I have a rough in for a full bath in my basement.
House was built in 2000 in Pa. Two story colonial.

I can locate two vents from the 1st floor bath. One 2" vent right of the WC drain and one 1.5" off the shower on the first floor. There is a 2nd floor bath over the first. I can hear the 2nd floor bath as it drains into other pipes so I'm sure these are truly vents.

I would guess the 2" vent would be best. My question is how far up do I need to go to put in a T to vent the basment bath? I only have about three inches before it goes into the 1st floor subfloor. Is this enough?

One more if you please.

There is an opening in the concrete floor with a horizonal 2" pipe for the tub/shower. Do I dig down below it to install a P trap or can I install the trap above it?

Thanks for help,

Windoor

All fixtures having a trap have to be vented. You should have a vent coming off the lavatory and the shower should be wet vented off the lav drain.
As for venting the basement rough in you vent off the tee that you pick up the lavatory with. You have options here. If you decide to run a vent pipe you must run it up to a inverted tee that you must cut at least 6" over the flood rim of the highest fixture. A much easier solution would be to install a AAV (Air Admittance Valve) in the Lavatory tee you were going to take the vent off from. A AAV is a mechanical vent,(see below) and if you wish to know more about them click on back.
The dap out,(hole ) in the cement is there for a bathtub to connect to and there should be a trap already there with a vertical raiser coming up out of it. You shouldn't have to install a trap. Good luck, tom

The 2" bath drain pipe is horizonal under the floor with no vertical riser. I'm pretty sure there is no trap as it runs under the floor towards the main stack.

The lav drain is a 2" vertical pipe behind and to the right of the WC rough in. It is set to go into a future partition wall under the steel beam. I gave the plumber a rough sketch as to how I would lay out the bath at the time of build. Don't think I want to bury a mechanical vent in a wall in case there is problems with it in the future.

I have a digital camera and will post pictures later today. Maybe that will give more insight as to what I'm working with.

Thanks for your response.

Windoor

Hey Windor,

"There is an opening in the concrete floor with a horizonal 2" pipe for the tub/shower. Do I dig down below it to install a P trap or can I install the trap above it?"

You dig down to it and install the trap and raiser to the horizontal drain.
For a bath tub the average measurements are. 15 1/2" off the back wall to the center of the trap raiser and 1 1/2" off the front wall to the center of the trap raiser.
If you're going to install a tile shower then the drain can be placed anywhere you wish but if you plan on using a manufactured shower enclosure you'll have to get the correct drain measurement to locate the raiser.
You'll have to run the bathroom vent off the lavatory and run it up to tie into a existing dry vent with a inverted drainage tee at least 6" over the flood rim of the highest fixture. I'll be interested in seenig your pictures. Regards, Tom

Thanks for the advice. I plan on framing the end wall and the wall under the I beam. Then set the tub before framing the back tub wall. This will allow me to get the trap set right. Using a Kohler Acclaim tub and shower walls.

I was talking to a plumber out of Carroll Co. Md and he suggested using the 1.5" vent of the first floor shower rather than the 2" off the WC. He says it's legal to use a 1.5" vent in his county, but doesn't know about PA.

Because no one uses the first floor shower, if anything should back up I won't have a problem in the future.

Links to bath rough in.

http://www.we-todd-did-racing.com/wetoddimage.wtdr/wMTExMDE3NjZzNDEzZGZkMzF5NTQx.jpg

http://www.we-todd-did-racing.com/wetoddimage.wtdr/wMTExMDE3NTZzNDEzZGZkMzF5NTQx.jpg

http://www.we-todd-did-racing.com/wetoddimage.wtdr/wMTExMDE3NzZzNDEzZGZkMzF5NTQx.jpg

1.5" vent off 2" 1st floor shower drain. T off this for basment vents? (http://www.we-todd-did-racing.com/wetoddimage.wtdr/wMTExMDE3ODZzNDEzZGZkMzF5NTQx.jpg)


Windoor

This show the 1.5" vent off the 2" shower drain. You can't see it but the shower drains to the left into a 3" drain that runs over to the main stack.

1.5" vent off 2" 1st floor shower drain (http://www.we-todd-did-racing.com/wetoddimage.wtdr/wMTExMDcxMjZzNDEzZGZkMzF5NTQx.jpg)

The 2" drain that runs over to 3" carries the 1st floor lav and 2nd floor lav and tub. (http://www.we-todd-did-racing.com/wetoddimage.wtdr/wMTExMDcxMzZzNDEzZGZkMzF5NTQx.jpg)

windoor

I would have roughed it in differently using one 2" vent off the lavatory to vent the group but perhaps your local codes don't like wet vents. Inspectors like to see 2" vents even if code doesn't call for 2". I found that out when I was foreman on a large church job in south Florida. (3 kitchens and 13 bathrooms). I got passed but he wasn't too happy about it. Where's the vent off the lavatory? Cheers, Tom

Ok, you talked me into it.

I can cut a hole in the upstairs bath wall above the W/C. Looking at where the 2" vent goes up from the basement and locating the studs in the bath, it looks like I'll have room to make it work.

Invert Y into existing 2" vent above the 1st floor lav (at least 6") and drop a 2" pipe back down to the basment. If my drywall finishing skills aren't up to the task, (always shaky with cut outs) I'll buy a cabinet to go over the W/C and cover the scar. This should make everyone happy.

The lav vent will go into the yet to be framed wall under the I beam and tie into the now 2" vent with everything else.

Plan on starting tomorrow with the framing and I know where to come if I get into trouble with the plumbing.

Thanks so much for your help.

Windoor