View Full Version : Connecting branch lines to building drain

07-16-2012, 03:58 PM
Is it acceptable for two branch lines to connect to the building drain using a 45 degree wye fitting with the branch inlet rotated up? One branch line is for two bathrooms and uses a horizontal wet vent. It is about 8" higher than the branch line for the kitchen sink and laundry room. Hopefully this drawing makes it clearer but my isometric drawing skills have left me. The house is a single story over a 30" high crawl space.


07-16-2012, 04:21 PM
A Y can be in ANY position from horizontal on the left up and over to horizontal on the right. Whether it is in a proper position depends on WHAT is connected to it and HOW that piping is arranged. Your shower is NOT vented, and I am not sure HOW you are getting from those two lavs to the vertical vent or whether they also need individual vents.

07-16-2012, 06:45 PM
Thanks for your feedback hj. I've either made a mistake in my design or my drawing. My understanding of the horizontal wet vent for a bathroom group under IPC 2006 was that the shower would be vented by the vertical vent just as the WCs and the bathtub. The bathroom branch drain is 4" and its length is less than 10'. The branch drain for the lavs is 2" and its length is less than 5'. Does that change anything?

07-17-2012, 08:38 AM
As soon as you run the toilet drain past the shower connection, you create the need for an individual vent. THe only thing that changes is that IF the two sinks are connected to a "twin elbow", not a tee which would be incorrect, then you have a poor installation, which will be impossible to snake when it plugs up.

07-17-2012, 02:08 PM
Thanks again hj. The wet vent code is real confusing. I have seen where some states, e.g. California, require the toilet to be the last fixture on the wet vent. However, Georgia has no current amendments to the 2006 IPC which does not require it. The International Code Council has an article on their website that discusses venting. The link is http://bsj.iccsafe.org/june/inside_icc/pmg_plumbvents_part_3.html

Hopefully it's OK to include this diagram from the article.


The article is based on IPC 2009 but there is not a significant difference in the wet venting code between IPC 2009 and 2006 which GA uses. Am I misreading the code? Would you still suggest venting the shower? Or I could redirect the shower drain upstream of the toilets but it would require 135 degrees in bends.

Your point about the double elbow on the lavs being a poor installation is spot on. I have a similar setup currently and you're right to say "when it plugs up". But this is also where there is more confusion on the wet vent. I have read that if the lavs have a common vent, it must connect downstream of the wet vent. But I have also read that it doesn't matter. I have talked to plumbers in the area and there is no consensus. I looked at the lavs having a vertical drain but the wall is directly over a double floor joist. Are there alternatives to the double elbow? Could the lav branch arms be offset horizontally? I'm looking for a better alternative if you have any suggestions.

07-17-2012, 03:05 PM
not sure about your code but your drawing, and the one you used from the article would not comply with our code.

Tom Sawyer
07-17-2012, 05:32 PM
IPC will let you wet vent "BATH GROUP" fixtures in any order now. You can only wet vent bath group fixtures. No kitchen sinks, laundry trays, washer boxes etc. They also say that the vent for toilets can be an unlimited distance from the fixture which pretty much means a vent somewhere in the structure.

07-18-2012, 04:11 AM
Thanks for clarifying that Tom. So the bathrooms' branch drain and the wye connecting it to the building drain appear to be code worthy. Are there any better options for connecting the back to back lavs besides using the double elbow?

07-18-2012, 06:58 AM
The IPC is a "code of convenience". It appears that if someone has a problem and has found an "easy way" to fix it, it goes into the code that way. The shower AFTER the toilet would not be vented with a "good" code.

07-18-2012, 10:35 AM
The shower AFTER the toilet would not be vented with a "good" code.

I would never run a toilet by a shower. The shower should have a vent before bringing it in to the main line.
But then I'm on the West Coast, where we still do things right. We can still afford a few bucks in fittings.

07-18-2012, 03:31 PM
I have read a lot of posts on this website over the past year and have been impressed by the advice that was given. I appreciate your expert opinions and that's why I posted my question here. I have no problems with doing it "right" even though I'm not on the "left" coast. Would having the shower drain enter upstream of the toilets be a "good" solution or just another cheap shot? It would require bends of 135 degrees to do that. Otherwise, the shower drain branch arm can be extended further downstream and an individual vent can be added.

07-18-2012, 05:38 PM
It depends on where your walls are as to what would be best.
A shower drain needs venting within five feet. Most showers have walls that I can use to hide vents.

By the way, I was in an old home yesterday, with an unvented tub downstream of the toilet. When the toilet flushed, the water in the tub trap was moving. Not good.

07-18-2012, 08:00 PM
Thanks Terry. The bathrooms are back to back and each is 5' x 8.5'. The shower is 30" x 60" with a center drain. The long wall is external but there are 2 x 4 walls on each end. So the five feet to the vent is not a problem. The shower trap arm could be routed opposite to the direction shown in my original drawing and connect to the bathroom branch drain upstream of the lav wet vent. This would be the choice if the wet vent is an acceptable vent. But if you think an individual vent is best overall then I could route the shower trap arm downstream, vent it through the end wall and connect the drain directly into the building drain.