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Thread: Basement bathroom venting question

  1. #1

    Default Basement bathroom venting question

    I had a new turn key house built 2 years ago and had them rough in for a half bath. I have the toliet pipe and sink stack stubbed in the floor. I am finishing the basement now and am going to start the plumbing. I don't see any vent roughed in. I called the company that built our home and they say it's vented in the slab to the main house stack.

    1) Can you vent plumbing in the slab and if so how does that work?

    2) I want to install another sink about 10' away from the bathroom sink, how can I hook into the under slab vent? ( I have no problems draining, I am just going to tee into the sink stack that is stubbed, just not sure about how to vent that using the under slab vent???)

    Any help here would be appreciated.


  2. #2


    Do you have any pix of the drain/vent b4 the concrete was poured?
    If not, does the township have the diagrams? It seems odd that they wouldn't require the fixtures to be individually vented. You should really call the township construction offc and confirm that it was done right.

    As for the second sink, tie into a vent above ground.

    Do you have a sewage pump or below-grade draining? If it's a pump, the vent for the pump should be easily accessible (assuming they vented that).

  3. #3


    I don't have pictures of the piping before they poured so I'm not sure what that looks like.

    I don't have a sewage pump, everything is high enough that it all flows naturally to the septic tank.

    My bathroom in the basement that I am installing is on the opposite side of the house where the upstairs bathrooms are. Same thing goes for the kitchen sink. My basement bathroom is below the living room and bedrooms.

    So if they did indeed vent the basement bathroom in the slab then there is no way to hook into that vent?
    Would I have to run another vent up through the attic to the main stack then for the second sink?

  4. #4


    For a sink, your code might permit an air admittance valve. If you're permitted to vent under the slab to the main stack, then why wouldn't you be able to join it above ground?
    Last edited by prashster; 03-06-2006 at 01:43 PM.

  5. #5


    I made contact with the plumber that installed my plumbing and he said that my bathroom is vented in the slab. It's called a wet vent. He said I will need a Studor Vent (or Auto Vent) hooked up at the sink. The same thing applies to the Bar sink that I want to add on the same wall. I can drain the bar sink into the bathroom sink by adding a tee to the bathroom tube.

    Thanks for you help prashster.

  6. #6


    I defer to the expert advice of your plumber, but...

    check with your construction office whether Studor or any type of air admittance valve is permitted. I've read a lot of stuff on this forum about how studor vents are not very reliable (perhaps they ARE on a sink, though), and how a lot of plumbers swear away from them.
    Last edited by prashster; 03-07-2006 at 05:39 AM.


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