Critique this layout...

Beachfront71 · Jun 17, 2011

Double Sink / Share DWV pipes? UPC/California

Hello and thanks,

Can anyone give me a quick yes or no on the UPC / California code with regards to double sinks in a bathroom?

Specifically, can we run one drain and vent and branch off of that to the 2 sinks as oppossed to running seperate drains down and vents up for both?

I can not find any info regarding this per code?

Thanks,

hj · Jun 18, 2011

quote; Specifically, can we run one drain and vent and branch off of that to the 2 sinks as oppossed to running seperate drains down and vents up for both

The question is NOT whether you can do it, but rather HOW you do it. In most cases that is how a plumber WOULD do it, but it has to be done properly, not just start putting fittings together and insert a tee wherever you want a sink.

Sponsor · 2022-01-29T12:20:58-0800

Beachfront71 · Jun 18, 2011

thanks HJ,

A plumber is doing the work, I just read a short blurb that IPC allows it but UPC does not .. that is where the confusion was at ..

Terry · Jun 18, 2011

California uses UPC code.

The comments I've seen about adding tees on the horizontal, I haven't seen that done on the West Coast. That's an East Coast IPC thing.

Tom Sawyer · Jun 18, 2011

Maine uses the UPC. You can indeed use one single drain/vent for double lavs provided your distances are correct. remember that this section of piping is the trap arm.

To help clarify this; It would be a major hassle to pile a 3 bay culinary sink if you had to separate the drains.

Beachfront71 · Jun 18, 2011

thanks for the info ..

would this same thing apply to both double bay sinks as well as 2 seperate sinks .. say 3 feet apart?

Tom Sawyer · Jun 18, 2011

yes........................

hj · Jun 18, 2011

quote; I just read a short blurb that IPC allows it but UPC does not .. that is where the confusion was at ..

IF the installation is done properly, the both codes allow it. IT is a specific "improper" installation that the IPC allows, but the UPC does not.

Plumber2011 · Jun 19, 2011

Hi Beachfront...

Assuming 2 lavatories, side by side, in California, the following picture showing ABS (black) plastic piping materials should demonstrate appropriate piping requirements. In most cases, the elbows will want to come out of the wall at about 18", so be sure to figure for that while remembering the 1/4" pitch per foot of piping needed for proper drainage. In CA, apparantly you guys can use the double combination wye fitting...in my area, the fitting must be a double sanitary tee fitting (see picture with PVC (white pipe) fittings).

Double check with your plumber, of course!!

Good luck!

PS: Terry, I don't know anywhere on the East Coast that uses sanitary tee fittings on the horizontal for drains....for vents, yes, but not to pick up drains! PA may be an exception, but PA has some super crazy codes and they don't count!...

Yersmay · Jun 19, 2011

question

I am posting in the spirit of advancing -- hopefully not hijacking -- this interesting thread.

Plumber 2011, I'm curious why your area requires a double sanitary t, instead of a double combination Y. What does a double sanitary 't' have to offer that double combination 'y' can't accomplish? In fact, to my uneducated eye, it would seem that a double combination 'y' would have less cross flow than a sanitary 't'. If there is a concept to learn about how these two fittings drain somewhat differently, I am very interested to hear. Thank you in advance!

Tom Sawyer · Jun 19, 2011

When you use a wye, either single or double, with proper pitch and distance it possible for the trap weir to be above the wye inlet which creates an S trap.

Plumber2011 · Jun 19, 2011

Yersmay...good question.

In fact, many inspectors dislike the double sanitary tee fitting as they argue a snake could cross over and into the other sink, but it is code and as Tom said, "with proper pitch and distance it's possible for the trap weir to be above the double combo. wye inlet which creates an S trap". The double combo. wye, in effect, reduces the contribution of the vent, but still legal in many areas.

See the image below for more clarification. Note here, that the picture is clearly exaggerated to drive home the point, but it should help...

Beachfront71 · Jun 19, 2011

Thanks to all for all the info .. it is appreciated.

Beachfront71 · Jun 19, 2011

Prob a dumb follow up question but when building a wetwall directly in front of another existing wall is there any condensation issues that would come up with leaving the existing drywall on the wall that will end up behind the wetwall?

This is a bed to bath conversion that will be inspected ...

Just thought I would ask as a wetwall is now required due to a beam location...

THanks again ..

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