How Do You . . . Use a Composting Head?

Cruisers’ small talk invariably turns to boat projects, and everyone has their “best thing we ever did” change or upgrade.  Ours, hands down, was the replacing of our traditional marine head with a composting head.  It was one of the first major changes we made to Kestrel and one we enthusiastically recommend to every boater we meet.

Toilets on a boat are not a particularly romantic subject.  With a traditional marine head, you balance on a tiny, gnome-sized bowl to do your business.  Once done, you flush the head by pumping your waste through a hose into a container that’s somewhere on your boat.  Your waste sloshes around in there until you are able to pump it out at a dock; the pump out hose is attached to the waste deck fill, and your waste is sucked out.

Traditional marine heads have many drawbacks, in our opinion.  The primary one is that unless you are releasing your waste into the surrounding water, you are forced to come to a dock to pump out.  How frequently you do that is based on how big your holding tank is, but it could be every few days.  That really limits how long you can be “out there.” Another huge drawback is odor; heads, head hoses, and holding tanks stink even when they are working properly and not leaking.  A third drawback is maintenance and repair; the joker valve (the all-important valve that makes sure the flushed waste won’t make a surprise appearance in your head) is sensitive to acids like vinegar and disinfectants, so keeping a clean head is complicated.  The pump will need to be lubricated, and the joker valve will eventually need to be replaced, which is a poopy job (hahaha, see what I did there?).

All of this complication is avoided with the use of a composting head.  No pumpouts, no smelly holding tank or hoses, no parts to fail. We bought an Airhead; there are other brands of composting head available, but the Airhead fits our space the best.  We also like that it has a standard seat size like on a regular toilet.  It also has gaskets on the underside of the lid and the underside of the seat, which seals off the interior.

The composting head is made of four components:  the seat, the solids holding tank, the liquids holding tank, and the venting system.  All four components are removable from each other, which is how you clean and empty the head.

This picture comes courtesy of Airhead’s website at  Ours did not include a monarch butterfly, but you can see the seat, liquids tank on the front, solids tank in the back, and venting hose.

Composting heads do not use water and are sometimes called “dry” toilets.  The solids tank is filled about halfway with a medium and has a mixing apparatus attached to an external crank to agitate the medium and assist in the composting.  All different kinds of media can be used in the solids tank, from coconut coir to peat moss to wood shavings to sawdust.  We use coconut coir bricks that we purchase from Airhead; these bricks are used in gardening for amending soil.  They are perfect for us because they are highly compressed, which means easy to store and won’t spill.  They are also sterilized, which means no possibility of a gnat infestation.

The venting system is simple.  Air is drawn into the solids tank via a small screened port.  Air is drawn out of the solids tank via a hose that is attached to a DC computer fan blowing out of the boat through a mushroom vent in the deck.  We have smelled absolutely no odor from the head ever.

Using the compositing head is virtually identical to using a “regular” head on land.  You sit on the seat, and pee drains into a bottle on the front of the head.  You dump this liquids holding tank as frequently as necessary.  If you need to do number two, you open a trap door and make your deposit into the solids holding tank.  When you are all done, you close the trap door and give the external crank a turn to bury the deposit in the medium.

I never honestly thought I would write the phrase “pee holes” in this blog.

So the million dollar question is, how do you dump and clean the head? When we are both using the head full time, I dump it every three weeks.  The night before I am going to dump the head, I prepare the new coir.

These are the coir bricks we buy from Airhead.  I’ve marked the “saw here” line on one.

Airhead recommends filling the solids tank ½ full of medium, and that works out to 1 ¾ bricks.  Using a hacksaw, I cut one brick down to size and save the other ¼ for a later use.  I put the two bricks into a trash bag and put the bag in a bucket.  I use 8 cups of water per brick for rehydration, so for 1 ¾ bricks it works out to 14 cups of water.  I let the bricks rehydrate overnight.  The next morning I break them up with my hands into fluffy compost that is moist but not wet.

When it’s time to clean the head, I ready my supplies:

  • two compactor bags
  • two tall trash bags cut open into plastic “drop cloths”
  • cheap dishwashing gloves
  • disinfecting cleaner (I use Seventh Generation)
  • paper towels—some full and others cut into halves and quarters
  • pot full of boiling water

Then it’s time to get to work.  It takes me about 45 minutes to clean the head from beginning to end.

I put trash bag drop cloths on the cockpit floor and on the settees. Glove up. Remove the entire head and place it on the cockpit floor.

Remove the seat portion and put it on the bag-covered settee. That gets cleaned second.

Dump the contents of the solids tank into a compactor bag, and then double bag it with another compactor bag. Don’t want that to spill! (To answer your question, no, it’s not gross.  It’s not a port-a-potty, so it’s not a bunch of poop sloshing around.  It looks and smells like mulch.  Yes, you’ll see some toilet paper, but it’s not just a big bucket full of poo.)

Clean the solids tank using the disinfecting cleaner and plenty of paper towels. I get it spotless every time, and that way I don’t have to work as hard next time.

Clean as a whistle.

Clean the seat portion with disinfecting cleaner and paper towels, getting all nooks and crannies.

The underside of the seat is the most complicated place to clean.  The air intake is the black port on the left, and the vent hose comes out of the grey coupling on the right.

Put the fluffy new coir in the solids holding tank.

Crumbled up coir, ready for business.

Put the seat section back on.

Reinstall the toilet in the head.

Boil a pot full of water and pour it in the liquids holding tank. Swish and let it sit for as long as you want. Usually I leave it for about 15 minutes.  Pour out the water and reinstall the liquids tank.

After three+ years of using the composting head, we still love it.  We love the freedom it gives us.  We love that it’s clean and self-contained.  We love that it’s environmentally friendly.  And mostly, we love that we don’t have to worry about it breaking, clogging, springing a leak, or otherwise making a good day . . . crappy!