CountryPlans Forum

Hey guys, got one more question on my mind... Code calls for a 3'' vent due to frost closure, but I'm wondering if I can get away with this setup in a cabin:

(https://img.photobucket.com/albums/v667/AirsoftAndy/wcabindwv.jpg)

Obviously very simplified.. Every fixture besides the kitchen sink is close enough to the stack for venting. The sink will get a studor vent. The reason I want to use a 2'' vent is because space is very limited (down to the last inch), and I would rather run the vent through a 2x4 interior wall than beef it up to 2x6. Think this would work? We aren't trying to be code-compliant, just functional.

By looking at the drawing you'll be sucking the water out of the shower p-trap every time you flush the toilet. Every fixture should have it's own vent starting at the point where the trap connects to the system. These vents can be connected together into a single vent. For what you are showing I'd recommend atleast 2- 2" vents. 1 might work but it's no where near code.

The toilet is only about 4 1/2' from the 2'' vent, and the shower about 2'. Isn't that close enough for the two of them? If not, how about running a separate 2'' vent for the shower, and joining the two vents into a single 3'' in the attic?

Thanks for the drawing, I'm understanding about the shower problem now, but it's really not possible to put a vent behind the toilet. how about this setup?

(https://img.photobucket.com/albums/v667/AirsoftAndy/wcabindwv2.jpg)

Like I said, every fixture is within the critical distance to the main vent except the sink, which would be much easier to put a studor on than revent..

   Maybe this site is of help . . .


http://www.hometips.com/how-it-works/plumbing-drain-waste-vents.html (http://www.hometips.com/how-it-works/plumbing-drain-waste-vents.html)


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Maybe I'm just dense, but I thought that if the fixtures were close enough to the main vent, they didn't need a separate revent of their own. Doesn't the stack just become a wet vent for all the fixtures in the last image I posted?

In some cases you can vent several things off a common stack. You've got to use the right fittings and the stack must be full size 3" through all the connections.

So, is the danger that too many fixtures could be drain at once, and then they'd interfere? The shower or washer could have a revent easily enough, but it seems that the toilet would probably be the biggest potential problem.

The venting issues aside, the 2" run to near the roof then a 3" through the roof is acceptable, at least it was to my inspector.  There is a minimum the 3" has to run inside, 1-2' if I remember right.  Your main vent also needs to be the same size as the main drain out of the house... ie if you have a 3" run to sewer/septic you need a 3" out the roof, at least that's my understanding.

Good luck, the DWV was the most frustrating part of my whole build.

Each fixture needs to be vented individually as Scott mentioned.  The toilet can get away with a 2" tied into the 3 as long as other fixtures provide the rest of the venting to match the size going out.  You can put a vent right after the toilet fitting and place it at a 45 on the top quarter of the pipe then over to the side to get it out if in close quarters.  Of course I don't know all of the problems you are dealing with.

Wet venting is generally extremely limited and I always find a way around it just so I don't have to argue with an inspector about it.

Scott knows much more than me about this as it is his job, so if I said something in conflict with what he said, believe him.... [waiting]

One unvented fixture especially a toilet can suck anothers trap dry as the water goes by it's drain and wants air to follow it.  If that fixture is unvented then the only place for air to come from is by pulling it through the trap.  Then you will get to sit around sniffing sewer gas until you refill the trap.  This can be deadly especially if the entire family has dined on tacos and refried beans in the recent past.  d*

Actually the septic system makes methane and other gasses on it's own as it digests the wastes.

Thanks for the info.. Though, I'm not really understanding how any traps could get sucked dry in the second sketch I posted, as every drain goes directly into the 3'' stack, so air should be freely available (unless everything's draining at once, but it takes an awful lot of water to completely fill a 3'' pipe). I read somewhere that a 3'' wet vent can support up to 12 d.f.u., and we're well under that.

If it's possible to give the toilet a closer vent of its own I'll seriously consider it.. The dwv has always confused me and I'd rather be safe than sorry, but we could save a whole bunch of pipe and time by wet venting and I haven't read anything in a plumbing book that discouraged it yet (as far as I can tell...).

In reality it will probably have no problem, but in the technicalities of the code, the waste water should all go down and have a vent available to each fixture above it's drain without the waste water of another fixture running through it.

In the last one you posted the toilet seems like it has a long arm to it before getting to the 3 inch.  It may try t suck the bowl dry before venting if that is the case.  Schematics are not always totally representative of the actual conditions though.

Sometimes all that happens is a nuisance. I did a toilet once and cheated on the vent. It gurgled every time it was flushed.

Quote from: glenn kangiser on November 13, 2009, 12:33:52 AM
In the last one you posted the toilet seems like it has a long arm to it before getting to the 3 inch.  It may try t suck the bowl dry before venting if that is the case.

It's actually only about 3' from the downward bend (I imagine it would be a double wye), and about 4' from the vertical stack. It wouldn't be the end of the world if it gurgled, but we obviously don't want a house full of methane. ;)

 The toilet trap will stop the methane if it doesn't get sucked dry.