I am adding a second bathroom group to my one story home. This group has a separate drain line that exits the home and ties into the main sewer drain line out in the middle of the yard before it goes into the city sewer. My question is can I revent this group back to the main stack instead of punching another hole in the roof?

I am adding a second bathroom group to my one story home. This group has a separate drain line that exits the home and ties into the main sewer drain line out in the middle of the yard before it goes into the city sewer. My question is can I revent this group back to the main stack instead of punching another hole in the roof?

Yes you may. You can run the new vent up in the attic and revent back into the main stack. Don't forget when you do that the fitting that ties into the stack must be inverted and the entire vent sloped back to the source.
Good luck, Tom

Yes you may. You can run the new vent up in the attic and revent back into the main stack. Don't forget when you do that the fitting that ties into the stack must be inverted and the entire vent sloped back to the source.
Good luck, Tom


Thank you for your earlier response to my question on venting. My plumbing inspector is a very easy going guy to the point of I don’t think it matters to him if I am doing it exactly right or not. I have a few more questions, just to ease my mind.
Here’s my situation. I’m add a new master bedroom bathroom and laundry in a room adjacent to the new bathroom.
The toilet is furthest upstream and is connecting with a 3” PVC, neo angle shower ties in to the 3” line with a 3x3x2 wye, then the washer connects to the 3” with another 3x3x2 wye, then the lav connects with a 3x3x1 ½ wye then the 3” exits the building to a 4” waste to the road.
My uncertainty remains with the placing of the vent for the group. Can the vent be 1 ½”? I would like to place it in the wall next to the washer drain. When venting a group like this how do you measure the allowable distance from the vent to the trap? Is it straight line from the trap to the vent connection or do you follow the pipe? My lav trap is farther than 3 ½’ to where I would like to place the vent. Do I need to vent closer to the lav?

I have a lot of respect for plumbers. I’ve been remodeling this old house for three years and if I had to pay to do this it would never get done in my lifetime. Thanks for any advise you may have.

1)"Can the vent be 1 ½”?"
Section 1412.3 of The Standar Code book mandates a 2" vent
2) "When venting a group like this how do you measure the allowable distance from the vent to the trap? Is it straight line from the trap to the vent connection or do you follow the pipe?"
Per Section 1409.3 The distance is measured along the developed length from the the traps weir( The back of the "U") to the vent opening so it would be follow the pipe.
The distances are 1 1/4" = 2 1/2' *** 1 1/2"=3 1/2' ***2" = 5'
3) "My lav trap is farther than 3 ½' to where I would like to place the vent. Do I need to vent closer to the lav?"
Yes, if you plan on a 1 1/2" drain line and no if you drain it with 2".

Good luck on your project, Tom

1)"Can the vent be 1 ½”?"
Section 1412.3 of The Standar Code book mandates a 2" vent
2) "When venting a group like this how do you measure the allowable distance from the vent to the trap? Is it straight line from the trap to the vent connection or do you follow the pipe?"
Per Section 1409.3 The distance is measured along the developed length from the the traps weir( The back of the "U") to the vent opening so it would be follow the pipe.
The distances are 1 1/4" = 2 1/2' *** 1 1/2"=3 1/2' ***2" = 5'
3) "My lav trap is farther than 3 ½’ to where I would like to place the vent. Do I need to vent closer to the lav?"
Yes, if you plan on a 1 1/2" drain line and no if you drain it with 2".

Good luck on your project, Tom


Sounds like I want to drain the lav with the 2" drain so I can vent where I want to. If I do use a 2" drain on the lav does the lav trap need to be 2" as well or can I reduce where it comes out of the wall to meet the trap?

Thanks for the help!

Isn't he still discharging the toilet past the shower before the vent comes in?

Isn't he still discharging the toilet past the shower before the vent comes in?

My bad! I fixed on the vent question and ignored the drainage set up. Thanks for setting me straight.

"The toilet is furthest upstream and is connecting with a 3” PVC, neo angle shower ties in to the 3” line with a 3x3x2 wye, then the washer connects to the 3” with another 3x3x2 wye, then the lav connects with a 3x3x1 ½ wye then the 3” exits the building to a 4” waste to the road.. My uncertainty remains with the placing of the vent for the group.
I misunderstood the question. I thought you were asking if you could revent back to one vent and then run it up to the attic and revent back to the roof vent. EVERY FIXTURE that has a trap must be vented or wet vented. The washer, lav and shower must all be vented. You can avoid running a separate vent for the shower if you configure it to drain into the lavatorys drain where it will be wet vented. Both the lav and washer need vents installed.
Thanks again DC for being so sharp on picking up on this error. Tom

My bad! I fixed on the vent question and ignored the drainage set up. Thanks for setting me straight.

"The toilet is furthest upstream and is connecting with a 3” PVC, neo angle shower ties in to the 3” line with a 3x3x2 wye, then the washer connects to the 3” with another 3x3x2 wye, then the lav connects with a 3x3x1 ½ wye then the 3” exits the building to a 4” waste to the road..My uncertainty remains with the placing of the vent for the group.
I misunderstood the question. I thought you were asking if you could revent back to one vent and then run it up to the attic and revent back to the roof vent. EVERY FIXTURE that has a trap must be vented or wet vented. The washer, lav and shower must all be vented. You can avoid running a separate vent for the shower if you configure it to drain into the lavatorys drain where it will be wet vented. Both the lav and washer need vents installed.
Thanks again DC for being so sharp on picking up on this error. Tom


Tom, I believe you have answered my direct questions very well. This is a small bathroom arrangement. I’m wondering why all the fixtures can’t vent on the same vent. The toilet on a 3" drain would be less than 7' from the 2" vent. The shower is on a 2” draining into the 3” just down stream from the toilet. The washer branch would be vented, it too would be 2” draining into the 3” then the lav would drain in on a 2” branch just after the washer. If all the fixtures fall within the maximum allowable distance between trap and vent ( which they would seem to) then do you see a problem? My other bathroom only has one vent for the group, toilet, tub, 2 sink lav. I’ve attached a file showing the layout if you would like to examine the layout.

Tom, I believe you have answered my direct questions very well. This is a small bathroom arrangement. I’m wondering why all the fixtures can’t vent on the same vent. The toilet on a 3" drain would be less than 7' from the 2" vent. The shower is on a 2” draining into the 3” just down stream from the toilet. The washer branch would be vented, it too would be 2” draining into the 3” then the lav would drain in on a 2” branch just after the washer. If all the fixtures fall within the maximum allowable distance between trap and vent ( which they would seem to) then do you see a problem? My other bathroom only has one vent for the group, toilet, tub, 2 sink lav. I’ve attached a file showing the layout if you would like to examine the layout. Crude sketch with drain lines indicated.

"I'm wondering why all the fixtures can’t vent on the same vent?"
They can if all the fixtures are vented. However, you are still discharging a major fixture, (the toilet) past a unvented minor one,(the shower). This is against code and will not pass inspection.
You canget around this one of two ways. (1) run a separate vent off the shower **or** (2) connect the shower drain to the washer drain and let it be wet vented by the washers vent. If you go with door#2 you may then tie the washer vent back to the lavatory vent and run a single vent up to the attic where it will revent back into the vent out the roof. Sound like a plan?
Regards, tom

"I'm wondering why all the fixtures can’t vent on the same vent?"
They can if all the fixtures are vented. However, you are still discharging a major fixture, (the toilet) past a unvented minor one,(the shower). This is against code and will not pass inspection.
You canget around this one of two ways. (1) run a separate vent off the shower **or** (2) connect the shower drain to the washer drain and let it be wet vented by the washers vent. If you go with door#2 you may then tie the washer vent back to the lavatory vent and run a single vent up to the attic where it will revent back into the vent out the roof. Sound like a plan?
Regards, tom

Got your drawing... Door #2 it is then. If that's what it has to be. Looks like I'll be using a lot of 2" pipe. Can the trap on the lav be 1 1/2"?

Jerry

Hi Jerry,
"Can the trap on the lav be 1 1/2"?" Yes, you may pick up the lavatory off a 2 X 2 X 1 1/2" drainage tee. Good luck, Tom

Tom, I hate to be a pest or dense about this but I have moved my fixtures around. With the vented Lav closer to the toilet as shown, will I only just need the one vent off the Lav. Wouldn't the rest of the fixtures be wet vented with this arrangement?

Jerry

Jerry,
You're still discharging a major fixture past two unvented minor ones. Let me see what I can do.
Can you give me the measures between the walls?
How is the washer connected to the main? Regards, Tom

Jerry,
You're still discharging a major fixture past two unvented minor ones. Let me see what I can do.
Can you give me the measures between the walls?
How is the washer connected to the main? Regards, Tom


Tom, I added the dimensions, I haven't made any connectons yet so I can put the washer drain where ever I want. My job is still in the rough in stage. Just stud walls showing, so I can pretty much get in where I want to. The area where the drain exits the building is already determined and can't be changed and I think the latest drawing is where I want the fixtures.

Thanks, Jerry

Good morning Jerry,

If you wish to hold it down to one vent you'll have to keep all the fixtures on the same side of the main. I've drawn up a plan,(see image) that would use one vent and still stay in code. You may 45 the main over anywhere downstream of the fixture tie in point in plan "A". Notice I gave you a linen closet at the end of the room. I also gave you a plan "B". Let me know what you think. Cheers, Tom