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Old 02-06-2013, 00:19   #1
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Self Designed Large Capacity Compost Head

This is a thread describing my home-made composting head. I have been asked several times for more details, pictures, etc. This ISN'T a thread about whether YOU should have a composter. There are many, MANY threads debating the pros and cons, and I would respectfully ask those who oppose composters to refrain from posting here, since this is a thread for people who ARE interested in composting heads. Since it's a foregone conclusion that some will chose to point out why they don't like composters, I would also ask those who are here to discuss the thread's subject to just ignore comments not related to that, it'll be a nicer time for all .

So the first question would be why build your own? In my case, the driving force was crew size. My entire boat was designed around a crew of 5, specifically my family. So I had to plan around that, 5 people using the head for short (2 month max) cruises, though we mostly do day sailing and 4 or 5 day trips. The commercial composting heads out there (Air-head, C-head, and Nature's Head) Are good for about a month of full time use for a couple. I would need 2 to get a reasonable time between emptying.

Cost is always an issue for me, I'm one of those people who really can't afford to own a large cruising boat. My 32 foot catamaran cost about $8000 so far, including the brand new engine, so you can see where the cost really matters to me. I have $200 in my toilet system. Commercial compost units cost $500 to $1000 (which I think they are well worth, I have examined all 3 and they are very well made), and a new install of a "normal" system, by my estimate, would be over $1000.

Finally, I just prefer to do things myself. I enjoy the process, from concept to design to production...and finally use. Sailing a boat I designed and built is great fun, and using a toilet of my own design is...well ok not "fun"...maybe gratifying? Anyway, it's cool.

The concept of a compost toilet is simple: Separate the liquid waste from the solid waste, mix the solid waste with the organic matter to expose it to oxygen and thus kill the odor causing anaerobic bacteria, dispose of the urine in an appropriate manner, and empty the solids when they get high in the container.

What I have is an entire boat built of plywood, so that is the starting point. The head is a bit over 3 foot wide at the back, and 5 feet deep. It's quite spacious as small boat heads go. There is essentially a "shelf" cross the whole back of the head with the toilet off to the side. This allowed me to put a shelving unit to the other side, and lots of room under for material storage and the urine collector.

The seat and urine diverter is from a company called Ecovita http://www.ecovita.net/products.html , specifically the "Privy 500" unit. Cost is $100. This seemed steep to me, but it's the only thing I could find. Once it arrived (very slow shipping) I was pleased with the product. It's very stout and looks quite nice, with no sharp corners that would make cleaning difficult.

My storage container of choice is an Igloo Cube cooler. The size is 12 gallons, compared to 5-ish on the other units. The height is perfect as is the square shape, and it was free since I had 2 that were collecting dust. A large 15 gal round plastic container from Home Depot was a close runner up at $5.95.

One thing I did different was add a 3/4 inch 3-way valve I found on Amazon to the urine diverter. This allows the urine to be directed overboard when it is appropriate. Normally the urine is directed into a 2.5 gal container. I spent a lot of time in the PVC section at Home Depot getting the parts just right. My only thru-hull on the entire boat is an above-the-waterline drain that catches the 2 sinks and finally the urine before going overboard.

My organic matter of choice is pine shavings. I don't use Peat Moss because I've read that the peat bogs are destroyed when it is harvested, and because some have said the "small black flies" that sometimes plague composting toilets can come from the peat. I tried Coconut coir, ground coconut husks, but I didn't like the results. You use a good amount of water to "make" the brick into useable material, and I believe that moisture may have been the cause of the musty odor I had while it was in use. I buy large bales of pine shavings at Wal-Mart for around $10, lasts a long time and smells nice. But then I build with pine so I may be biased on the smell.

Finally, I don't have a mixer in my toilet. As you use the dry side, you cover your business with the pine shavings. This works just as well and makes the construction much simpler. But it does lead to occasional bits of the pine ending up about the head. That is rare now that I have made it clear to my crew it is NOT ok and clean it up if you make a mess.

The only electrical part of the unit is the fan. This removes the moisture, and is an important part of the system. I used a computer fan from an old desktop I had and fit it to PVC parts. I did use the head without it for the winter, but in summer heat you'll get lots of condensation without it.

It's been in use in its current form since September and on my previous boat in a smaller "prototype" for a couple years. It was used full time for the month of April, and lots of day and weekend sailing since Sept. It has absolutely zero odors (except the afor mentioned musty smell from the coconut coir). It's good for 3 weeks or a month full time, and I have no idea how long for day sails and weekends, I change it every couple of months. This design is the result of lots of reading and a couple years and several versions, and I wouldn't change anything right now if I started over.

Edit....in the picture of the 3-way valve, the fitting pointed at the camera goes to the urine container when in use.
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Old 02-06-2013, 02:26   #2
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Re: Self designed large capacity Compost head

Nicely done. When I first read your abbreviated thread title, I thought it was about guns
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Old 02-06-2013, 02:51   #3
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Re: Self designed large capacity Compost head

excellent!
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Old 02-06-2013, 04:46   #4
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Re: Self designed large capacity Compost head

Thanks Gordo, Cool looking cat you have there. And the toilet looks nice and simple. one thing I have been wondering about was how to make one thats knockdown proof. Probably the least of your worries if it ever happens to your cat, but us poor folk on our tippy mono's have to think of things like this! I guess I would just need to keep the lid for the container and fasten it in place for nasty weather. And make sure the urine is pumped overboard after use.

Another question is about the consistency of the dried turds (for want of a better word) my guess is that they would float, making disposal well offshore important. and they would not be easy to pour down a normal toilet like a chemical toilet can so really they would need burial someplace or disposal in a handy longdrop toilet? I guess I personally would be happy taking them well inshore and digging a hole to bury them. What about toilet paper?

This is all getting close to home because our local EPA (bless them!) in tassie has just declared it will start prosecution for any breach of its rules regarding sewage this means that sewage cannot be released from a boat inside state waters anywhere (ironic since the local councils regularly dump raw sewage in from their overloaded and undermaintained systems everytime it rains). So the only place to dump a holding tank is now outside state waters which is something like 25 nautical miles to sea from hobart in the full force of the wild southern ocean. With luck they will amend the regs to make it more practical but until then everytime we wee into the ocean we are at risk of a fine.

Cheers

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Old 02-06-2013, 06:28   #5
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My dry stuff goes into the dumpster. Any argument on that subject is moot when one compares dried feces with children disposable diapers. Our volume is practically zero compared, and since it's already breaking down it won't last any time in a landfill. God only knows how long pampers last!

As far as consistency, its all basically like dirt, especially when it sits for a couple months. The bottom parts, ie oldest, have no form of the original stool at all. if you wanted to be ultimately proper, you could simply set it aside and let it continue composting like the C-head people recommend.
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Old 02-06-2013, 06:46   #6
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Re: Self designed large capacity Compost head

Nice set-up. We just installed an Airhead and put in a diverter and pump for the urine container to pump it into the old holding tank. This allows us to dump the urine much less frequently and we can go off-shore to do it. It works really well.

So far, we prefer the coconut coir because it stores in compact bricks. Turns out we can find it at a local pet store as it is used for hamster cages and such.
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Old 02-06-2013, 08:20   #7
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pirate Re: Self designed large capacity Compost head

I lament the passing of bucket and chuck it but it wasn't all that pleasant, visually. And gone is the ease of pooping and pumping inshore.

However, the holding tank, permeable hoses and the pumpout hassle if not in a marina will not be missed.

I had wondered if the stirrer/aerator was essential.

Also, on the pathogen discussion, younger readers may not know about Milorganite, a fertilizer made from dried human poop. Available at the big box stores, this has been heat treated, and apparently is OK for use on food crops. And, of course, less civilized folk have been using "night soil" for millennia.

Poop Pot Opera: The day will come I bet when some city father realizes we're dumping dried human poop in dumpsters. The powers that be aren't going to like that.


Thanks Gordo. Love the use of simple stuff. I was going to skip the $100 seat. Have to rethink that.


Milorganite - Wikipedia, the free encyclopedia
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Old 07-06-2013, 14:36   #8
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Re: Self designed large capacity Compost head

[QUOTE=Blue Crab;1250373]I lament the passing of bucket and chuck it but it wasn't all that pleasant, visually. And gone is the ease of pooping and pumping inshore.

However, the holding tank, permeable hoses and the pumpout hassle if not in a marina will not be missed.
/QUOTE]

Here is my "bucket and chuck it" DIY composting toilet. It cost $18 for the padded toilet seat at Wal-Mart but the rest was made from marine plywood scraps and an old bucket. Most DIY off the grid cabin based composting toilets don't bother to separate urine and solids, with this set up (and a nearby unlimited supply of free sawdust from a guy that builds cabinets) I can just pitch the garbage bag every two weeks and put a fresh one in with more sawdust. If you are worried about spillage (not really a problem) while underway the bucket lid can be attached and removed when needed in 15 seconds as there are no fasteners except a little butyl tape to make the top panel feel solid as granite. It is key to cut the pieces precisely so they fit together like a puzzle.

It took about two hours to design and build, and can be broken down completely in about thirty seconds, but so far no cleaning has been needed. In the second photo you can see the missing panel that the toilet seat is attached to. There is extra storage around the bucket and the bucket could be deleted if a larger storage bin is desired. Even the interior designer finicky girlfriend doesn't mind it, especially since there is no odor and no "noises" to worry about. Overall I am completely happy with the project and I think it looks better, is simpler and easier to maintain than the non- DIY expensive products. Also, it is easy to use this design to fit the available space without wasting any space.
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Old 07-06-2013, 23:29   #9
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pirate Re: Self designed large capacity Compost head

" Most DIY off the grid cabin based composting toilets don't bother to separate urine and solids, with this set up (and a nearby unlimited supply of free sawdust from a guy that builds cabinets) I can just pitch the garbage bag every two weeks and put a fresh one in with more sawdust. "

I'm reading everywhere separation is critical.

I have a pal who lives in a MH, at the edge of the forest. He dumps grey water and black water and the next day you can't smell it.
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Old 08-06-2013, 04:10   #10
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Re: Self designed large capacity Compost head

I was wondering about your venting. Do you have any concerns about the longevity of the computer fan on your vent? I know they're inexpensive, is your fan an easy to replace installation? Also, do you have to filter the vent, charcoal filter or something similar?
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Old 08-06-2013, 05:58   #11
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I wish I could have been there when the Home Depot guy asked if he could help you with the pvc parts. Ah boaters, only we understand the thrill and fascination of this toilet stuff. I still fondly remember the deep sense of well being and accomplishment when I flushed for the first time after rebuilding the Jabsco.
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Old 08-06-2013, 06:42   #12
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Re: Self designed large capacity Compost head

Quote:
I was wondering about your venting. Do you have any concerns about the longevity of the computer fan on your vent? I know they're inexpensive, is your fan an easy to replace installation? Also, do you have to filter the vent, charcoal filter or something similar?
I purchased an AirHead in 2005 and the vent uses a standard small computer fan. Seawater shorted mine out and I replaced it with a standard one from Radio Shack that has been running continuously since 2006. They are very durable and burn very little power. I leave it running all the time, and I keep the door to the head propped open when away from the boat so the little fan helps to pull air through the cabin. Very effective at keeping the boat smelling good and the air inside fresh.

One big advantage of separating the urine is you vastly extend the time between required dumpings, and the material you dump is much better composted and drier. I personally would be very reluctant to dump a mixture of both into a dumpster ashore. Also, I wonder what the sawdust would do if you were disposing of it in a standard porta pottie dumping station ashore?
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Old 08-06-2013, 08:31   #13
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Re: Self designed large capacity Compost head

Quote:
Originally Posted by ElGatoGordo View Post
....My storage container of choice is an Igloo Cube cooler. The size is 12 gallons, compared to 5-ish on the other units. The height is perfect as is the square shape, and it was free since I had 2 that were collecting dust.....
Gato, thank you for sharing. You did a good job.
Would you be kind to provide the cooler measurements? Just to get an idea of the space taken by a 12 gallon container. Space is critical for me and I need to plan the footprint carefully.
Other questions: the plastic lining the cooler - wouldn't it stain or discolor? They say that we should not clean the container after dumping so not to get rid of the "good" bacteria, do you clean yours?
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Old 08-06-2013, 20:40   #14
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pirate Re: Self designed large capacity Compost head

Quote:
Originally Posted by kthoennes View Post
I wish I could have been there when the Home Depot guy asked if he could help you with the pvc parts. Ah boaters, only we understand the thrill and fascination of this toilet stuff. I still fondly remember the deep sense of well being and accomplishment when I flushed for the first time after rebuilding the Jabsco.
What an excellent post, sir. When they ask, I always think "if only you could help."
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Old 12-06-2013, 16:26   #15
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Sorry I'm currently cruising so I'm a bit slow. My vent has a screen but no filter. Since I have no stirrer, I line my container with a contractor bag Sooooooo no cleaning is required.

On the separation off urine. I have used "hassocks" toilets where it all goes in together and the smell starts within a day. But even worse, emptying it is a mess if that bag gets a hole in it! Now I've not tried it all of course, but I believe it would take lots of organic matter to absorb urine from 5 people!

It's my opinion and experience that if you want any time between empties you must separate.

On the fan, they are cheap and easy to get and I believe all the commercial ones use them. I can only hope it lasts, but yeah it's easy to replace if I need to.

As an ironic side note I had odor start about 5 days into this trip. Of course I unwisely quizzed my crew about who was getting urine into the compost. Then when I went to empty it I realized the smell was from a very small leak in the urine plumbing. boy did I feel dumb
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