use the composters (or hang their posteriors over the pushpit) since we spent relatively little time at marinas. It was anchor or mooring, so they overcame their reluctance and used them. By the end of the cruise everyone was somewhat embarassed over their original reluctance and had gotten completely over their hang ups about it.
To fully discuss the pros and cons I have to give a brief description of the units and how they work. Essentially, composting toilets are made up of one “bucket” over another with a trap door between the two compartments. When the trap door is closed and liquid is deposited it runs into a removable 1 ½ gallon bottle in the front of the unit. There is a SS crank that can be used to agitate the contents of the lower container that is filled about halfway with peat moss and enzymes. A 1 1/2 “ flexible hose with a fan at the deck end keeps a negative pressure in the lower tank to prevent odors from escaping.
If you are making a solid deposit you take a coffe filter (like those from a standard countertop coffe maker) and place it over the trap door. When finished you flip the handle that opens the trap door and your contribution drops to the lower compartment. The bowl is left clean because of the coffe filter. You take a couple of turns on the crank to mix your donation with the peat moss and that’s it. If your donation was of the liquid variety I found it helpful to take a half a cupful of water to rinse the bowl and prevent it from developing odors.
Wow, I didn’t mean to write the introduction to a book. At any rate here is what my conclusions are after one season of use:
Odors were not a problem with two exceptions. The urine bottle has to be emptied every couple of days or it does begin to get ripe. I have heard that a half a cup of sugar in the bottle keeps the odors down but I haven’t tried it and I’m not enough of a chemist to understand if and why this would work. On the other hand it is not that difficult to clean out, either by taking the bottle to a shoreside head or by dumping it overboard (unless you are in a very closed harbor or a lake).
Part of the way into the trip one of the heads did begin to smell a bit, even after the bottle had been cleaned. A quick investigation revealed that the fan of the solar vent I had set up on deck to create the negative pressure to vent the unit had been jammed by a bit of caulking and was not functioning at all. I was pretty impressed that the unit had not smelled bad after a week of regular use even with no ventilation. I scraped off the caulk and had no problems from that point on.
We also discovered that the amount of toilet paper used by the number of people aboard tended to jam the lower compartment a bit. I was using regular TP so I don’t know if using a rapidly degrading variety would work better, I’ll experiment with that next year. I remembered that years ago, while in Greece, we were warned that the sanitary systems there did not swallow TP very well and near each toiled was a plastic bag into which you were expected to place the used paper. I bought some plastic zipper seal sandwich bags and instructed the crew to put the TP in the bags and thence into the garbage. Everyone caught on and dealt with it with no problem. The head was too small to install a bidet as an alternative.
The units themselves are pretty tall and it felt a bit funny at first to be so high, a bit like a kidergardner using grown up chairs. Most heads are placed on a shelf built into the liner so it is impossible to lower them. I am considering putting footholds so legs don’t dangle in the air when sitting for shorter people. I got used to the altitude pretty fast as did the regular crew. It took some of explaining to guests.
And that’s it for the downside. Not a long or impressive list. How about the upside?
Well, first of all, I am confident that I can deal with any head problems. These are extremely simple mechanisims. Nothing is hidden from view or inaccessible or impossible to reach. Everything is comprehensible and fixable. That is a huge plus. I also make sure I always carry a good supply of rubber gloves.
You don’t need any assistance from the outside – last year in Nova Scotia where holding tanks were not required we had to search long and hard for a pumpout station. If your unit is overfull and you are offshore you just take the lower “bucket” and dump it overboard, rinse, refill with peat moss and start all over again. Total material from a crew still equals less than one poop from a medium sized whale, just make sure you are well offshore.
By removing all the tanks, pumps, valves and hoses I gained a tremendous amount of room. Both compartments under the two sinks were opened up for additional uses. The removal of the two holding tanks allowed me to install an additional 20 gal. diesel tank and to relocate my batteries.
The boat smells a hell of lot better. The hoses were getting ripe after 18 years of use and I didn’t relish the job and/or the expense of replacing them. If you keep the composters clean they don’t smell.
On the whole I’m glad I did the switch. There are problems but to me the problems are manageable because the system is simpler and much easier to maintain. If you sail for long periods with more than a couple of people one head may not be enough. My experience is that I can handle larger volumes for short periods or smaller volumes for longer. The manufacturer claims 80 uses during a season, you do the math. You leave the compost to work over the winter and in the spring the compost can be dug into the soil of your flower garden (not the vegetable garden!). I didn’t want to discuss this with the Real Boss and so I fertilized some woods we own across the road. The deer didn’t seem to mind and the material was indistinguishable from “black dirt”. This year I might put it in the flower garden after all. This might be more difficult if you live in an apartment.
So this is what my experience has been after one season. I am not an expert by any stretch of the imagination but if asked if I would do it again on my next boat (if there is a next boat), I would say yes.
Last edited by genieskip; 10-03-2009 at 09:43 PM.