Venting bathroom in basement finish

[stkn]

Hi all,

I'm a DIY-er with a lot of experience in some phases of construction but not much in plumbing (so please be nice to my dumb questions!). I'm finishing a basement with a full bathroom, and thought I'd toss out a question here as I ponder whether to attempt myself or hire out.

My question is about venting. When they built the home 2 years ago, they roughed in for a bathroom in the basement. I'll put a picture below of the rough in. In the picture, from left to right, is a drain pipe for the lav (it is right up against the insulation), then the toilet, then the drain for the tub. But, I can't find any evidence of a vent. There's no rough in for a vent in the ceiling anywhere, and the only stack in the vacinity is 3.5 feet from the tub drain, but I know it is draining the 1st floor laundry (and possibly others as well). Any ideas on how to vent this without having to run a new vent to the roof (which would be near impossible)?

I *think* my local code allows AAV venting (as I'm pretty sure my kitchen sink has one, though the other bathrooms in the house do not). However, even if I did that for the lav, what about the toilet and tub? Is it at all possible that the stack draining the laundry could be used as a wet vent for any/all of the basement bathroom fixtures? (I'm pretty sure it's a "no", but thought I'd ask.)

 

[hj]

That "stack" cannot be used as a "wet vent". I cannot imagine any "competent" plumber would install all the piping and NOT connect the vent, or at least make a vent available.

 

[Sponsor]

 

[stkn]

Thanks. I realize I'm exposing my own incompetence here, not the original plumbers! Despite our builder having a strong reputation in the area for being cheap and corner-cutting, I'm sure the rough-in was at least up to code. Mostly I'm just trying to ensure I have correctly identified/understood how the venting is currently configured, so that I know what I do or don't need to do should I decide to attempt installing the bathroom plumbing myself. I've scoured the walls and ceiling for a vent connection, but I'm pretty sure there's not one. A friend recently suggested to me that the toilet and tub drains are likely configured to wet vent through the lav pipe (which is 2"). In that case, as far as I can tell, I would need to install an AAV in the sink cabinet, and that AAV would vent the whole bathroom group. Does that sound like a typical configuration, or is it more likely that I'm just too incompetent (!) to identify a roughed-in vent connection somewhere in the basement? (I don't love the idea of using an AAV, but it is allowed in my local building code.)

 

[Stuff]

Normally that is how things are laid out for this kind of rough in - sink wet venting bath and toilet. Assumed vent could connect to something overhead in another part of basement (above washer?).

Thing is you are guessing. You need to figure out what is there before proceeding. Snake/scope/metal detector/run water to figure out what is connected to what.

 

[stkn]

Thanks! The washer is on the 1st floor, so the only plumbing fixtures in the basement are the water heater (and floor drain) and those in the roughed-in future bathroom. I've looked all over in the floor joists overhead for a vent connection, but there doesn't seem to be anything. Only plumbing I can find are drain stacks for the 1st and 2nd floor fixtures. This is what makes me wonder if the plumbers intended for an AAV to be used.

I agree that I'm guessing a bit right now. I have requested the plans from the city building department, so that will hopefully shed some more light.