Questions About Composting Toilets

Nov 4, 2018
155
Hunter 28.5 Catawba Island, OH
I've been doing some research on composting toilets. However, the re-fit of my head is a couple of years away (The laminate used by Hunter is chipping and flaking.).

As a Great Lakes sailor, I like the idea of a compositing toilet. No more limitation of my holding tank. No more trips to the gas dock for pump outs, and of course, the $5.00 every time I pump out. My Hunter 28.5 has the holding tank - and for that matter the water tank - molded into the floor pan of the boat. I would plan to re-purpose the holding into storage space. After a good through cleaning and sanitizing, thick lots of Clorox.

But, some questions:

- I've several videos about people who have installed composting toilets. The people claim any where from a monthly clean out to a six month clean out. All of these people appear to be live aboards. I live as much as I can on my boat during the sailing season here on Lake Erie. That means a maximum time of six months. Realistically, what can I expect?

- Venting: the videos show what appears to be three inch venting hose. Is that large of a hose really necessary? Could I use my existing one inch thru hull vent?
 
Apr 22, 2011
743
Hunter 27 Pecan Grove, Oriental, NC
I installed a C-Head in my H-27. The manufacturer recommended that the head not to be vented unless there is a build up of moisture in the composting bowl. They did include a vent hose and connections if venting became necessary. I believe the vent hose is 1 1/4". Too early to tell if I will need to vent. I know that Natures Head and Air Head do come with venting. Not sure of the size.
 
Dec 2, 1997
8,168
- - LIttle Rock
An occasional "weekend warrior" might be able to wait six months to empty a compostet, but most live-aboard couples have to empty a composter about every 3-5 WEEKS.

An alternative to a composter that's very popular with owners of boats <30': an "MSD" portapotty.
The "MSD" designation in the model name/number means it has fittings for a pumpout line and vent line, and is designed to be permanently installed (actually just sturdier brackets than portables, so you could still take it off the boat if you absolutely have to), which means that although it's still called a PORTApotty, you don't have to carry anything off the boat to empty it.

A 5-6 gallon model holds 50-60 flushes...you'd need at least a 30 gal tank to hold that many from a manual marine toilet. No plumbing needed except a vent line and pumpout hose--so no new holes in the boat...and -0- maintenance needed except for rinsing out the tank--which you can do with a bucket while it's being pumped out. Total cost including the pumpout hose and vent line is about $200--a fraction of what you'd spend for toilet, tank and all the related plumbing needed. And the best part is, you have all the advantages of a toilet and holding tank without giving up a single square foot of storage space.

Check out the Dometic/SeaLand 975 MSD Sanipottie...available from a number of retailers including the sbo.com online store here.

--Peggie
 
Jan 19, 2010
10,185
Hobie 16 & Rhodes 22 Skeeter Charleston
Check out the Dometic/SeaLand 975 MSD Sanipottie...available from a number of retailers including the sbo.com online store here.

--Peggie
I have a domestic MSD on my boat.It is not plumbed for pump out at the moment but I’ve thought about it ... Peggie must have a very different digestive system from me. #1 goes over the side but there is no way mine will hold Anything close to 60 flushes :poop::yikes:
 
Dec 2, 1997
8,168
- - LIttle Rock
Dometic/SeaLand portapotties are available in 2 sizes--2.5 gal and 5 gal. Sounds like yours may be the smaller one. Easy to tell...the 5 gal version is 15.25" tall including lid.

Also...if yours doesn't have the vent and pumpout fittings, it's not the MSD version.

--Peggie
 
Jan 19, 2010
10,185
Hobie 16 & Rhodes 22 Skeeter Charleston
Dometic/SeaLand portapotties are available in 2 sizes--2.5 gal and 5 gal. Sounds like yours may be the smaller one. Easy to tell...the 5 gal version is 15.25" tall including lid.

Also...if yours doesn't have the vent and pumpout fittings, it's not the MSD version.

--Peggie
Thanks Peggie

I do have the fittings. I've just never been at a marina with pump out services before so I had no need to plumb it. But I'm reconsidering now that I've moved to Charleston. I did have to replace the ball (check) valve in the flush pump on mine. Easy fix with the kit. Other than that, it works very well.
 
Nov 8, 2007
1,403
Hunter 27_75-84 Sandusky Harbor Marina, Ohio
This is our 21st season with our MSD toilet. I'm with Peggy. I outperforms the holding tank systems on the 15+ charters we have taken in every way. Mostly, a flush is not needed, by the way.

While not "free," pump-out is included in our home marina fees, and in the fees of most of the marinas we visit.
 
Jul 5, 2005
212
Beneteau 361 Sandusky Harbor Marina
I have a Nature's Head on my boat, and I'm a weekender only. I am my wife can go at least 3 months. Usually we empty once during the season, and by the time the season is over (beginning of October for me) it's time for the second emptying.
 
Dec 2, 1997
8,168
- - LIttle Rock
dgranger...depending on the age (plastics get dry and prone to cracking with age) and size of your existing pottie, you might consider "upgrading" to a new 5 gallon. You could just replace the tank with the larger one, but that would cost you about 90% of the price of a whole new one so not worth doing...and besides, the new one is not only better looking but also has a built in tank level indicator to let you know when it's time to pump out.

--Peggie
 
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Jul 1, 2010
873
Seaward 25, Catalina 350 Erie, Pa
I can't speak for the other 2 brands, but we installed a C-head on our trailerable boat (Seaward 25). We usually go a week or a bit longer before we dump the main compartment with 2 of us on board. We did vent it because I just assumed I should. The unit comes with about a 1 1/2 ish vent hose. I attached a pvc tube to our pumpout fitting and t'd the vent into that. On the top side of the pumpout fitting I attached a pvc "t" . This allows the breeze to blow through and pull on the vent. No inline fan needed. C-head used to include a vented 5 gallon bucket lid with the c-head (not sure if they still do) that you could vent in series with the head. So when the head needs to be dumped, I dump it in the 5 gal vented storage container. I can get at least 3 dumps of the C-head into that. With the c-head going another week, we could easily get a month's worth of use out of it before having to find somewhere to dump it. On our boat, I just take it home and bury it.

We also take the c-head to our off-grid cabin (am there now) and it's great for that use too. We don't vent it at the cabin and have never felt the need to.
 
Aug 9, 2020
17
None yet None yet SF Bay
I',m curious about the odor of the MSD type toilets. I am looking at trailer sailboats and don't know how well these heads control odor.
 
Dec 2, 1997
8,168
- - LIttle Rock
As well or better than traditional toilet and holding tank systems. The tanks are sealed except for the vent, so there's no odor from the tank via the bowl...and odor out the vent can be prevented with any holding tank product that actually works. in any other holding tank. The vent line and pumpout hose are the only hoses and they're short. However it is important to buy the best odor permeation resistant hoses, same as you would use in a traditional system. I'm pretty sure that if you ask people here who have MSD portapotties to rate them, their answers will be 100% positive.

--Peggie
 
Feb 8, 2014
1,300
Columbia 36 Muskegon
I've been doing some research on composting toilets. However, the re-fit of my head is a couple of years away (The laminate used by Hunter is chipping and flaking.).

As a Great Lakes sailor, I like the idea of a compositing toilet. No more limitation of my holding tank. No more trips to the gas dock for pump outs, and of course, the $5.00 every time I pump out. My Hunter 28.5 has the holding tank - and for that matter the water tank - molded into the floor pan of the boat. I would plan to re-purpose the holding into storage space. After a good through cleaning and sanitizing, thick lots of Clorox.

But, some questions:

- I've several videos about people who have installed composting toilets. The people claim any where from a monthly clean out to a six month clean out. All of these people appear to be live aboards. I live as much as I can on my boat during the sailing season here on Lake Erie. That means a maximum time of six months. Realistically, what can I expect?

- Venting: the videos show what appears to be three inch venting hose. Is that large of a hose really necessary? Could I use my existing one inch thru hull vent?
You're lucky it's only $5.00. Here at the city marina in Muskegon the pump out "broke" about five years ago and they've refused to fix it. The only other two places on the lake charge $15 and $25 and they're miles away. I'm putting in a C-Head this Fall. Best thing with composters is you can legally dump them in any trash can or dumpster. No different than tossing diapers or kitty litter. That makes it so easy it doesn't really matter how long you can go, you just find a trash can and dump whenever you want to. We take the regular trash ashore about once a week, we'll probably dump the head at the same time.
The term composting toilet is really a misnomer unless you are on land and hold the contents for at least a year before putting it on the garden. That's how long composting actually takes, on the boats we are just starting that process.
 

splax

.
Nov 12, 2012
678
Hunter 34 Portsmouth
does the c-head actually compost ? what is involved in emptying the MSD? what advantage to removing the manual toilet and connecting the pumpout to the MSD? I am considering the mod to avoid the holding tank headache...
 
Oct 2, 2008
3,626
Pearson/ 530 Strafford, NH
A cruising friend replaced his forward head with a composter last year. He had to adjust the sole height to get it comfortable. Recently the aft head disintegrated during a pump-out. After a thorough cleaning, he contacted his C-head company and they were able to customize the tank so it would fit in the aft cabin. So important to be able to fit into the space provided. His original head was a vacuum type and really had no issues with that style or engineering, just wanted to change disposal methods.
 
Feb 8, 2014
1,300
Columbia 36 Muskegon
does the c-head actually compost ? what is involved in emptying the MSD? what advantage to removing the manual toilet and connecting the pumpout to the MSD? I am considering the mod to avoid the holding tank headache...
None of the "composting toilets" actually compost. They start the process but don't finish it. As I said above starting with poo and ending with usable compost to put in your garden takes about a year. The folks using them in off-grid homesites do complete the cycle, they dump onto the compost pile with all their other organic garbage. It's very eco-friendly as none of the stuff ends up in landfills, but it just not possible in a boat unless you have access to a real compost pile. Maybe some people do it that way, but I don't know of any.