Venting Yurt waste lines

[Sproutnik]

I live in central NC. I am building a yurt on my farm (w/ 3" septic) and I am having trouble figuring out the waste venting for my fixtures. Our yurt is a round, soft-walled structure where the exterior, weather-facing layer is a type of extremely durable vinyl composite fabric. I cannot cut through the roof or the sidewall for plumbing vents.

My yurt is built on top of a fairly tall platform, where there's approximately 3 feet between the bottom of the joists and the soil level.

For the 2 sinks (and possibly the washing machine standpipe), I was planning on using AAV's on each fixture. My standpipe interior opening will be much lower than standard (perhaps 18" off the finished floor!) due to a weird european-style all-in-one washing machine/dryer that doesn't dry properly unless its installed on a pedestal or has a non-standard standpipe height.

I've included a few very bad drawings to show the setup and my guess at how to plumb it. Please excuse my terrible drawing ability. As you can see, I am at a loss for how to vent the shower stall and toilet/WC. The island/chicago-style drain loop would be ideal but is not allowed for anything but sinks, but then again, the whole project falls under the extremely lax farm rules.

Any help y'all can provide would be appreciated -- my very pregnant wife is getting punchy!

EDIT: The distance from the most remote fixture to the septic inlet is less than 10 feet. It's a 30' diameter yurt so all of this plumbing is in a very small space.

 

[Sproutnik]

I realized that I didn't directly ask a question (and I suspect my hastily drawn diagram that is replete with errors makes folks feel giving me advice is a gargantuan task that involves me first getting a clue, sorry!). Based on the info I provided, how can I vent my shower and toilet without cutting a hole through the roof or exterior wall of my yurt?

 

[Sponsor]

 

[Reach4]

I think your system works as drawn in drawing3, except that your AAV for the standpipe serves no purpose. Your drain elbows should all be long sweeps properly oriented. If your layout is not fixed, it is normally best to have the toilet as the last thing downstream. I did not take much from drawing2.

There are various things that will not meet US code, such as the standpipe p-trap below the floor. But I think you are looking at function. Keep the height of the standpipe above the trap at 42 inches or lower.

I am not a plumber.

 

[Sproutnik]

it is normally best to have the toilet as the last thing downstream

This best practice is in reference to the toilet drain inlet being the last thing downstream, correct? (I.e., not the location of the toilet vent). It appears that I could run the toilet drain directly to the septic inlet and stack the other waste lines on top of it without changing the layout of the fixtures, yes?

your AAV for the standpipe serves no purpose

Thanks for catching that. The vent for the standpipe should be located after and above the standpipe trap, correct? I might be able to fit the standpipe trap inside the yurt, in which case I can install a vertical vent capped with an AAV above where the standpipe trap ties into the drain pipe.

What happens if the standpipe length above the trap is too short? Is 18" long enough? Is there a risk of spilling over the top of the standpipe when the washer is actively pumping water out at a high rate of flow with a short standpipe?

 

[Reach4]

This best practice is in reference to the toilet drain inlet being the last thing downstream, correct?

I would call that the toilet drain connection rather than inlet, but yes.

Thanks for catching that. The vent for the standpipe should be located after and above the standpipe trap, correct? I might be able to fit the standpipe trap inside the yurt, in which case I can install a vertical vent capped with an AAV above where the standpipe trap ties into the drain pipe.

In that case, you would not need the separate real vent for the standpipe I think.

What happens if the standpipe length above the trap is too short? Is 18" long enough? Is there a risk of spilling over the top of the standpipe when the washer is actively pumping water out at a high rate of flow with a short standpipe?

Codes usually specify a 18 inch minimum, and the max varies with the code. I think IPC allows 42, but UPC allows only 30. Canada allows the p-trap to be below the floor, but US codes say above.

The worry about too long is the fear that the water will develop such momentum, that the water keeps going and empties the trap of water. In practice I think this is less of a problem than it might seem, since the washer ends up dribbling water at the end of its cycle, rather than ending up with a high flow.

 

[hj]

You CANNOT connect the washer, toilet and standpipe vents together UNTIL they have EACH risen at least 42" above the floor.
Using an AAV REQUIRES that there be at least one vent "through the roof", and it should be at the farthest point upstream from where the sewer enters the building.

 

[Sproutnik]

You CANNOT connect the washer, toilet and standpipe vents together UNTIL they have EACH risen at least 42" above the floor.

Since I cannot go through the roof or the wall of my yurt, are you saying that I'd need to run individual vent pipes from the washer, toilet, and standpipe vents horizontally (well, really, diagonally for appropriate slope) out under the joists, where they would then bend, and run up along the exterior wall to a height that is 42" above the interior floor, at which point I could connect them?

If that's the case, that's a heck of a lot of vertical exterior piping. This is why I initially wanted to create a large loop vent that would serve the fixtures, so I could use a connected foot vent to run out from under the yurt to a vertical exterior vent running up the outside of the wall. Except those aren't allowed for anything except kitchen sinks and lavs (at least, haven't been allowed for many many years, though I don't know what was discovered that changed from much more permissive use in 1960's code to where we are today).

Using an AAV REQUIRES that there be at least one vent "through the roof", and it should be at the farthest point upstream from where the sewer enters the building.

This requirement of one vent to outside is why I'm puzzling over my venting rather than rolling the dice and using AAV's for everything (which having lurked here for a while, I'm aware that the AAV's will fail and when they do, the septic gas released risks killing everyone in the very breathable yurt, if not within a 5 mile radius).

Frustrated jesting aside, I do want to take care to be as code compliant as I can without damaging the integrity of my roof or wall fabric.

 

[Reach4]

This requirement of one vent to outside is why I'm puzzling over my venting rather than rolling the dice and using AAV's for everything (which having lurked here for a while, I'm aware that the AAV's will fail and when they do, the septic gas released risks killing everyone in the very breathable yurt, if not within a 5 mile radius

AVCs will admit air, but they will not relieve pressure. Imagine gasses bubbling from the septic tank or even action within the drain. Imagine a dose of water pushed by a toilet, and the air in the drain pipe fighting back with air pressure. Imagine a low pressure front comes through the area.

NC appears to base their code on the IPC.

 

[Sproutnik]

Imagine gasses bubbling from the septic tank or even action within the drain. Imagine a dose of water pushed by a toilet, and the air in the drain pipe fighting back with air pressure. Imagine a low pressure front comes through the area.

Thanks for the gross imagery, point taken! I'll have a vent to open air, I just don't know how to interpret hj's comment regarding no vent connections until 42" above floor level. There's got to be a way to vent this without cutting a hole in my fabric wall, which will cause all sorts of other issues.