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"Ventless" Plumbing System

pinko's picture

Umm, yea, I have a customer who has built an addition (metal building on slab) and is finishing the interior. The "plumber" has roughed in everything to stub-outs (drains only). I'm there to finish the interior. Arrive today for a pre-job walk-through and notice the drain stacks to the individual fixtures (namely, the vanity, toilet, kit sink, and laundry tub) have no vents. The stubs are just capped PVC about 3 feet from the slab. I ask where's the vent stack? Customer says the plumber told him it was a "ventless" system.


Now, I realize he's been hosed, but what advice do I give on remedying the problem? I was ready to set the shower unit tomorrow, but...if the drain is not vented (every thing's creted in now, of course), any fix would likely require the floor under the shower to be broken out so the plumbing can be redone... Correct? Any chance I've been living under a rock for sometime and there's some new "ventless plumbing system"---and I'll look stupid for telling him his plumber screwed him? And is there a fix that won't require the slab to be torn up?

For the record, I once built a small (600sf) house and vented all plumbing fixtures (1.5 baths and kitchen) through a single 1-1/2" vent leg on the upstairs bathroom.. Totally wrong, but the system 'worked' fine.

But I don't want to experiment with any half-baked remedies with my customer... The kit sink, vanity and laundry can still be properly vented--up and out--but what of the toilet and shower?

(post #105008, reply #1 of 14)

I use these -

Forrest - not a plumber

(post #105008, reply #2 of 14)

Air admitance valves can be used in cases.

But they can't be the only vent, but that might be provided rest of the house.

Also don't know if one can be installed close enough to handle shower and toilet.

Also some local codes don't allow them.

A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.

Edited 10/22/2007 6:33 pm by BillHartmann

. William the Geezer, the sequel to Billy the Kid - Shoe

(post #105008, reply #3 of 14)

Yea, I'm aware of the AAVs (I've used them before, and I like them).

But, no, there is no other vent...this is a detached addition (20' from the main house) and it ties directly into the house septic tank on it's own 4" pipe at a wye near the tank inlet.

Shower drain is first in line from the main sewer, then toilet, then vanity, then kit sink, all on about a 12' run. First place I could put an AAV is on the vanity, so yea, it would be wet-venting the toilet and shower as well. If I got the 'Maxi-vent' (thanks Forrest), think it could handle everything?

And what's the consensus on this plumber? Hack or not?

(post #105008, reply #4 of 14)

Hack or not?

What does code call for in your area?  I think it was already stated that you can't do all AAVs, but need at least 1 vent through the roof (it does where I'm at). 

Edited 10/22/2007 7:19 pm ET by john7g

(post #105008, reply #5 of 14)

Sounds like the plumber was trying to avoid putting the vent through the metal roof, it's not as easy as a shingle roof but it can be done.

If you go with AAV there should be access to them if they should need changed.

(post #105008, reply #7 of 14)

I've put metal roofs on all my houses. I've always used a simple rubber and lead collared roof jack for the vent penetrations (Oatey has 'em at Lowes)..not a big deal. But, THIS roof is about 36' up. You're probably right that the plumber avoided the trek up there...And so will I.

Agreed that the AAVs need to be accessible. Thanks for the info. I personally think this plumber ripped the customer..I hate to be the one to mickey-mouse a fix for another's over-charged incompetence, though.. And I have to wonder what else is screwed up underneath that slab..I'm leery of mixing my labor w/ someone else's flawed project.

(post #105008, reply #6 of 14)

As long as their is a stack somewhere in the system you can use studer valves on the addition. My plumber does it all the time.

Its a pretty good savings in labor and materials.


Family.....They're always there when they need you.

(post #105008, reply #8 of 14)

I'm guessing there was no permit pulled for this project.

I have installed AAV's & I don't like them, but they do work in certain circumstances.

Like others have stated you need to have a vent exiting the building.

Like their name implies AAV's let air in, but do not let air out, creating a pressure to the system which can cause some traps to bubble sewer gas.

“The Hand of providence has been so conspicuous in all this, that he must be worse than an infidel that lacks faith, and more than wicked, that has not gratitude enough to acknowledge his obligations.”George Washington


(post #105008, reply #9 of 14)

>>I'm guessing there was no permit pulled for this project.

No doubt.

And it was a "redneck plumber" who did the work (customer's words).

But did he get hacked? Methinks so.

Is this a tragedy, though? Can I install the shower and not worry about it having to be later removed for a plumbing re-do? That's my only pertinent concern right now.

(post #105008, reply #10 of 14)

Where do you fit in in this equation?


(post #105008, reply #11 of 14)


You mean what was I tasked to do? Not rough-in plumbing. Customer did not know he had a problem until I pointed it out to him. I'm not even sure he cares to fix it. But I'd like him to be informed anyhow.

(post #105008, reply #12 of 14)

So what are you "tasked" to do?


(post #105008, reply #13 of 14)

Matt, like I said, I'm doing the finishing inside...sheetrock, finish-wiring, trim, cabinets, etc.. I need to set the shower base and connect the drain first, so the vent issue is a concern. And I obviously don't want to close up the walls until the plumbing is satisfactory. At this point, it probably won't ever be to code, but it needs to be functioning. That's the goal here.

(post #105008, reply #14 of 14)

If you are working on a system with no permits, no inspection, who do you think will be scrxwed when there is a prob. with the system?, major voodoo!.


"If all else fails, read the directions"