Question about tying in to old work

All,

Please review the attached image. I am removing a BT in a 2nd floor bath and putting a double LAV in its place. I planned on tying in to the existing 2" drain/vent that serves the hall bath (and served the old BT) and the LAV in the 1st floor bath. However, after more research I find that the 2" drain has a horizontal bend in it. I thought the drain ran vertical to the basement where it ties in to the building drain, but it does not. The horizontal section is there b/c the walls on the 2nd and 1st floors do not align - they are 14" off.

Note: I do not know yet how the LAV on the first floor bath ties in to the 2" vertical (sani-tee or wye, etc.). If that is a critical piece of information, I'll have to bust into the wall to see.

I have 2 questions:

1. Is this setup (in part or whole) goverened under Section 912 the 2009 IPC (Combination Drain & Vent System), Section 909 (Wet Venting), or both?

2. Based on what I've drawn and described, can I tie the double lav in to the 2" as-is using a double sani-tee, or do I need to have a separate the drain and vent?

Thank you in advance for your time.

Once a pipe becomes a vent, you cannot use it for a drain. SO, your drains from the second floor need to go down below where the vents from the first floor originate so they can remain vents.

You can put in a double-fixture arm for the lav's. A drain can go horizontal (with at least the minimum slope), but there are also limitations on how many turns it can take and how far it runs.

See what the pros have to say...

jadnashua said:

Once a pipe becomes a vent, you cannot use it for a drain. SO, your drains from the second floor need to go down below where the vents from the first floor originate so they can remain vents.

You can put in a double-fixture arm for the lav's. A drain can go horizontal (with at least the minimum slope), but there are also limitations on how many turns it can take and how far it runs.

See what the pros have to say...

Click to expand...

Thanks jadnashua. I appreciate the feedback!

drain

The fact that the tub is connected to that pipe implies that the downstairs sink is vented properly, but that could only be verified by opening the wall or doing some additional detective work. You need a "back to back fixture fitting", (but you will turn it sideways and insert two 1 1/2" arms into it), and also a cleanout in the pipe beneath that fitting.

Dvw

hj said:

The fact that the tub is connected to that pipe implies that the downstairs sink is vented properly, but that could only be verified by opening the wall or doing some additional detective work. You need a "back to back fixture fitting", (but you will turn it sideways and insert two 1 1/2" arms into it), and also a cleanout in the pipe beneath that fitting.

Click to expand...

Thanks hj.

A question regarding the cleanout... I was planning to put a cleanout on the 2" tub drain after I cut it back and add a 90 to where it will turn up about 15" from the wall. That way I can conceal the cleanout with the middle vanity cabinet with a hole cut into the bottom of the vanity for access. I was going to do this just in case the wye that the old tub drain fed into gets clogged in the future.

Do I need both cleanouts (which seems overkill), or just the one you recommend?

Also, this may be a stupid question, but can a wall cleanout be hidden behind a cabinet, or do I need an access panel cut into the cabinet to pass inspection?

co

You only need one. The closer it is to the sinks the more effective it will be. You can put it anywhere you want to, as long as the plumber can get to it to unscrew the plug. I usually turn it so it faces the room behind the sinks for maximum accessibility.

nhmaster said:

Too bad he's so far away. We could all show up and show him how to do it free of charge. For god's sake. This is a major plumbing job here. It needs to be designed and executed by a trained, licensed plumber.

Click to expand...

Why? So they can drill through the bottom 1/3 of the joist and run a 3" drain?

hj said:

You only need one. The closer it is to the sinks the more effective it will be. You can put it anywhere you want to, as long as the plumber can get to it to unscrew the plug. I usually turn it so it faces the room behind the sinks for maximum accessibility.

Click to expand...

Thank you.

This will be my last post/question on this site. Thank you for sharing your knowledge with me. I truly appreciate it.