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Air Head Composting Toilet

March 4, 2013

While debating a return to the continent after nearly 6 years in the Caribbean, we tried to imagine necessary changes to our lives. Since our first stop was to be a few months in Marathon, Florida, we narrowed our internet search to the Keys, which is where we first heard of their no-discharge laws. In order to ease (and verify) compliance, a pumpout boat makes its rounds in Boat Key Harbor and each boat is expected to give an appropriate donation from their holding tank. Boaters who fail to do so on a weekly basis are fined and can be expelled from the harbor.


The kit

No-discharge laws have been in place in the Great Lakes for years and many States are implementing similar laws. We recently read that in North Carolina boaters are required to maintain a pumpout log, documenting timely pumpouts depending on the amount of time spent onboard. With the increase in regulations and their enforcement, it was obviously time for us to find a more legal solution than our bucket.

We had been using a bucket for 5 years, since we removed the marine head, holding talk, Y valve, various hoses, fittings and thru hulls and fiberglassed the two now unnecessary holes in the hull. Unwilling to lose all we had gained by such a change, we searched for a different way. (Advantages to a bucket include: less space required, no hoses to leak or smell, no thru hulls, no hose clamps to cut you as you clean, and best of all, no rebuild is ever necessary.)


The inverted bowl

Our solution was an Air Head composting toilet. It meets all no-discharge laws without the space and fuss of holding tanks and pumpouts. We had investigated the Air Head when we switched to a bucket, but at that time there were five of us onboard, and we were told it would not compost as quickly as we would fill it. Now, with two boys in college, it was a more viable option.

Before ordering one, we had to be sure it would fit in the space designated for a toilet in our head. At www.airheadtoilet.com the Air Head is shown to be 17.5" fore and aft, 18.44" side to side including the crank handle and 19.25" tall. These dimensions do not tell the whole story, however. The crank handle (to stir the compost) must have room for a complete revolution; the household sized toilet seat sticks out the back an additional 2"; and there must be room for a fitting to attach the ventilation hose to the unit. Since space was an issue with us, we ordered (free) a handle that accommodates a 3/8" drive ratcheting wrench handle so that very little room is required to "stir" a complete revolution. We also requested a marine sized toilet seat (free) to save the 2" in the back. When ordering, you must specify a right or left hand crank. This is determined as you stand in front of and look at the Air Head. The exhaust hose will be on the side of the unit near the back, making it another variable to consider. The most difficult part of the entire process was paying for it: $1100 with tax and shipping and 5 feet of extra exhaust hose. But with so few moving parts and a 2 year warranty, we hope this is the last time we have to invest this much money in a marine sanitation device.


The fan in the dorade before it was wired

The Air Head arrived complete with: the wrench handle adapter and marine sized seat we had requested (including rubber gaskets on the seat and lid to decrease odor in the boat), 10' of exhaust hose, a rubber hose fitting, a 12 volt fan in a shroud, a removable liquid tank with cover, a lid for use when transporting the solids tank, mounting hardware, one block of coconut fiber starter peat, a few tablespoons of enzymes, 50 bowl liners (we call "deposit slips") and instructions. I was disappointed by the fact that the exterior of the unit is textured, meaning it holds dirt and is harder to clean. Air Head redeemed themselves though by making the inside of the bowl exceptionally smooth and therefore easy to keep clean.


The installed unit

Installing the Air Head is a simple matter of a few hours. The base is attached to two brackets that are screwed onto the platform where the head will sit. The rubber hose fitting attaches to the base of the head at one end and the exhaust fan at the other. We chose to attach the fan under the Dorade vent, since that meant there was no need to drill another hole in the deck. Dave connected the hose to the shroud around the fan and then attached the shroud to the headliner under the Dorade vent already in place. If no Dorade is available, some sort of exterior vent or cover must be installed. A passive vent is Air Head's recommendation, though you could also use a Nicro solar vent. So far, our installation in the Dorade has been sufficient. We are sure to keep the vent facing away from the wind so that it does not counteract the fan. Total installation time: 8 hours including two trips to the hardware store which added $40 to the cost of the head.


The installed vent hose

Now we were ready to prepare our Air Head for use. Following the instructions, we placed the coconut fiber (as an alternative to peat moss) brick provided in the solids tank, added 2 quarts of water and let it sit overnight. After it absorbed the water, the peat moss was easily stirred with the crank handle. Be sure to close the trap door to the solids tank (We call it the "deposit box.") because the contents tend to fling as you stir. Next, we stirred in the package of enzymes, also included. Additional enzymes for after each emptying of the tank can be bought at hardware stores. It is used for maintaining septic system health. One brand is Drain Care. The liquid tank is prepared for use after each emptying by pouring in 1/2 to 3/4 cup of sugar. This reduces the odor during emptying.


Removing the liquids container

As with any marine head, when we have guests aboard we must have a toilet etiquette class. Because the system works best when as little liquid as possible is put in the solids tank, we recommend that everyone sit. This has always been the rule offshore anyway; it is safest, cleanest and ensures that liquids are kept separate. When making a deposit, place a deposit slip (coffee filter) over the trapdoor, provide donation, depress the lever for the trapdoor and the deposit falls in. Close the trapdoor and turn the handle to stir and bury the deposit in the compost. As an alternative, you can make a direct deposit with the trap door open, in which case no deposit slip is necessary. This is not recommended for liveaboards or for rough weather usage because it leaves the deposit box opened for too long. Since a weekender's unit will have more time to compost, Air Head says toilet paper may be placed in the solids tank as well, but again, this is not recommended for liveaboards.


Deposit slip in place

Now what? After a few days of use or before leaving your boat for any length of time, empty the liquids bottle. There is a clear hose that allows you to see the liquid level and gives you an idea of when it needs to be emptied. Unscrew the two attachments, slide the bottle out the front, attach the lid and take it to any toilet to empty. The bottle is discreet and weighs only 12 pounds when full. Before reattaching the tank, rinse with a little vinegar and hot water then add the sugar.

Since the solids compress as they decompose, the longer the contents stay in the deposit box the more times it can be used before it needs to be emptied. Weekenders can make about 80 deposits, liveaboards about 60. When the time comes to empty the tank, you have a few options. If the contents have been sitting for a minimum of three months it has completely composted and can be trenched into soil in most areas. (Check local regulations.) Otherwise, the contents can be emptied into a trash bag and thrown away. This is completely legal. It is also legal to empty the solids tank into a composting toilet, often available at National Parks. Offshore the tank can be dumped over the side. For liveaboards, since the contents will not be completely composted by the time it fills, a second solids tank is recommended. Simply cap the full one and store until composted. It is 12" in diameter and 11" high.


The hose is barely visible

After emptying the solids tank it is best not to clean it. In the presence of the peat and with the air flow through the deposit box, non-odorous aerobic bacteria have grown and some of them will still be present in what remains in the tank. These are the good bacteria, as opposed to the stinky anaerobic bacteria. Urine inhibits all bacterial growth – another reason to be careful to keep it separate.

The bowl itself can be cleaned with any non-abrasive, non-chlorine, hard surface cleaner. In order to ensure we do not introduce any cleaner into the deposit box and disrupt the growth of the good bacteria, we use cleaning wipes.

It is recommended that you clean the screen on the fan every few months. At first we simply eliminated the screen since its purpose is to keep out bugs and we don't have screens in our Dorades anyway. Then we realized that the bugs we were trying to keep out were what we have come to call "pooh flies" and only a screen on the vent will prevent them.

We had been warned by other users of composting toilets that getting them "primed" is tricky, so we were not surprised by the smell wafting from the Dorade by day three. We thought maybe our "good" bacteria needed more time to grow, so we waited. Finally, after a week, I reread the instructions to see what we had done wrong. There it was, in two different places: our solution. Though we had been provided with only one brick of peat, liveaboards should start with two. "The more you use the unit the more moisture is in the solid tank. Adding peat has a surprising drying effect. When in doubt add more peat moss." We purchased another brick, and within hours of adding it to the tank the smell was mostly eliminated. Peat can be purchased at most gardening centers, but we prefer the coconut fibers from Air Head.

For weekenders I would recommend the Air Head composting toilet without reservation. Liveaboards, however, must consider several factors before deciding if it is right for them. How many people are on board? Air Head does not recommend fulltime use for more than three people. How strict are the laws in your area? With the increase in both regulations and their enforcement, a composting toilet may soon be the only option in some areas. For the price, ease of installation and peace of mind knowing we are legal even in no-discharge zones, the Air Head composting toilet is, for us, the next best thing to a bucket.

Previously published in Good Old Boat Magazine

MONDAY we'll talk about how to deal with four-legged critters onboard.

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