Humanure Bucket with Urine Diversion

Hi,
I'm building a cabin with a humanure bucket toilet. I like diverting urine to keep the bucket dry. I don't want to capture the urine separately because emptying it manually would be too frequent for my liking. So I had a plumber rough-in a line for the urine to flow towards the septic field. No water, just gravity and urine. My jurisdiction requires septic field. My plumber warned me that a line directly between the septic system and the toilet would stink up the house without a P-trap. But if we installed a P-trap it would sit full of pee and that would also have a stench.

Should I put a valve on the urine line so that a user opens it before they sit down and closes it after? Maybe a lid over the urine cup would be easier? There must be a better way. Maybe use a P-trap and chase it with a cup of water? I want to be water conscious because we'll have rain collection only.

The HRV unit will be getting rid of bathroom air constantly, so that's a mitigating factor.

Do you realise urine mixed with water is good for the garden.
If you explained where you live locals may be able to share knowledge.

I put a P-trap on our urine diverter in one our toilets. We have to flush it occasionally with with water and/or vinegar. The exhaust fan also helps with the smell. If you have a cold water line running to your toilet area I think a really snazzy solution would be running a drip line with a timer to the urine diverter bowl.

Our second compost toilet doesn't have a P-trap and we haven't had any issues with smell. However, it runs to a gray water system rather than the septic tank. I also did a better job sealing it and it has a bigger exhaust duct (2 inch pipe) then the first toilet.

P-Traps are fairly easy to add. I think I would build a really well air sealed toilet compartment with a good venting and see it goes before adding a P-trap.  

Nick Neufeld wrote:
The HRV unit will be getting rid of bathroom air constantly, so that's a mitigating factor.

I would be wary of a constantly running HRV. Our bathroom exhaust fan overpowers our toilet exhaust fan so it pulls air from the toilet compartment while it's running so it only goes when we're showering.  

John C Daley wrote:Do you realise urine mixed with water is good for the garden.
If you explained where you live locals may be able to share knowledge.

I'm on the Canadian prairies.
Very cold winters.

We use a similar toilet setup in our outhouse, except in that one the urine goes to a 4L jug and then to our plants.

I'm ok with letting the liquid gold go from the cabin to the septic field. I can harvest the extra grass growth from that field if I'm looking for a nitrogen boost somewhere else.

Aaron Yarbrough wrote:I put a P-trap on our urine diverter in one our toilets. We have to flush it occasionally with with water and/or vinegar. The exhaust fan also helps with the smell. If you have a cold water line running to your toilet area I think a really snazzy solution would be running a drip line with a timer to the urine diverter bowl.

Our second compost toilet doesn't have a P-trap and we haven't had any issues with smell. However, it runs to a gray water system rather than the septic tank. I also did a better job sealing it and it has a bigger exhaust duct (2 inch pipe) then the first toilet.

P-Traps are fairly easy to add. I think I would build a really well air sealed toilet compartment with a good venting and see it goes before adding a P-trap.  

Thanks for sharing. Very helpful.

I was planning on having bathroom venting without additional venting for the toilet box. I'll rethink that decision.

Hey Nick,

I just overhauled our bucket toilet. Here is a video I made about it:


And my blog article about it:
Building a Better Bucket Toilet

In short, I rebuilt the toilet compartment to make it tighter, added some air sealing measures to to the lid and seat, removed the P-trap and increased the exhaust duct size from 1" to 2".

Lol...pee-trap!

Christopher Weeks wrote:Lol...pee-trap!

I know. The irony.

We free range our pee now.

Presumably there is some kind of hand washing station near this system.  It would be neat to use the waste water from washing hands in that sink to automatically chase the waste of the urine diverter, and thus fill the p-trap to prevent venting odors.  Users' normal pattern of washing hands provides a stacked function without extra thought involved.

You'll have quite a bit of grey water from running cold water while waiting for hot, from showers, from rinsing dishes, from washing/rinsing clothes that you could chase it down through the line with that water.  You'll want to keep that whole diverter clean anyway.   Store the grey water in milk jugs in the bathtub/shower.  No point in using power to deal with a situation like that when all you need is a manual "flush".

You said you didn't want to dump a pee bucket because it would be too frequent, but I question that. Here's our system: We have five buckets in an outhouse a short distance from the house. It doesn't smell because little pee goes in there, and we dump a handful of sawdust on top of each deposit. When all the buckets are full I take them to the poo bins a farther walk away; one side is filling each year, and in the spring I empty the other side which has been untouched for a full year. It's compost by then but I use it up in my orchard and sometimes I have some left for the flowerbed. Meanwhile, in the house we have what I call the pisseria, similar to the wooden box around a platform constructed to fit a five gallon bucket that we have in the outhouse. This does stink but the lid contains it (an ordinary toilet seat built into the box). I have to dump this bucket maybe twice a week (two person household). Most of the phosphorous and nitrogen we pass is in the urine, so it should not be wasted. But I tried a couple times using it diluted in water on plants and didn't like the results, so I dump it on compost piles; I have one by each of three gardens and a flowerbed, and I have several piles in the woods around our clearing, of fallen branches, rotting logs. etc.

It seems like you could install a pee-trap for the pee and fill it with some magic blue trap sealant. This stuff is used in waterless urinals to reduce the urine smell and prevent anything from the septic tank / sewer from coming back into the room. It's lighter than urine so it will create a floating barrier on top of the fluid in the trap. Urine will pass through it. You will probably want to flush it out with a bucket of water from time to time and add a fresh supply. Here's a link to get you started down this drain, oops, I mean rabbit hole

https://www.waterless.com/blog/getting-to-know-blueseal

Or, you can search for 'waterless urinal fluid' to find out where to buy some. Amazon also has the waterless urinal cartridges which would work instead of a trap if you could figure out a way to plumb it in (maybe a Fernco flexible coupling onto a large pipe with a reducer?).