Composting Toilet

Installing a Composting Toilet

In 2008 the toilet in Sarah's head was showing a lot of age and needed either to be replaced or a major overhaul. Also the LectraSan sewage treatment system was about to give up the ghost and it was not even legal in many areas of the US. So a holding tank was probably going to be required, something that would be difficult to fit on Sarah and a lot more plumbing. After having to clear a sewage hose on the way from Bermuda back to the Chesapeake Bay in 2007 I started looking for alternative to the standard seawater flushed marine toilet.

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The only real alternative is a composting head - one that does not discharge sewage, but rather allows it to compost onboard turning it into fertilizer. I heard of this type of head for years, but the concept seemed a bit extreme. However as the concept of a discharging head became more and more undesirable, the alternative began to appear much more acceptable. Practical Sailor had done a review of several composting heads back in 2002, and they concluded that it was a workable solution for a marine toilet. I also heard from several live-aboards who installed composting heads on their boats and were very satisfied with the arrangement.

At the time I was only aware for one brand, the Airhead (shown in these pictures), from the Practical Sailor article, the live-aboards, and boat shows. So in 2008 I purchased the Airhead and began planning the installation. Subsequently I learned of another brand, Nature's Head, which also would be a good solution for Sarah's Head.

The base of the toilet is the composting chamber. The toilet bowl detaches from the base and the base can be removed from head to dispose of the compost periodically. Live-aboard couples claim they can go up to six weeks without having empty the chamber. The other chamber protruding from the base is the urine bottle. The secret to composting is to control the moisture in the composting chamber. If urine were added to the chamber the compost process would take much longer (until the urine evaporates) and probably would produce unpleasant odors in the head.

This is the business end of the Airhead. In the interest of good taste I've taken these pictures before the Airhead was installed and before it was ever used in anger.

In this picture the trap door to the compost chamber is open. That is all there is to flushing this toilet - allowing the waste to drop into the chamber. The manufacturer recommends using Mr. Coffee-style coffee filters to catch the waste before the trap door is opened, but several users claim they no longer use the filters, but just drop their business directly into the chamber.
Maybe this is more information than you really want.
The two holes in the toilet bowl, forward of the trap door are used to collect urine. Yes, this is a gender-equalizing toilet. No one gets to pee standing up in Sarah's head after this toilet is installed.

The Airhead uses a standard compact marine toilet seat - the same as on the Raritan PH-II head that came with Sarah. One difference is that the Airhead provides gasket seals on the bottom of the seat and the lid to contain any odor.
One of the advantages of the Narture's Head composting toilet is that it has a standard household toilet seat molded into the unit. Since my butt is definitely not a compact size the full-sized seat might be a significant advantage.
Still I've managed to get my business done on a compact seat for the nearly 5 years of living onboard, so I guess I can continue to get my business done on the Airhead.

The major installation task (other than removing all the old plumbing) is the installation of the vent which brings air into the composting chamber. I wanted the vent hose to be out of the way on Sarah and not take up a lot of valuable space in the small head. The ideal spot is in the little alcove just outboard of the companionway stairs that are on the opposite side of the forward bulkhead.
So first I removed the headliner. This involved removing a lot of molding and trim pieces. Even then the headliner resisted coming out. Clearly the headliner had never been removed from the head since Sarah was built.

The headliner did finally come free and I could see the underside of the trunk cabin where I intended to place the vent. There is a 1/2"x4" piece of wood glassed into the corner of the trunk cabin to provide stiffening. The 3-1/2" hole for the vent would have to partially cut into this stiffener. That meant I would need to fit some cleat stock inboard of this to provide a flat surface to attach the vent fan.

The first task was to cut the hole in the trunk cabin with a 3-1/2" hole saw. The edge of the cut-out is shown in the picture on the left. The trunk cabin is about 1-1/2" thick with a 3/8" outer skin of fiberglass and a 1/4" inner skin with 1" of balsa completing the sandwhich.

On the right is the hole in the deck with the cleat stock installed.

On the left and below is the deck vent fitted next to the companionway hatch.

This is a passive 3" Nicro vent.

In this picture the headliner has been re-installed and the vent fan housing installed under the new opening in the coach roof.
I cut this corner of the headliner off from the main piece. This made it easier to cut the hole in the headliner for the vent opening, but it will also allow me to remove the main part of the headliner in the future without disturbing this vent for the toilet.
The fan housing is secured by screws that go through the headliner, through the cleat stock, into the coach roof. This housing must support the weight of about 6' of 1-1/2" vent hose, so I want it to be very secure.
Now all I have to do is hook the fan up to a 12 VDC supply and I can remove the old PHII toilet and install the Airhead.

This is a picture of the vent opening in the coach roof with the Nicro vent removed. The vent fan is visible.
Yes, I know I really chewed up the coach roof gel coat with the hole saw. I drill one of these holes about every 5 years and I always forget that when using a large hole saw in hard material you have to run it in reverse, at least until you get through the outer fiberglass shell. I am starting to believe I have forgotten more things than I ever knew. Getting old is a bitch.

While I was messing with the headliner and trim pieces I decided to finish covering the places where the wall paper had been removed during the bulkhead replacement. I found some of the Butternut stock I had used for trim around the bulkhead. I used that wood to cover the gaps in the wallpaper. I still have to shape the pieces a bit and then varnish them to match the other Butternut trim in the head. They will not match the original teak trim pieces, but I will not add anymore teak to Sarah' interior or exterior.

Finally on May 30 I removed the Raritan PHII toilet from the head. I also remove the pedestal on which the toilet was installed. You can see the outline of the pedestal around the large hole in the floor of the head through which the seawater intake and seawater outtake hoses were run.

This hole is in a a platform above the cabin sole on which the toilet pedestal was secured to mahogany cleat stock. Removing the cleat stock turned out to be the most difficult part of the de-install. Removing the counter-sunk wood screws required a lot of pressure a Philips-head screw driver with the added leverage of a vice-locks wrench. The final two screws had to be drilled out.

In the picture on the right I have placed the Airhead in what I expect will be its final location. I decided to wait over night before securing it to this position and then cutting the vent hose to length.

The next day I secured the brackets that hold the toilet in place to the toilet platform. I then cut the vent hose to length and attached it to the toilet bowl.
Now the installation is basically complete. The big (and unpleasant) job that remains is to remove all of the water and sewage hoses from Sarah along with the LectraSan. This will be a messy and complicated job. To remove the LectraSan I will need to remove all of the water pumps (frig, A/C, shower) that currently reside just aft of the LectraSan. While I'm at it I will remove the low-volume seawater manifold and clean it up.

I am a little concerned that these SS brackets will be strong enough to withstand the sideways force of someone (me at 250 lbs) sitting on the toilet when the boat is heeled or rolling. Other users have not reported problems in this area, which is why this is only a small concern.

So now the Airhead is operational. The brick of peat and the enzyme package are on the counter, ready for the first use of the toilet. Since I'm a regular guy, that should happen tomorrow morning.
Don't expect to see a report on how it went posted on this website.

No need to avert your eyes from this picture. That is just the crumbled up peat moss in the base of the toilet.

Learning To Live With Peat

Well, once again I failed to carefully read and follow instructions. As seen above I just crumbled the peat brick and placed it in the composting chamber before my first use of the toilet. The instructions clearly state that the peat must be moisturized before putting it in the toilet.
Without the moisture the peat does nothing to desiccate the waste, aid the composting and absorb the odors. After a few days of use the head had a very strong odor. The odor wasn't unbearable, but I had been told by the manufacturer and other users there is almost no odor from the toilet. I had expected only a very slight odor of peat. This definitely was not a slight odor, so something clearly was not working right.
After an exchange of emails with the manufacturer and re-reading the instructions I realized my error. I tried adding water to the composting chamber, but that did not seem to help much. I finally found a local source for the Sphagnum Peat bricks and I hydrated the brick in a Zip-Loc bag as shown in the picture on the left. This brick is only partially hydrated because it would expand beyond to capacity of the 1 gallon bag if fully hydrated.
So I just added a few handfuls of peat to the composting chamber and within minutes the odor had greatly diminished. By the next day the odor was completely gone. I will keep adding water to this bag adding more peat to the toilet until the entire brick is in the chamber.
It took me a few days to find a local source of the peat. The garden section in Walmart, Loew's and various hardware stores in my area do not carry these bricks. They do sell loose Peat Moss, but the smallest bag is 22 liters. I found a larger gardening/nursery supplies store, but when I asked for Cocoa Peat they couldn't find it in their catalogues. Browsing the store I found this brick of Sphagnum, which from Wikipedia I knew was Peat Moss. It was the only brick they had in the store.
After discovering how to use the brick and determining that it takes care of the odors, I used the Internet to find another source for this material. Through that research I learned several things.

Sphagnum Peat is largely a non renewable product. Although there are several sources that harvest the product in a manner to not destroy the bogs in which the peat grows, much of the product is just ripped out of the bogs and not replaced.
The alternative to Sphagnum is COIR, which is the cocoa peat that I was originally looking for. It is made from the dehydrated husks of coconuts and is a renewable source since only the fruit of the palm tree is harvested not the entire plant as is the case with Sphagnum.

So I've ordered several bricks of COIR from a gardening website (http://www.gardeners.com/) and will use that peat in the future.

Emptying the Airhead and Converting to COIR

After nearly 10 weeks of live aboard use I finally emptied the composting chamber, and this time recharged it with COIR instead of Sphagnum.
10 weeks seems to be pretty consistent with other live aboards' experiences. Several couples have reported they average a little less than 6 weeks to fill the chamber. I am the only user of my Airhead.
I probably could have gotten a couple of more weeks of use if I didn't have those large chunks of un-moisturized Sphagnum in the chamber because of my initial screw-up described above.
For the re-charge I had several bricks of COIR on hand. I'm still working my way through the logistics of handling the compost material, and I am still making mistakes. Prior to emptying the compost chamber I placed one of the bricks in a 1 gallon Zip-Loc and added a couple of cups of water. This caused the COIR to expand to the limits of the Zip-Loc and I could not moisturize all of it. I took handfuls of the moisturized material and placed it in the emptied chamber. This was a little messy as it is difficult to hold the crumbly material in one's hand without letting lots of little pieces sprinkle about the head compartment. I also was not able to place enough material in the chamber for satisfactory use. I was having to moisturize the COIR a little at a time. So after a couple of uses the COIR in the chamber was over-whelmed and I was getting an unpleasant odor out of the vent. In a few days I got all of the material from a single COIR brick into the chamber and the odor disappeared.

I've revised my method for preparing the COIR. I placed another brick in a dry-wall-type bucket and added about 1/2 gallon of water. The COIR absorbed the moisture within a few hours and expanded to about 2 gallons in volume. I then placed the moisturized material in two 1 gallon Zip-Loc bags (shown in the picture on the right. Now I have a full brick of material ready to add to the chamber on the next re-charge. I also have material to add if more COIR is required on the current tank cycle.
My initial impression of on the use of COIR in place of Sphagnum is fairly neutral. COIR seems to work as well as Sphagnum, but it is a little more messy to handle. Unless there is a problem with the current cycle I'll stay with COIR. Also shown in the picture are two spare bricks of COIR that I purchased from Gardner's Supply (link above).

Emptying the Urine Bottle

Much more frequently than the compost bin, the Urine Bottle must be emptied. While dumping the bottle overboard does not pollute (Urine is sterile - no bacteria) it is generally not something other people like to observe. When at a marina I could take the bottle into the toilets and pour it down a commode or urinal. However that is often a long trek and won't be greeted any more enthusiastically by other persons in the toilets than the folks having cocktails in the cockpit of the boat in the next slip.

So my normal procedure is to check the urine level (gauge shown in the picture on the left) each evening, after dark before going to bed. If the bottle is more than 75% full I dump it overboard.
Unfortunately the gauge, which is just vinyl hose, has become stained such that it is difficult to read the gauge. On more than one occasion I have checked the urine level before going to bed and decided it did not need to be dumped. The next morning I discovered that in fact the bottle was completely full. Now it's daylight and dumping the bottle overboard is a problem. I have a spare urine bottle for those incidents. It is very important to prevent the bottle from filling to the top. I let that happen just once. It is non-habit forming.
Recently (Dec, 2008) I spent a month in a Florida marina where my boat was located in front of a popular bar/restaurant. My boat was illuminated by the lights from the bar and the marina. This made peeing off the deck or dock a very public event until well after midnight. It had also turned cold early in Florida and peeing off the deck at 3:00AM wasn't all that appealing even without the audience. So for nearly a month I was using the Airhead for almost every pee. I discovered that by myself, I could fill the bottle in less than 4 days. So, then I didn't really need the gauge, I just emptied the bottle every third night.
FWIW, the urine level in the picture above is just barely on the bottom of the gauge.

After One Year

Well, I've been using the Airhead for over a year now. That included over 4 months anchored in the Bahamas with no choice of using a marina facility. Even when I've been berthed in a marina I've normally used the on board toilet, both because it is more convenient and to fully exercise the toilet and find any limitations.
Overall I'm very satisfied with the decision to go with a composting toilet in general and the Airhead in particular. There really haven't been any serious gotcha's. Oh, I've let the urine bottle overflow once or twice and my experimentation with how much COIR to use still goes on, but it has really worked as advertised. Even my friend Steve Angst who crewed for me on the way to the Bahamas last year and joined for a week in the Abacos felt it was a good choice.
There are several things I've learned in this year.

Always have a spare urine bottle on board. Without a functional (i.e., non-leaking) urine bottle the toilet is nearly non-operational. I purchased a spare before heading for the Bahamas. My fear was having to empty the bottle at sea and then dropping it overboard and watching it sink to the bottom of the ocean. Turns out the bottle can fail. The original bottle started to leak around the bottom sight tube fitting. It took awhile to figure where it was leaking in the mean time the toilet remained operational with the spare bottle in use. It looks like the elbow fitting has cracked. I contacted Geoff at Airhead and he said there had been problems with the elbow fittings cracking the threads molded into the bottle. I confirmed that the threads in the bottle wall were cracked (picture on the right), and he said the fix would be covered by the warranty.
Gnats! I did develop a large colony of gnats in the compost bin upon return from the Bahamas. Contacting Geoff at Airhead, he said this was likely because of odor. I probably need to use more COIR than I have been. The toilet has gasket seals, but flies and gnats can get in when the urine bottle is being emptied or during use. To kill the gnats Geoff recommended a thorough cleaning of the compost bin using boiling water. I didn't have a way to boil a large quantity of water so I just used a strong bleach solution and let the bin soak for about 12 hours. I re-filled the bin with more COIR than I've used in the past. There are still a few gnats hanging around, but not like before. The next time I empty the bin I'll use even more COIR (probably back to putting the whole brick in at once), but before that I'll go the boiling water route.
Don't try to stretch the time between compost bin emptying. As the bin gets full the composting process seems to be less effective. That's when the odors can start. For now I will empty the bin every 6 weeks even if it does not appear to be very full. COIR is cheap.