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ameleus 09-19-2008 09:37 PM

pre-stubbed basement bath vent needed? photograph attached shows my stubbed basement bathroom. I'm confused about one of the stubs that is shown between the supporting wall studs. On the photograph I have it labeled as "sink drain" viewing the photograph and my attached plumbing diagram for the basement level and main level, is there a need to vent this basement bathroom? I would assume that the stub in question serves as both a vent and a drain for the bathroom's vanity?

If it is a must, do I have to take this stub up 3 levels to the roof? As the plumbing diagram shows, there is no vent that is accessible in the basement level. Would the fact that this basement stub system being located up from the main exit drain not require me to vent this basement bathroom. Do the vents that are used in the main and upper floor bathrooms work for this type of layout?

I'm confused as to why my builder wouldn't vent the basement bathroom.

Can someone help clear this up?

Thanks in advance.

Termite 09-19-2008 11:11 PM

Yes, you definately need to vent that bath group. You can probably get that done fairly easily utilizing the vertical vanity pipe.

Most of the time, the plumber will stub a vent in the unfinished basement up in the ceiling and cap it off...If he's worth a darn. It may not be even close to the bath group, but it should be there. If not, that's a shame!

If there is no vent stub, you can use an AAV vent (air admittance) in the wall above the sink.
Here's the link.
Most plumbing supply houses will have them. Make sure your local codes inspector will allow their use.

AAV's are great, and they work. But, they have to be installed in such a way that they are accessible, and they must be able to breathe. Ideally, the back side of the wall is unfinished basement. That gives easy access and plenty of air to breathe. I've allowed their installation in fully-sheetrocked walls, but require an HVAC grille on one side of the wall at the vent's height to allow for access and airflow.

ameleus 09-20-2008 07:20 AM

I have seen and followed up on the Studor Vents, they sell them in hardware stores here in Atlanta so I would assume that the local codes allow them. I'll confirm by reading the plumbing code as needed.

Would it be better to have this on the exterior of the house instead of contained in the basement? Would I have to tie in the bathtub's waste plumbing into this vent too or would the fact that it's connected under grade be good enough? I've seen these Studor Vents installed under a vanity's sink which is enclosed in the cabinetry of the vanity itself. Is this typical? My understanding of a vent in general is not only to let are in but let air out too. These Studor Vents don't allow the escape of air. I guess letting air out of a vent isn't the way it works?

Thanks for your reply.

Termite 09-20-2008 09:08 AM

They only let air in. Hence the name Air ADMITTANCE Vent. You will not get sewer gas coming out of them. They cannot be installed outdoors.

Yes, a fairly normal installation is behind the sink in the vanity. They need to be above the drain level of the sink.

Be sure that your codes folks allow them. Unfortunately, they sell a lot of things that aren't necessarily allowed by all building departments. I think it is ignorant not to allow them...I do, provided they're not being used as a crutch by someone who has a reasonably easy means of hard-piping a vent to the roof.

ameleus 09-20-2008 10:28 PM

Thanks for your input... I (financially) enjoy what I'm hearing... Using this Studor Vent type system... must I use one for each of the drains in this stub unit (3) or will that "vanity tube" within the wall studs work for all the drains together?


Termite 09-20-2008 11:05 PM

It is very difficult to tell for sure. I would imagine that the vent in the wall will take care of all of it. You normally don't see basement baths vented any other way.

Is there a trap below the gravel at the tub/shower drain location? There needs to be. The reason I ask is that there's a 12" section of vertical pipe sticking out, which is odd. It could be the vertical leg off the trap, or it could be a vent. You'll need to dig down to check that out.

ameleus 09-20-2008 11:40 PM

yes.. confirmed that that drain (boxed out for the tub) does have a trap.. I haven't confirmed the one in the stud walls. At this point, I don't think that matters..

Thanks for the help. I'm sure I'll be back here when the copper subject comes in.

Termite 09-21-2008 10:26 AM

Right, your vanity's trap will be installed under the sink later on.

Copper...I/we can definately help. Just holler!

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