Composting Toilet Liquids Diversion

[Steve Mason]

We have had a AirHead on our boat for years. When we ordered it from the supplier they fitted a discharge fitting at the base of the liquids container. A hose connects to the outside of the container fitting runs to a small pump and overboard above the waterline via an unused thruhull fitting. Works wonderfully. Imagine it would be easy to retrofit to another setup since the container is plastic and there are lots of options with a hose barb fitting on the exterior.

[Sailorguy]

Retrofitting the liquid tank, adding a pump is what I did. It has worked out very well. In our install the bottom fitting option would have been difficult to route to the OB discharge. Much better option than pouring contents into the head sink or directly overboard.

[CaptJPMcGuire]

Sea Lawyers --a question --
In a NDZ---Can the sea sick crew puke over the side ---legally??

[Stickan]

I used a Natures Head toilet this season and I was cruising in the Baltic sea. The Baltic is brackish and has severe over nutrification problems which causes algae growth and dead bottoms. It is therefore wrong to put the urine into the water. So we emptied the urine container into toilets if we were in marinas and otherwise a discrete place that looked like it needed some extra nutrients. It is recommended to have an extra container if you are several aboard. All in all the system worked fine and we had no problems with odour.

[emilecantin]

Sorry for necroposting, but I came across this thread looking for options to reduce TP usage.

Looking closely at my brand-new, not-installed-yet Airhead, I noticed something relevant for bidet usage. The solids trapdoor, while not sealed by any means, is built in a way that any liquids hitting it when closed will be diverted to the liquids container through a second "level" under the bowl.

This seems to indicate that using a bidet with the trapdoor closed wouldn't add any more liquids to the solids bin, at least on the Airhead. Anyone here tried this?

[Mike OReilly]

Originally Posted by emilecantin

Sorry for necroposting, but I came across this thread looking for options to reduce TP usage.

Looking closely at my brand-new, not-installed-yet Airhead, I noticed something relevant for bidet usage. The solids trapdoor, while not sealed by any means, is built in a way that any liquids hitting it when closed will be diverted to the liquids container through a second "level" under the bowl.

This seems to indicate that using a bidet with the trapdoor closed wouldn't add any more liquids to the solids bin, at least on the Airhead. Anyone here tried this?

You could run a test to confirm this pretty easily.

Nature's Head is the one I have, and while it does have a closable trap door, there's no way it would prevent water from draining in. And once water got into the main bin bowl, it doesn't divert to the urine container.

So maybe Air Head has an advantage in this regard.

[emilecantin]

Originally Posted by Mike OReilly

You could run a test to confirm this pretty easily.

Good idea!

I actually just tried it with a large glass of water (about 600 ml? it's a very large glass), and while some did make it in the solids bin, it's not a lot, I'd estimate about 20ml.

Running another test with just the bowl over the sink, it seems to be pretty sensitive to the "inertia" of the water. A jet going backwards would definitely go in the solids bin, but drips or a jet going in the opposite direction would make it in the liquids jug.

Here is a pic of the underside of the bowl where you can clearly see the "second floor" that catches the liquids that hit the trap: https://photos.app.goo.gl/Qy1b8tcD98KmcY8u6

[emilecantin]

BTW, I'm interested in the subject because we're switching to a composting head this spring after our holding tank leaked last fall (talk about the ultimate ick factor!), and I've had generally poor experiences with marine toilets anyway (including a black-water geyser when opening the pump-out fitting on my previous boat... a spider had made its nest in the vent!).

The main question is, we're a family of 6, including 4 little girls. At home, we go through an impressive amount of toilet paper, so I'm a bit worried it'll fill up the solids too quickly.

We're also planning an extended cruise so we'll be basically living aboard for about a year.

If anyone has experience using these toilets with large-ish families, I'd be very interested. A family of 4 at my marina is making the same switch and actually tested their Airhead this winter at home and reported no issues.

Plan B at the moment would be to build / buy a second one so we get a better people / toilet ratio, but I only have one head aboard the boat; not sure where the second one would even go.

[Mike OReilly]

I have to say that I don't think a single composting head is going to cut it for your needs. My understanding of Air (and Nature's) Head is that they are designed for two, perhaps three adults for full time use. I think a family of six will quickly overwhelm the system. I think two heads will likely be needed.

And I understand your concern over TP usage. It's fine to deposit a small amount of TP into these heads, but it definitely sounds like your situation will produce way too much paper. A little is fine, and may actually help the desiccation process. But too much will great a fibrous bog.

The bidet approach might work. Another, perhaps simpler, solution is to divert the urine paper to a different container. Just put a little sealable bag beside the head. My spouse does this with her urine paper. Works fine.

[mvweebles]

With four kids and two adults on a 38-foot boat, I'm sure you will have all sorts of challenges to work through. My hunch is you will develop a workable routine that will include daily emptying of liquids. Depending on your cruising style and grounds, will probably still be better than a holding tank.

[emilecantin]

Originally Posted by mvweebles

With four kids and two adults on a 38-foot boat, I'm sure you will have all sorts of challenges to work through. My hunch is you will develop a workable routine that will include daily emptying of liquids. Depending on your cruising style and grounds, will probably still be better than a holding tank.

Well we were four kids and two adults in a 31-foot boat until last year, and in a 22-foot boat a few years before that; we know what we're getting into!

And yeah, every interval I see mentioned for emptying, I assume it'll be at least cut in half for my usage. But then, emptying the holding tank needed to be done very often too, so nothing new here.

Even if I end up having to buy a second head, at least it's only "times-two", not "times-six" like so many things!

I really want to give it a good test with only one head, though. There's really no info on this subject (max number of people), the one data point I have is that it does work with 4 (2 kids). If it doesn't work for us, at least we'll know that the upper bound is 5 or 6 people.

[Mike OReilly]

Originally Posted by emilecantin

Well we were four kids and two adults in a 31-foot boat until last year, and in a 22-foot boat a few years before that; we know what we're getting into!

And yeah, every interval I see mentioned for emptying, I assume it'll be at least cut in half for my usage. But then, emptying the holding tank needed to be done very often too, so nothing new here.

Even if I end up having to buy a second head, at least it's only "times-two", not "times-six" like so many things!

I really want to give it a good test with only one head, though. There's really no info on this subject (max number of people), the one data point I have is that it does work with 4 (2 kids). If it doesn't work for us, at least we'll know that the upper bound is 5 or 6 people.

Sounds like you are well prepared for this next adventure Emile. My caution about the number of people using the head is just so you avoid an ugly disappointment.

You're right about the lack info around numbers and usage. The makers are all rather cagey about giving specific numbers. Nature's Head does specify "approximately 60 to 80 uses" for their main bin. Air Head is essentially the same, so I assume these numbers apply as well. Based on user reports, the two units are fundamentally the same.

But "uses" numbers only tell part of the tale. The main function of these heads is not composting (despite the name). It is desiccation. They do begin the composting process, but the main way they work is to dehydrate the feces. Secondarily, they mix the feces with a bedding material, which further helps in the desiccation process. This is why the rate of adding material matters. With more inputs, more frequently, from more people, there just isn't enough time for things to dry out and mix properly.

I know from personal experience that our head can manage larger numbers for a short time -- a week or two for four adults, full time, for example. But the head becomes less of a composter, and more like a holding tank. It's not functioning as it was intended at that point, so the only thing you can do is empty it frequently.

I'm not trying to dissuade you at all. I just don't want you to be acting on false expectations. Certainly you can give the single head a try, and see how it goes. I'd love to hear the results. But I really think that if you are planning to be full-time cruising with your family, that you will be happier with two of these heads.

[emilecantin]

Okay, so I've given it some more thought, and I think I'd have a better plan B for large crews using these heads. It's a bit more ongoing work, but it avoids the need to buy a complete second head (and where to put it on the boat, which my main concern!)

The idea is to only get a second solids bin, along with a lid that can ventilate (Airhead sells this: https://airheadtoilet.com/product/venting-lid/). You then swap these bins every 3-4 days (TBD), so you have one that's in "active" use and the other is "resting", giving it time to do its thing.

Even getting a 2nd fan / vent etc, this only comes up to less than half the cost of a full 2nd head. I'm hoping I could just tee into the one I'm already installing for the head, though.

Any thoughts on this?

[Mike OReilly]

I hear you about the space issue. There's no way I could squeeze a second one on my 37-footer without doing major renovations.

Your plan certainly gives you a better chance to make it work. Active venting on the resting bin would really help. I think I'd find a way to rig a second fan, and not just tee it off the existing one. But anything is better than nothing. If you can give the rest bin a churn every day, that too would move things along.

You're definitely pushing the boundaries of how these heads were designed to be used. I can't say it will work, but your plan sounds reasonable to me.

[toms-gonesailin]

Originally Posted by Sailorguy

Retrofitting the liquid tank, adding a pump is what I did. It has worked out very well. In our install the bottom fitting option would have been difficult to route to the OB discharge. Much better option than pouring contents into the head sink or directly overboard.

Looking at doing something similar. Wondering what kind of pump and hose you went with in the end? Did you add an anti-siphon valve?

Emptying the liquids tank while offshore in rough seas sucks. And yes even at anchor we empty our liquids overboard. I guess an alternative would be to have a bladder or holding tank for liquids only and then dump that offshore when possible.

Our biggest reason for switching to a composting head was to free our selves from the tyranny of pump outs. With our old marine head we went 2-3 days before our holding tank was full and we either had to go offshore or find a pump out which are sometimes few and far between.