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So-called "composting" toilets

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Lee Panza
Captain

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USA
465 Posts

Initially Posted - 07/31/2017 : 21:48:24

As an alternate to plumbed heads with holding tanks, or porta-potties, the so-called "composting" toilets make a lot of sense for a Cat25. They take up less overall space than a pump-toilet with a separate holding thank, requiring no regular pump-outs and avoiding the smells that seem almost unavoidable in plumbed systems. Yet they also avoid the dismal chore of emptying the holding tank in a porta-potty.

The key to how they work is the design of the bowl, which directs the urine into one tank while the solids go into another tank. The solids tank contains a load of peat moss, cocoa fiber, or other natural matter containing a type of bacteria (which is widely found in natural environments) that overpowers the stink-producing bacteria and reduces the fecal matter without the smell. The stinky bacteria can thrive in a tank full of liquid, but they quickly lose potency and are overwhelmed within the pile of peat moss (important note: they are not killed-off, just rendered essentially dormant by the "good" bacteria that are better at competing for the nutrients in the biomass).

The urine simply accumulates in the pee tank, which is easier and far less onerous to periodically empty than a tank of sewage from a porta-potty. Dumping it in a bathroom or latrine somewhere is certainly recommended (I carry a second tank to double the time between disposal runs), but even dumping it over the side in open water causes far less health impact than dumping a tank full of fecal sludge (as I understand it, urine doesn't contain the harmful bacteria that live in our solid waste).

Within the solids tank the waste matter is reduced, largely by loss of its water content (desiccation) and to a lesser degree due to biological decomposition. The material is not truly composted, which would result in relatively safe fertilizer, because the composting process requires a higher level of heat than would be found in one of these toilets. In the middle of a compost pile or a true composter the decomposition activity produces heat and the surrounding material insulates it to allow the temperature to rise to the level required for conversion; periodically mixing the pile eventually allows it all to undergo the transformation. But the solids tank in one of these toilets doesn't have the capacity or the insulation to allow this to take place. That's why, when the solids tank is occasionally emptied, the contents should be properly disposed of so nobody could accidentally be exposed to the remaining "bad" bacteria.

The solids tank has a mixer inside, activated by a crank on the outside, that you turn after making a deposit to distribute the new load and expose it to the "good" bacteria to the the maximum extent. Two of the most popular brands include a vent hose and a small fan to continuously introduce fresh, oxygen-rich air into the solids tank (through screened inlet ports on the side of the tank) and to carry off the little bit of aroma produced. The smell is musty, like the decomposing matter on a forest floor, and so little is produced that another popular brand (C-Head) doesn't even provide a vent. Even very loose stool (ie. diarrhea) quickly desiccates and is rendered neutral.

These units all require the urine to be kept out of the solids tank (a few drops won't matter, but a bladder-full would make a difference). The bowls are designed to channel the urine to a drain toward the front, while a removable cover over the entrance to the solids tank is only opened when one sits down for a bowel movement. An optional method is to place one of those coffee filters, the type with the corrugated sides that form a cup, over the solids tank cover beforehand, and then only open the cover to let the load drop in. I think this might help if someone's not good about aiming into the open tank (I've had to do a little cleaning on occasion, so I think there may be merit to this approach, but I've never actually used a filter). A choice of toilet paper that readily decomposes is advisable (I use a brand highly recommended by Practical Sailor and readily available in at least one of the big chain drugstores in my area, Scott Extra Soft, but PS rated Scott Rapid Dissolve as superior).

I think this covers the basics. I'm happy to explain in greater detail, but I would first direct anyone who wants to learn more to the websites for the three most popular brands. They contain a wealth of information about these units and how to use them effectively. If you want to know how I installed mine in my Cat25, including how I ran the vent, or why I chose one brand over the others, that kind of info could be useful to share on this forum.

Air Head: http://airheadtoilet.com/
Nature's Head: http://www.natureshead.net/
C-Head: http://www.c-head.com/index.html

By the way, some people have created their own dry toilets on very low budgets. Their creations, and their experiences with them, are also available online.

Here's what my installation looks like:

The trouble with a destination - any destination, really - is that it interrupts The Journey.

Lee Panza
SR/SK #2134
San Francisco Bay
(Brisbane, CA)

Tomas Kruska
Admiral

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Czech Republic
522 Posts

Response Posted - 08/01/2017 : 01:46:47

Thanks Lee for that information.

I'm in touch with AirHead company, but there might be a problem with the height of the toilet in my head. I will doublecheck the dimensions.

You mentioned the forced ventilation. I'm thinking about routing the hose to the cockpit locker, but I have a diesel heater there too, so I'm thinking that the heater could intake some fumes back to the cabin?

Dalpol Phobos 21, 2013, Sole Mio, hull #27, current adventures - We sail Phobos 21

PO of Catalina C25, 1978, High Anxiety, hull #701, SR, FK, L-dinette, inboard diesel Volvo Penta MD2010C w/saildrive - more info

Stinkpotter
Master Marine Consultant

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Djibouti
9013 Posts

Response Posted - 08/01/2017 : 06:31:04

Nothing against composting, but for ease of use (during and after...), plumbing simplicity, and odor prevention, I'm very happy with the Sealand 711 the builder put into my $+!nkp*+. It's plumbed to the fresh water system, a deck pump-out fitting and vent. A $5 tip makes the pump-out boat operator happy, and my only activity (my idea) is to use a hose to spray some water directly into the tank to clean it during the final pump-out at the end of the season. I also drop a little antifreeze in for the winter, for any residual water. It's also extremely simple to operate for any passengers. At 9.5 gallons, it holds about double the largest portables.

I don't know how the dimensions of the tank would work in a C-25 head space, but my space isn't much different. The dimensions are here.

Dave Bristle
Association "Port Captain" for Mystic/Stonington CT
PO of 1985 C-25 SR/FK #5032 Passage, USCG "sixpack" (expired),
Now on Eastern 27 $+!nkp*+ Sarge

HerdOfTurtles
1st Mate

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USA
68 Posts

Response Posted - 08/01/2017 : 10:05:33

Stinkpotter, I like that style head you have.

Thinking about getting it, but not crazy about having to supply pressurized fresh water to it.

It's about the same cost as installing a manual head/holding tank and thru hulls which is kinda lame, and the bowl is directly over the stink so that's kinda lame, but not having to worry about thru hulls and pump seals leaking etc is quite nice.

1978 Standard Rig
Fin Keel
L-Dinette

Stinkpotter
Master Marine Consultant

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Djibouti
9013 Posts

Response Posted - 08/01/2017 : 12:40:45

quote:
Originally posted by HerdOfTurtles

...but not crazy about having to supply pressurized fresh water to it...

Ya, I guess I didn't mention that part... However, the same boat (which I had built) gave me my first demand water pump, and it's really nice! No more hand-pumping into the sink, I can connect a hose to the sink faucet, and the head is push-peddle simple. Pushing the peddle up puts some water in the bowl, and pushing it down flushes with a swirl. I keep the pump switched off at the panel except when needed--even though it switches itself off by pressure. It's especially helpful for emptying the tank (99%) and pulling antifreeze through the lines before winter. The set-up is perfect for me--not necessarily for everyone else.

Dave Bristle
Association "Port Captain" for Mystic/Stonington CT
PO of 1985 C-25 SR/FK #5032 Passage, USCG "sixpack" (expired),
Now on Eastern 27 $+!nkp*+ Sarge

Tomas Kruska
Admiral

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Czech Republic
522 Posts

Response Posted - 08/01/2017 : 13:01:01

That's nice Dave, but not every country is so developed to have many pumping stations :-)

bigelowp
Master Marine Consultant

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USA
1736 Posts

Response Posted - 08/02/2017 : 20:00:21

I have read much about the Air Head composting head. What I like is that for us occasional users, the solid waste seems to take care of itself and liquid is easy to deal with. Also the lower potential of smell. If I were going on constant long voyages I might not want the composting systems, but for the occasional it seems to be better than my history with smelly heads or low-volume ports-potties. All the reviews I have read are positive. However, does it really fit in our limited space?

Peter Bigelow
C-25 TR/FK #2092 Limerick
Rowayton, Ct
Port Captain: Rowayton/Norwalk/Darien CT

Edited by - bigelowp on 01/19/2018 20:08:36

pearson39b
1st Mate

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93 Posts

Response Posted - 01/18/2018 : 11:02:59

Please allow me to resurrect this thread to put in a vote for the C-Head, composting toilet. Another C-25 owner recommended it a couple of years ago, but it took me awhile to come around to getting one for my live-aboard boat, a 43' trawler.

When I finally did make the decision to remove one of my vacu-flush commodes and install the C-Head, it was on the basis of a lot of research and vacillation that was finally resolved by biting the bullet and just doing it. Turns out to be one of the best decisions I've made on this boat, and now I'm planning to do the same on my C-25 this summer.

I do, however, have to qualify the the decision on a couple of important points. First of all, the second head on this boat is still plumbed into the vacu-flush system and the holding tank. We use it for guests and only rarely, ourselves - probably not more than once a month. We also use the close-by marina facilities and the C-Head is mostly - but not exclusively - for urination.

The C-Head has four big advantages over the other two models, the Air-Head and Nature's Head. It's a lot cheaper, It's smaller, it doesn't have to be vented and it uses a non-proprietary urine container - a one gallon, readily available, plastic jug. For the composting medium, we use pine pellets that we get from a farm store that sells them for horse bedding. They're cheap and actually smell good!

I don't know if a composting head works for everyone, but it certainly does for the two of us. I wouldn't hesitate to use it if we were still cruising, or even weekend-only boaters. At this point I wouldn't even be concerned if it were the only head on the boat. I did leave the vacu-flush plumbing in place in case I decide to sell the boat and the new owner wants the old head, but I have no intention of putting it back for our purposes.

So, a year after installation I can report a better smelling boat, not having to take the boat to the pump-out station once a week and saving $100 a month for the alternative of mobile unit, pump-out fees. On that basis, putting one in the C-25 is an easy decision, and I'm happy to recommend it to whoever is interested in this option.

Sailor Jerry
C-25 "Sea Song"
1978, SK, Std.
Pepin, WI

Tomas Kruska
Admiral

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Czech Republic
522 Posts

Response Posted - 01/18/2018 : 13:42:11

Jerry,

I'm still thinking about this, as the classical porta-potty has to be maintained a lot, however Air Head is too big for our boat.

May I have a question, how long the solid waste bucket lasts when you put the toilet paper inside?
Or do you separate the toilet papers? Separating the papers might be a little problematic, since we have a very limited space in the head compartment, not speaking of some modesty issue for my wife ;-)

If you use it over the weekend and you plan to go back the next weekend, is it necessary to empty the bucket or you can leave it until full?

Thank you

pearson39b
1st Mate

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93 Posts

Response Posted - 01/18/2018 : 14:36:30

Tomas,

We're old Mexico cruisers, so we have been using a separate receptacle for TP for a long time. You only have to clear out a paper clog once to make that a lot easier to rationalize! Actually, I don't know if any of the composting toilets will let you throw the paper in the toilet because it will also foul up the churning mechanism, which is what eliminates the smell by covering up the feces. I understand the modesty issue. We use a small trash can with a hinged lid and composting plastic liner bags that we change frequently.

How often you change out the medium totally depends on the amount of usage and convenience. Because there's just two of us and we use it primarily for urine, we can go for a month between change-outs even though we live on the boat full-time.. With a family, you might do it weekly. I would suggest calling the C-Head business owner (he's easy to reach) and talk it over with him. He's a boater and extremely helpful on just these questions. He also has a good FAQ sheet available.

The one caution I would offer, is to make sure you do your measuring and pick the right model C-Head before you order. A friend of mine found out the hard way that it is very expensive to return one from California if it doesn't fit. It's the only negative about this product, but it's certainly worth mention.

Sailor Jerry
C-25 "Sea Song"
1978, SK, Std.
Pepin, WI

Lee Panza
Captain

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USA
465 Posts

Response Posted - 01/20/2018 : 12:57:59

I'll check back in on this, as you raised a couple of important questions, Tomas (although I see from your sig that you've downsized from your old Catalina 25).

First, as Jerry pointed out (and as I had mentioned in my original post to this thread) the C-head is not vented and it relies (at least initially) on coverage by the pith/peat medium to suppress the smell. I'm pretty sure, however, that after a relatively short time the fecal material loses its stink just from dessication and the action of the "good" bacteria in the medium. The AirHead and the Nature's Head both use an external cranking handle to turn-over the contents in the solids tank, so adding additional medium isn't generally necessary. Once the most recent deposit is buried the medium starts to deactivate the feces.

As for toilet paper, this was an ongoing topic of discussion sometime back in Latitude 38, with some cruisers saying they routinely put the used paper in a separate receptacle to avoid clogging the plumbing between the toilet and the holding tank. Others swear they have not found that to be necessary (although this brings to mind the old saying about there only being two kinds of sailors: those who have run aground and those that will).

In the AirHead or Nature's Head, the agitator serves to shred the paper if it is a type that's designed to disintegrate easily. Practical Sailor had done an evaluation on several brands of TP, and they found Scott Extra Soft to be one of the best for this. I've found that if I moisten the paper after use, with the spray bottle of water that I keep by the toilet, it shreds easily with a few cranks. This also helps keep the pith/peat medium sufficiently moist for the bacteria to thrive (NOTE: If the medium drys out too much, the bacterial action slows down, but the dessication of the feces is more effective; with too much moisture the opposite happens, so the manufacturers advise that you keep track of this. I suspect the same would be true for the C-head).

As a final word, I have been using my AirHead regularly for a year and a half now, day-sailing frequently and over-nighting occasionally, with an occasional guest as well, and I have not needed to add any more medium or empty the solids tank. At this rate it would be quite a few years before that might become necessary. I've had to empty the liquids tank quite a few times (using the toilet is easier than peeing over the side), but even this chore is so much, much easier than dumping the old porta-potty had been.

The trouble with a destination - any destination, really - is that it interrupts The Journey.

Lee Panza
SR/SK #2134
San Francisco Bay
(Brisbane, CA)

pearson39b
1st Mate

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93 Posts

Response Posted - 01/21/2018 : 21:48:04

Lee,
Glad you brought up the cranking / churning mechanism. Turns out this is a consideration with the different models of composting heads. My recollection is that both the Nature's Head and Air Head use a vertical churn in the solids tank, and the C-Head uses an horizontal churn at the bottom of the receptacle.

Now, this wouldn't seem like a big deal, but then again, it might be. The vertical churn mixes everything up and leaves some of the fecal matter exposed. The horizontal churning action of the C-Head sinks the fecal matter and covers it completely. They actually have a video representation on their website that replicates the process with a golf ball, or something like that. Several turns and it sinks out of sight.

So, you really have two different processes. One mixes everything up, the other simply buries it, and I think that's how C-Head gets away without a vent fan to blow the stink overboard - no stinky stuff exposed. Of course, it also means you have to change out the media more often. The drying and decomposition process just isn't as efficient in the C-Head so you really have to unload it more frequently.

I know this seems like a lot of attention to a sh***ty subject, but for those of us who spend a lot of time on our boats, it's probably proportionate to the amount of attention we devote to waste systems - one of the things they don't always tell you about when you're getting into sailing!

Sailor Jerry
C-25 "Sea Song"
1978, SK, Std.
Pepin, WI

Davy J
Master Marine Consultant

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USA
1511 Posts

Response Posted - 01/22/2018 : 05:42:54

I'll add a few comments to this in case anyone else might be considering one of these composters.

We added a Nature's Head composting toilet in December, we then took a 26 day trip through the Keys and Key West. Twenty one of those days at anchor. I still have not needed to empty the solids container.

With the original marine head we would have needed at least three pump-outs during that time. The real advantage however, is the water that we saved. I'm guessing 30 to 50 gallons of water would have been needed for flushing. Since we never flushed with saltwater we would have needed to carry that much extra freshwater.

As far as the Nature's Head unit, I think it might be a little too large to fit in a C25.

Edit to add: after looking a Lee Panza's photo the Nature's Head unit might actually fit.

Davy J

2005 Gemini 105Mc
PO 1987 C25 #5509 SR/SK
Tampa Bay

Edited by - Davy J on 01/22/2018 05:50:12

Erik Cornelison
Navigator

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USA
194 Posts

Response Posted - 01/22/2018 : 14:03:38

This thread got me interested for sure. Keep posting. If you can put paper down it I'm sold, if no paper down the hole probably not.

Erik Cornelison
6th Generation Professional Sailor, First Gen Submarine Sailor.
1986 Standard Rig SW. #5234

Davy J
Master Marine Consultant

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USA
1511 Posts

Response Posted - 01/22/2018 : 18:28:08

quote:
If you can put paper down it I'm sold, if no paper down the hole probably not.

Difficult to discuss without sounding strange............

Our procedure is to put the first "usage" of TP into the toilet. Subsequent "usages" of TP are put into a gallon sized freezer type bag, sealed and then disposed of into the regular trash.

Our trash can has a close-able lid, so it's not as bad as it sounds...........

Davy J

2005 Gemini 105Mc
PO 1987 C25 #5509 SR/SK
Tampa Bay

sethp001
Mainsheet C-25 Tech Editor

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814 Posts

Response Posted - 01/24/2018 : 11:13:25

A few years ago, I emailed the Air Head folks about getting one for my boat and received what seemed like a decent response, possibly of interest. (I'm glad I didn't mention the size of my boat.) The email exchange starts at the bottom.

On Aug 1, 2014, at 6:12 PM, Eos Design <airheadtoilet.com> wrote:

Seth,

I'm not confident that you would be happy with the result. There are a lot of variables here.

Best Wishes,

Geoff

On Fri, Aug 1, 2014 at 2:56 PM, Seth wrote:

The application is a sailing boat, primarily located inland in the mid-Atlantic. Users would be my wife, five children, ages 13, 11, 9, 6, and 3, and me.

Seth

On Aug 1, 2014, at 2:42 PM, Eos Design <airheadtoilet.com> wrote:

> Seth,
>
> Can you tell me a bit more about the usage. Where is this located? What type of installation? Will this be something you repeat annually?
>
> Geoff

> On Fri, Aug 1, 2014 at 12:57 PM, Seth wrote:

> Hello:
>
> Could one of your Airhead Toilets support 7 people for a week, presuming one solids use per day per person?
>
>
> Seth

Seth
"Outlier" 1987 Catalina 25 SR/SK/Traditional Interior #5541
"Zoo" 1977 Morgan Out Island 30
"Nomad" 1980 Prindle 16
"Lost" 1988 Catalina Capri 14.2 (sold - yay!)
"Marine Tex 1" Unknown Origin POS 8' Fiberglass Dinghy
https://whichsailboat.com/2014/07/27/catalina-25-review/

Edited by - sethp001 on 01/24/2018 11:14:22

Davy J
Master Marine Consultant

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USA
1511 Posts

Response Posted - 01/24/2018 : 17:32:07

quote:
Users would be my wife, five children, ages 13, 11, 9, 6, and 3, and me.

WAT............. Your marine head would need to be emptyied every 12 minutes...........

Davy J

2005 Gemini 105Mc
PO 1987 C25 #5509 SR/SK
Tampa Bay

odonnellryanc
Navigator

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108 Posts

Response Posted - 01/29/2018 : 10:06:38

Seth, I assume you didn't go with the composting head?

That's a lot of people for the C25! Good for you :) I get cramped with 4 adults!

sethp001
Mainsheet C-25 Tech Editor

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814 Posts

Response Posted - 02/03/2018 : 21:59:02

quote:
Originally posted by Davy J

quote:
Users would be my wife, five children, ages 13, 11, 9, 6, and 3, and me.

WAT............. Your marine head would need to be emptyied every 12 minutes...........

Haha!

sethp001
Mainsheet C-25 Tech Editor

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814 Posts

Response Posted - 02/03/2018 : 22:23:33

quote:
Originally posted by odonnellryanc

Seth, I assume you didn't go with the composting head?

That's a lot of people for the C25! Good for you :) I get cramped with 4 adults!

No, I didn't get one.

And thanks! The boat was perfect for us at first when we had three kids (8,6,and 4). They all fit in the v-berth. Now the children are 17, 15, 13, 10, and 7, making it cramped. I've spent the last few years sleeping in the cockpit, which is nice unless it rains. We can all sleep below if it rains, using every berth/settee. When we're underway, we encourage the kids to go forward on deck so the cockpit isn't cramped. Or I stand in the companionway while the older kids sail the boat.

My folks keep the kids for a week a few times each year. Then it's just my wife and I, which is great. We just bought a trailer for the boat, so am hoping we can take some trips to other sailing venues.

I guess when the kids are all grown, the C25 might be perfect for us again. Meanwhile, we picked up a Morgan Out Island 30, which we're refitting.

Edited by - sethp001 on 02/03/2018 22:42:02

Stinkpotter
Master Marine Consultant

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Djibouti
9013 Posts

Response Posted - 02/04/2018 : 10:01:43

quote:
Originally posted by sethp001

...Meanwhile, we picked up a Morgan Out Island 30, which we're refitting.

Still sounds pretty cozy for seven...

Dave Bristle
Association "Port Captain" for Mystic/Stonington CT
PO of 1985 C-25 SR/FK #5032 Passage, USCG "sixpack" (expired),
Now on Eastern 27 $+!nkp*+ Sarge

sethp001
Mainsheet C-25 Tech Editor

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814 Posts

Response Posted - 02/04/2018 : 23:18:16

quote:
Originally posted by Stinkpotter

quote:
Originally posted by sethp001

...Meanwhile, we picked up a Morgan Out Island 30, which we're refitting.
Still sounds pretty cozy for seven...

Well, maybe I'm poor or from Boston. Either way, it seems good to me.

Edited by - sethp001 on 02/04/2018 23:20:52

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