I've got a question about utilizing a wet vent.

I've included two drawings with this post to illustrate my question. This is all contained in my kitchen ceiling. Above the kitchen is a bathtub and a clothes washer.

The first drawing is approximately the setup I just demolished. The washer and tub drained to a 4-way fitting which sat in a "flat" orientation (at a 22° angle in the vent direction). Simple enough, but I think it was done this way because the washer/dryer was a retrofit and this avoided opening the wall by containing all the work in the joist bay.

Well, all the walls are open now and I'm demoing the iron pipe and reframing some of the ceiling.

What I'd like to do is drawing #2. Basically, run the washer drain straight into the drain it's going to run in to anyway (with a slight jog), and make the drain line from the tub a wet vent to make use of the existing vent line.

My understanding of wet vents is they're allowed as long as the line doesn't drop more than its own diameter. In this case, I'll use a 2" line, and it drops only ¾" to an inch between the wall and the vent.

Actually, now that I've put this on paper it looks a whole lot more simple than when I was planning this in the workspace. Do any of you have a problem with this before I show it to my code inspector?

 

"My understanding of wet vents is they're allowed as long as the line doesn't drop more than its own diameter."

Are you sure you're not using the provision that pertains to trap arms? That causes a s-trap if you drop more then the dia. of the pipe even with a vent.

The wash machine line needs to have a trap and vent.

The vent comming off the tub hook-up needs to have a combine (not a tee) rolled up on a 45deg. angle where you're tying in the vent (under the UPC thats called a flat vent), when you get into the wall you will have to add a clean out, then reduce down to 1 1/2 and continue your vent.

This may not apply if you are using a different code.

 

I'm not familiar with a "combine." Does it go by another name?

You say I'll need a cleanout in the wall. I assume you're talking the drain line, and not where the vent goes vertical in the wall behind the tub? Can you explain that one? Is it due to the laundry? Is this something I'd install after the trap in the laundry line, above the floor upstairs?

I'll have to double check what I thought I read in my plumbing book re: wet vents.

 

A combine is one fitting that (COMBINES a wye and 1/8 bend), you can make your own by gluing the two fittings together.

I'm talking about the vent line, under the UPC a flat vent has to be run like a drain line because of no wash down on the vent connection; the c.o. is required because of the vents connection prone to get blocked. They are easy to run, just run your line 2in. up in the wall about a foot or so with a plugged fitting close to the edge of the wall, then you can reduce your pipe to 1 1/2 and tie into your vent, they make chrome plates to cover it when you're done.

 

You can't wet vent a washing machine under the UPC, and a question has already been raised about your flat vent. Can't tell for sure in your drawing.

 

Thanks. I found that tidbit about no washers on wet vents, and also discovered the error in my thinking.

The previous guy improperly installed the trap in the joists (I left that out of my drawing to keep it clean), but now I understand why he did it: installing the trap above the floor would have resulted in a broken vent.

I've got a new plan but will have to find a way to cram a 2" trap & drain into a 10" stud bay.

Are tubs 1-1/2" traps, not 2", to meter the flow of water from a full tub?

 

Ok, I've rejiggered some things in my head. This look kosher?

The laundry stack, trap & laundry drain/vent has to fit in a 10" space (bordered by the dedicated vent stack on to the right), but I can do that with copper.

That means my laundry drain and tub vent are only going to be ~12" apart where they connect. Is that anything I need to worry about?

I assume this arrangement does away with the "flat vent" requirement and no longer warrants a vent line cleanout?

 

>>>That means my laundry drain and tub vent are only going to be ~12" apart where they connect. Is that anything I need to worry about?>>I assume this arrangement does away with the "flat vent" requirement and no longer warrants a vent line cleanout?

 

Thanks, you've been an invaluable help.

Two questions:

(1) with respect to cleanouts, how far from or how high from the associated connection can they be? For instance, what prevents me from using the vent outlet on the roof from being a cleanout? Or placing it in the attic? It's not that big a deal to me as it will be hidden behind the washer; just curious.

(2) any insight to the 1-1/2" trap requirement on tubs vs. 2" on showers?

 

You want the clean-out somewhere near the line you want to clean. That c.o. is for the purpose of cleaning the vent connection between it and the tub line because that type of vent is prone to becoming blocked, putting it somewhere else would make it useless.

A tub has a large container to hold water so a 1 1/2 drain will work fine. With a shower the pan is limited to how much it will hold so you need a larger drain to keep it from flooding the floor. Beer 4U2

 

Ok, one last question with respect to what you wrote about the vent wye being "rolled up" on a 45°, what I assumed you meant with the wye's branch arm kicked up half way between flat and vertical.



Can a wye go in vertically oriented, as I've drawn below, with a 45° elbow oriented in-line to put it back at horizontal, then a 90° elbow to change directions?

Is this only required for the vent wye so it can breathe, versus the drain line wye which can run in flat (wye + 45°)?

 

It's prefered that all take offs are run at a 45deg angle, that limits the snag point when they are run flat, you can run the rest of the line the way you have it drawn except use a long turn ell where you show a 1/4 bend.