I'm in central Virginia, my home is 9 years old. I have drain lines for a bathroom roughed in in the basement. 4" WC stubbed out, and tub drain with p trap visible through slab via 6" x 12" box out in slab. There is a sink drain stubbed out as well. There are 3 waste stacks from the main floor running down through the slab. The closest is 10 ft. from the sink drain (the farthest drain from that stack).

My question: How are these drains vented. Should vents have been roughed in or will I need to add vent(s) as I finish the bathroom? Need help. Thanks!

Hi 435studio...

I'm betting that the lavatory (sink) pipe is 2" pipe. If this is the case, then I am pretty sure that they have WET VENTED all the bathroom fixtures.

Here, the lavatory vent, which must remain 2" all the way until it connects into a 2" vent or larger, acts as the vent for the lavatory, the tub and the toilet. This is permissible in 90% of the country if piped correctly.

Let me know if this sounds right..

MARK

Thanks Mark. Yes, lav pipe is 2", tub drain is 2" also.
Can you give me a little more to go on as far as "Wet Venting." Does that mean that the drain pipe from above serves to connect these lower level drains to the venting system?

Yes...

The lavatory drain comes off the toilet pipe underground and then runs by and picks up the tub before coming out of the ground as the lavatory drain. From there the lavatory gets piped up and then the vent runs, as mentioned, up to meet another 2" vent (or larger) in the attic or even a bathroom above...

The idea here is that people usually do not use the sink when they are flushing toilet or draining the tub so the lavatory vent, having been increased from 1.5" to 2" (why it must remain 2"), will act to vent each fixture. That is of course, unless you like to go potty and wash your hands at the same time... ;)

Let me know if that made sense...


MARK

Thanks, I think I'm getting it. So based on what I have described there is no need for additional venting, or do I need to install a vent as an extension of the lav drain pipe?

You must run a 2" vent off the lavatory pipe. That vent must connect into a 2" vent or larger in the attic... unless you can find a FUTURE VENT in the basement and then you can connect the 2" vent from the lavatory to that.

Look around for a TY fitting with a cap or cleanout in the basement ceiling... should be marked as FV if it is present.

Otherwise, after you stub out for the lavatory run that 2" vent vertical and connect into a 2" or larger vent in the attic... OR, you could also penentrate the roof separately with the 2" vent if you find roofing work easier than plumbing... ;)

Check out the pic. Below.. should explain the rest.

Keep 'em comin' if you like...

MARK

Exceptional! You've provided exactly what I needed. Thank you! I think I'll look for an existing vent to connect to, I don't need a leaky roof to deal with...

Good luck!

I found a vent that runs vertically up from the master shower drain line directly above the basement bath rough in. I assume that I could run my new lav vent up and connect to that vent. However, the existing vent runs up through the floor, inside an interior wall, and out through the roof. I'm not sure how I can get access to connect to that vent. Is it possible to somehow connect the new lav vent to the shower drain line? Or is there a better solution. Thanks!

Hey hey...

That shower vent is probably only 1.5"...not large enough for a the basement bathroom vent that is 2". And, no you cannot connect the downstairs vent into the upstairs shower drain... nice try! See if you can find a 2" vent in bathroom above this or run a 2" vent past that bathroom up and into attic and join a 2" or larger vent up there.

Don't hesitate to ask more questions if you think you've found something that could cut cost/labor down.. Glad to answer.

MARK

Thanks again; I'm venturing into the crawl space and attic this evening to see what I can find!

Let me know what you find here. Look at closets and see if you can find a way to get the pipe from the basement installing the 2" vent pipe to the corners of closets..?

Anything you think of may help.

Mark

I found the vent from the bathroom in our hallway. It is a 2" vent, but it runs up an interior wall. We have cathedral ceilings and the access hatch is on the other side of the house from the vents. I could possibly get to the vent in the attic, but it would be a struggle.

I'm also going to want to vent a sink in a wet bar in the basement as well. Are there any other alternatives? I'm kind of stuck right now. Any suggestions are welcome!!

You said you found a 2" vent in bathroom above...can you get basement vent connected to that?? Here, you would open the wall upstairs and connect into that 2" vent at 48" off the floor... any chance?

In terms of the wet bar... you can run the vent for the bar-sink and connect into the vent from the BASEMENT bathroom... as long as a minimum of 48" off finish floor (of basement) or as high as you want...

Let me know...

Thanks so much for sticking with me on this... I was trying not to disturb anything upstairs if at all possible. Actually, I may be able to get to the vent through the wall behind the mirror in the master bath. (That is probably my best bet, I should be able to drill through the floor to get to it.) I have to connect the new bent at least 48" above the master bath floor, correct? Then the vent from the bar sink can connect to that vent pipe in the basement, at least 48" off basement floor?

You understood perfectly!

Good idea on looking behind the medicine cabinet... ;)