Toilets: Composting & Otherwise [Updated Sep-2017]

Like many homes, we have two heads [restrooms...] 

And, like many boaters, we will use the term Head interchangeably to mean restroom and/or toilet- just to see if you are paying attention... [and because the composting toilet we chose is branded the Nature's Head...] Additionally, we will use the word toilet just to reinforce these inconsistencies... [We may even toss in some arcane references for either as well...]

When we bought the boat, each head [water closet...] had a very reliable Lavac toilet

You can pump a bag of small potatoes mixed with ping pong balls through one of these without issue... [But yet, we have stories, and those involved shall forever remain anonymous...]

And like a recreational vehicle [RV] (and many places people backpack these days) you get the pleasure of carrying everything with you; what you brought as well as all associated by-product(s)...

This means we have the privilege of sleeping above a 50 gallon tank designated for human effluvia [Our cats haven't figured out the Lavac... yet...]

Would you still want to sleep in our cabin?

We have also thought of many, more desirable cargos to stow under our berth [thereby averting the inevitable...]  So some day we may get a 2nd Nature's Head... [Hopefully before the aforementioned occurs...]

Like when we RV, we have found it very tough relying on 3rd party pump-out stations [availability, functionality, inconvenience, etc.] Fortunately, unlike an RV, we also have the option of emptying the toilets and/or contents of their holding tanks into the sea when in areas where that is allowed [i.e., legal...]

Sidebar: I've witnessed seals evacuate underwater... I can assure you ink from squid and octopi, and human excrement pale in comparison... Not to mention whales: the Humpbacks in our region can purportedly gulp 1.5 tons of herring in one mouthful. [Talk about super-sizing...] We would have to digest 8.2 lbs of herring each day between us to consume that much in a year! [...If you catch my drift... Ain't happening...] 
Design Notes: I have re-plumbed the Lavac in our aft head [with holding tank]. The new approach uses one pump [electric, non-macerating i.e., quiet- with manual back-up] to flush the toilet and, with the flip of a Y-valve, empty the holding tank overboard. This obviates one through-hull; the one dedicated to the current macerator pump that empties the holding tank, as the new set-up shares one [existing] through-hull for both toilet flushing and holding tank emptying... Of course, as required by the USCG, the holding tank can still be emptied through the deck fitting using a pump-out facility. 
Related to this discussion is why we decided to replace one of our two Lavac toilets with a composting [desiccating] Nature's Head unit. This was done in July-2015, and our preliminary [and ongoing...] impressions are very favorable- as are those of our guests... [More on that, below...] 

We now have have the option of using the Lavac [which has fresh or raw water (i.e., the water the boat is floating in...) flushing] and pumping overboard or to the holding tank- which can then be emptied overboard when at sea or pumped-out as appropriate...

Or we can use the Nature's Head [composting toilet (desiccating really)], which is legal to use anywhere worldwide, and is also the primary guest head. 

Yes, we have diminished some opportunities [and associated methods] some might employ for decommissioning toilets... 

Real-world testing was completed shortly after commissioning the unit: we had a family of 6 onboard for 8 days... [2 adults; 4 female offspring ranging from pre-teen to painful teen...] While they were welcome to use either head, they chose to mostly [95+%] use the Nature's Head and it handled them very well. [When polled individually, 'no pumping' was cited as their primary decision factor...] 

Design Note: I plan to plumb the liquid capture directly to the old holding tank for that head- eliminating the need for the built-in liquid container, and emptying it...

What about smell? Won't that make me seasick? After all, I have used an outhouse before... 

This isn't the anything like that... absolutely no bathroom odors... sorry...

What about emptying it and maintenance? 

We empty the solids bin about once a month with full time use by two adults...  Of course this period is extended with part-time use...

Watch the following videos, and if you are interested, we have a section regarding consumables and maintenance after the videos.

Liquid Separating Composting Toilet

The Big and Dirty Questions about These Toilets

Tips, Tricks and Solving Problems

Consumables and Maintenance:
We get 8+ months of usage out of one of these coconut coir [shredded coconut husk] bricks. [US$16 including shipping in the US = ~US$2/month on average for 2 adults full time...] 

We have also seen coir in box stores like Home Depot, Walmart and the like for reasonable prices...

This particular coir is finely chopped and therefore easily converts to peat moss-like consistency when hydrated without much effort. [Vs. longer strands of coconut fiber which are slightly more difficult to break-up and also get wrapped around the agitator rods and increase stirring friction...

Basically... using ~1 cubic foot of storage space on the boat [3 of the above bricks] we can carry enough coconut coir to accommodate 2 adults full time for 2 years at a cost of ~US$50/2 years. Hard to beat. Priceless when you consider I didn't have to empty a holding tank umpteen times [or carry liquid effluvia around with us...] during that same period...

That 1 cu ft of coir will actually last us 3-4 years since we alternate between the Nature's Head and the flush toilet depending upon circumstances and location, and whether we have guests [who so far all prefer the Nature's Head because "...they don't have to pump it..."]

This particular coir brick is about 1 ft square and is composed of 4- ~1 in thick layers. I separate the 1 in slabs with a small pry bar or kitchen spatula and store them in a waterproof sack. 
To recharge the toilet with coir, I drop the half-slab into a large ziplock bag [e.g., 2 gallon bag] and add about 3-5+ quarts of warm water to hydrate it. Within 30-60 mins I can break the remaining clumps up while in the closed bag, add more water [or coir if too wet...] if needed, and then pour it into the recently emptied solids chamber. Done.
With practice, all this takes maybe 15-20 mins of hands-on time, including clean-up and putting things away, and disposing of the sealed bag of effluvia [er... future compost...]

Remember we also have a 2nd head with a Lavac [water flush] toilet, so we actually go quite a bit longer between recharges on the Nature's Head. [6-12 weeks when it is just the 2 of us- depending circumstances and where we are...] While the Lavac has the traditional holding tank set-up, since we have the Nature's Head, we only use the Lavac when we can discharge overboard, thus eliminating the pump-out sessions...

Like with all things of this nature, YMMV... 

Additional Resources:

  • Composting Head Manufacturers [Units that separate liquids from solids. Very important!]
    • Nature's Head [The one we went with]
    • Air Head [The original and a very nice unit also]
    • C-Head [Well designed smaller unit. So far this is the only one that could fit in our camper, so we may be getting one...]
    • Separette [Beautiful design; we are putting one in our cabin- as have several friends who love theirs...]
  • Articles from other owners/users:
    • The Boat Galley [Lessons learned their first 8 months with a new Nature's Head in a tropical climate]

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