DWV Riser Diagram Review for Basement Bathroom + Laundry

[MikeGA]

I'm hoping this is in the right section. I'm building a full 3 piece bathroom in the basement next to the existing laundry room and I mocked up a riser diagram. I'm hoping some experts can weigh in on my mockup and see what recommendations there are or what I need to change. I laid out 2 options.

Thanks in advance!

 

[MikeGA]

 

[Sponsor]

 

[wwhitney]

Your drawings are a bit confusing by trying to represent 3 dimensions all at once. Also it looks like in Option 2 you have a loop in the drain, near the shower WC. But a couple preliminary comments:

- NJ uses the NSPC which has some subtle differences from the IPC/UPC. So for a final answer you need to check the general guidance you're likely to get here against the specific provisions of the NSPC to be sure it's accurate.

- The 4" stack and 3" above it, that's carrying drainage down form the story above, presumably. What about the 2" vent shown above the lavatory at the right? Is that definitely a dedicated dry vent, carrying no drainage from the story above? If so, that's good, it takes care of your venting needs (tying all your dry vents back to it as shown). If not, you need a different venting strategy.

- Is the sink on the left a laundry sink? Generally the way to wet vent a WC and/or shower is with the lav drain. The laundry standpipe and laundry sink drain is kept separate from the bathroom fixtures, as they can't participate in the wet vent (unless the NSPC differs in this regard). And so the laundry sink would certainly need it's own vent takeoff as per Option 1 (the details there are unclear; the vent has to come off the laundry sink drain before it joins the standpipe drain or the trap arm turns downward).

- Why does the 2" drain on the left extend beyond the standpipe? Is something else draining in there?

- The shower and WC are not properly vented, because as mentioned you can't use the laundry fixtures to wet vent them.

Cheers, Wayne

 

[MikeGA]

Your drawings are a bit confusing by trying to represent 3 dimensions all at once. Also it looks like in Option 2 you have a loop in the drain, near the shower WC. But a couple preliminary comments:

- NJ uses the NSPC which has some subtle differences from the IPC/UPC. So for a final answer you need to check the general guidance you're likely to get here against the specific provisions of the NSPC to be sure it's accurate.

- The 4" stack and 3" above it, that's carrying drainage down form the story above, presumably. What about the 2" vent shown above the lavatory at the right? Is that definitely a dedicated dry vent, carrying no drainage from the story above? If so, that's good, it takes care of your venting needs (tying all your dry vents back to it as shown). If not, you need a different venting strategy.

- Is the sink on the left a laundry sink? Generally the way to wet vent a WC and/or shower is with the lav drain. The laundry standpipe and laundry sink drain is kept separate from the bathroom fixtures, as they can't participate in the wet vent (unless the NSPC differs in this regard). And so the laundry sink would certainly need it's own vent takeoff as per Option 1 (the details there are unclear; the vent has to come off the laundry sink drain before it joins the standpipe drain or the trap arm turns downward).

- Why does the 2" drain on the left extend beyond the standpipe? Is something else draining in there?

- The shower and WC are not properly vented, because as mentioned you can't use the laundry fixtures to wet vent them.

Cheers, Wayne

Thanks Wayne,

I'll answer each of your points.

Yes. The 2" vent shown above the lav is a dedicated vent that goes straight through the roof, no drainage there.
Yes. The sink on the left is a laundry sink. It's not shown properly, but its a 2" p-trap which then goes through the wall and ties into the 'regular' 2" drain. Based on your comment, I guess I would have to use option 1 with this because I tie directly into the dry vent.
No. The 2" drain doesnt extend beyond the standpipe...thats confusing.
For your last point...see option 3. This is venting the shower directly to the dry vent.

 

[wwhitney]

OK, I can't tell if you are using the correct fittings everywhere, because you don't specify the type of 90 degree elbow, and because the presentation of 3 dimensions all at once on a perspective view of the room makes it hard to tell horizontal from vertical.

But, given your previous response, you can use a connectivity pattern like the one shown below. The salient points:

The standpipe, laundry sink, lav, and shower all get dry vent takeoffs. Note that for the shower, the dry vent takeoff has to be vertical and stay vertical until 6" above the shower flood rim--no horizontal dry vents below the slab. Here "vertical" includes up to 45 degrees off plumb. The typical way to do that is to pass the shower drain under a wall, or bring it just alongside a wall.

Those dry vents can rise and combine and go to the existing 2" dry vent through the ceiling and ultimately roof. Where two or more dry vents connect, the connection has to be at least 6" above the flood rim of all the associated fixtures.

The WC is wet vented by the shower. For that, the WC fixture drain has to join the shower fixture drain before anything else comes in. "Fixture drain" means a drain carrying only one fixture, nothing else.

You can combine vented drains together however is convenient, e.g. the laundry fixtures could connect separately to the stack.

Cheers, Wayne

 

[MikeGA]

OK, I can't tell if you are using the correct fittings everywhere, because you don't specify the type of 90 degree elbow, and because the presentation of 3 dimensions all at once on a perspective view of the room makes it hard to tell horizontal from vertical.

But, given your previous response, you can use a connectivity pattern like the one shown below. The salient points:

The standpipe, laundry sink, lav, and shower all get dry vent takeoffs. Note that for the shower, the dry vent takeoff has to be vertical and stay vertical until 6" above the shower flood rim--no horizontal dry vents below the slab. Here "vertical" includes up to 45 degrees off plumb. The typical way to do that is to pass the shower drain under a wall, or bring it just alongside a wall.

Those dry vents can rise and combine and go to the existing 2" dry vent through the ceiling and ultimately roof. Where two or more dry vents connect, the connection has to be at least 6" above the flood rim of all the associated fixtures.

The WC is wet vented by the shower. For that, the WC fixture drain has to join the shower fixture drain before anything else comes in. "Fixture drain" means a drain carrying only one fixture, nothing else.

You can combine vented drains together however is convenient, e.g. the laundry fixtures could connect separately to the stack.

Cheers, Wayne

View attachment 83974

Is one way to accomplish the vent for shower by adding a Wye before the p trap and having the wye tie into the dry vent?

 

[wwhitney]

No, a vent has to connect to the fixture after the trap, and before the fixture drain has fallen more one pipe diameter from the trap outlet. The UPC also imposes a 5' length limit on a 2" trap arm; not sure about the NSPC.

If you want to use your lav drain to wet vent the shower and WC, that is possible. You'd need to route the lav drain over to hit the shower fixture drain, and then the WC fixture drain (or the NSPC may allow the opposite order; the IPC does, but the UPC does not). And the laundry drains would have to stay separate from this bathroom branch drain, as previously mentioned.

Cheers, Wayne

 

[MikeGA]

No, a vent has to connect to the fixture after the trap, and before the fixture drain has fallen more one pipe diameter from the trap outlet. The UPC also imposes a 5' length limit on a 2" trap arm; not sure about the NSPC.

If you want to use your lav drain to wet vent the shower and WC, that is possible. You'd need to route the lav drain over to hit the shower fixture drain, and then the WC fixture drain (or the NSPC may allow the opposite order; the IPC does, but the UPC does not). And the laundry drains would have to stay separate from this bathroom branch drain, as previously mentioned.

Cheers, Wayne

Sorry...but another question On your diagram, it shows a 4" wye branching to a 3" (to the left) and a 2" (to the right). Do they make such a wye?

 

[wwhitney]

Sorry...but another question On your diagram, it shows a 4" wye branching to a 3" (to the left) and a 2" (to the right).

Well, my markup of your diagram wasn't intended to indicate that level of detail, they could be stacked wyes with the branches at different levels. They could be two different branch that join horizontally and then have a single connection to the stack.

If you want to discuss that sort of question, please provide a scaled floor plan with the fixture locations and vertical pipes depicted as circles (their cross section).

Do they make such a wye?

If you needed such a thing you could get a 4x4x3x3 double wye and stick a 3x2 bushing into one of the 3" branch inlets.

Cheers, Wayne

 

[MikeGA]

Well, my markup of your diagram wasn't intended to indicate that level of detail, they could be stacked wyes with the branches at different levels. They could be two different branch that join horizontally and then have a single connection to the stack.

If you want to discuss that sort of question, please provide a scaled floor plan with the fixture locations and vertical pipes depicted as circles (their cross section).


If you needed such a thing you could get a 4x4x3x3 double wye and stick a 3x2 bushing into one of the 3" branch inlets.

Cheers, Wayne

Alright...I think I got it now. I've got all fixtures going directly to a dry vent. Will this work?

 

[wwhitney]

You can individually dry vent each fixture like that if you want.

The tricky part is that the WC and shower drains are below the slab, and the vents have to come off the horizontal drain rising at least 45 degrees above horizontal, and stay rising until at least 6" above the fixture flood rim. So if you can layout out your vent takeoffs to let your vents do that and get under a wall before rising above the slab, that's fine.

Cheers, Wayne