Toilets: Composting & Otherwise [Updated Mar-2019]

  ➛ ➛ From our list of Stuff we have and use [and do...] in the right sidebar ➛ ➛   


This is part of a series describing some of our common boat systems and their operation. 


We refer to these often not only for our own use, but also when asked specific questions about systems on Denali Rose, and when participating in discussions on various forums.

We aren't implying our choices are the best or only way to go; they just happen to be the decisions we made [...or sometimes what came with our boat...] 


We also include relevant, qualified links to external resources on the topic.


———— Latest revision: 21-Mar-2019 [by Bill] ————


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 wonderful Lavac toilets with a composting [desiccating] Nature's Head unit. 

We did so 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...

Note: Bad smells are absolutely possible and do happen if urine is accidentally added to the solids tank. Thankfully, this is rare, and not instantaneous... [This is the primary reason outhouses smell...]

What about emptying it and maintenance? [i.e., Reality...]

We empty the solids bin about every 3-4 weeks with full time use by two adults...  Of course this period is extended with part-time use...


The urine jug gets emptied every day or few days depending upon use. [Occasionally guests seem to have a difficult time noticing when it is full... Thankfully, any overflow goes onto a shower floor and can be rinsed into a drain...]

The full jug can be odiferous when emptying it. The manufacturers of this type of head recomend adding a little sugar or vinegar to the jug when empty. In our experience, neither works well enough to prevent odors when emptying, or the slow build-up of scale inside the jug.

Experiments lead us to try Oxyclean powder [unscented...] since we have it onhand for laundry. We add ~ 1/2 tsp to the jug after emptying and rinsing. There are absolutely NO odors, and no scale build-up. [The first application will remove residual odors and scale as well.]

Carolyn of The Boat Galley recommends Urine Digester [a bio-enzymatic 'cleaner'...] 


For many more details about the Nature's Head, watch the following videos. [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$20 including shipping in the US = ~US$2.50/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. [Compared to 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$60/2 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. We 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, we 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 you 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...


To keep the urine container odor and scale free, we use Oxyclean powder. [unscented...] We add ~ 1/2 tsp to the jug after emptying and rinsing. There are absolutely NO odors, and no scale build-up. [The first application will remove residual odors and scale as well.]

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:

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