Venting help please...

[Pipe Dream]

Greetings! New construction, one bathroom on the ground floor with a shower, toilet, and sink, then a kitchen sink, dishwasher, and washer on the opposite wall. Can someone help or advise me on my main stack size? Can all drain vents be 1.5"? Thanks.

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[wwhitney]

Several details on your drawing aren't clear to me. But a few comments, based on the UPC, in use in WA state:

1) The vent for the WC, whether a direct dry vent, or via wet venting from the lav or shower, must be 2". All other dry vents can be 1.5". The total vent penetrations through the roof must be 3" in aggregate area, meaning (1) 3" vent, or (2) 2" vents plus (1) 1.5" vent, or (1) 2" vent plus (3) 1.5" vents. If this is an accessory building on a property that already has a main house whose venting complies with the aggregate area requirements, there is an allowance for reduced roof penetrations in the accessory building.

2) Dry vents can not be routed under the slab. To directly dry vent the WC would require running the WC fixture drain under (or almost under) a wall and take the 2" dry vent off vertically (which includes up to 45 degrees off plumb) up into the wall.

3) The only stack I see is the shown in the elevation for the washer and the kitchen. I'm unclear where that stack is located in the floor plan and how it connects to the under slab piping.

4) If you wish to use wet venting in the bathroom for the WC or the shower, then the dry vented lav or shower must connect to the fixture drain to be wet vented before any non-bathroom fixtures join the drain.

5) Any 2" trap (shower, washer standpipe) needs to be vented within 60" of horizontal run (and maximum 2" of fall) from the trap. It's unclear to me if your laundry standpipe trap outlet is within 60" of the stack.

6) If it is within 60" of the stack, then you can vertically wet vent the kitchen sink over the laundry standpipe like that, but the drain pipe/wet vent between the san-tee for the kitchen sink and the san-tee for the laundry standpipe would need to be 3". I.e. you could use a 3 x 1.5 x 1.5 san-tee for the kitchen sink, a 3" stack for the drainage portion, and a 3x3x2 san-tee for the laundry standpipe.

7) If it's not within 60" of the stack, or if you wish to avoid a 3" stack, you can take a 1.5" dry vent off the laundry trap arm and the kitchen sink trap arm separately, and once those vent takeoffs rise to at least 6" above both fixture flood rims, they could turn horizontal and then combine into a single 1.5" dry vent.

Cheers, Wayne

 

[Sponsor]

 

[Jeff H Young]

Evedently you have 5 differant posts regarding the project or it might be 4 but anway I answered some of your questions on another post maybe delete the others ?

 

[Pipe Dream]

Evedently you have 5 differant posts regarding the project or it might be 4 but anway I answered some of your questions on another post maybe delete the others ?

Hi Jeff, There's only 2 threads, this one and the other one you responded to. My apologies for not responding to you yet, I'm a busy dad and building a house for my family solo, so life is pretty full. I thought to pull the other thread, but it's a bit broader so I thought to leave it in case anyone else wishes to comment. I posted this thread as I thought maybe the other was too broad, and the venting is the place I need the most help with. I may decide to hire it out. Thanks.

 

[Pipe Dream]

Several details on your drawing aren't clear to me. But a few comments, based on the UPC, in use in WA state:

1) The vent for the WC, whether a direct dry vent, or via wet venting from the lav or shower, must be 2". All other dry vents can be 1.5". The total vent penetrations through the roof must be 3" in aggregate area, meaning (1) 3" vent, or (2) 2" vents plus (1) 1.5" vent, or (1) 2" vent plus (3) 1.5" vents. If this is an accessory building on a property that already has a main house whose venting complies with the aggregate area requirements, there is an allowance for reduced roof penetrations in the accessory building.

2) Dry vents can not be routed under the slab. To directly dry vent the WC would require running the WC fixture drain under (or almost under) a wall and take the 2" dry vent off vertically (which includes up to 45 degrees off plumb) up into the wall.

3) The only stack I see is the shown in the elevation for the washer and the kitchen. I'm unclear where that stack is located in the floor plan and how it connects to the under slab piping.

4) If you wish to use wet venting in the bathroom for the WC or the shower, then the dry vented lav or shower must connect to the fixture drain to be wet vented before any non-bathroom fixtures join the drain.

5) Any 2" trap (shower, washer standpipe) needs to be vented within 60" of horizontal run (and maximum 2" of fall) from the trap. It's unclear to me if your laundry standpipe trap outlet is within 60" of the stack.

6) If it is within 60" of the stack, then you can vertically wet vent the kitchen sink over the laundry standpipe like that, but the drain pipe/wet vent between the san-tee for the kitchen sink and the san-tee for the laundry standpipe would need to be 3". I.e. you could use a 3 x 1.5 x 1.5 san-tee for the kitchen sink, a 3" stack for the drainage portion, and a 3x3x2 san-tee for the laundry standpipe.

7) If it's not within 60" of the stack, or if you wish to avoid a 3" stack, you can take a 1.5" dry vent off the laundry trap arm and the kitchen sink trap arm separately, and once those vent takeoffs rise to at least 6" above both fixture flood rims, they could turn horizontal and then combine into a single 1.5" dry vent.

Cheers, Wayne

Thanks Wayne,

Responding to #3 I do not have the venting stack drawn in yet, as I wasn't clear about how it needed to be routed, mostly based on needing to establish the routes and sizes of the vents coming from the individual fixtures.

Regarding #5, I thought that a 2" pipe gave me a distance of 8' from a vent?

I'm gonna need to study #6.

#7 was one direction I have been strongly considering taking. I feel right on the fence as to whether I can do this myself. I know if I knew the course to take I could do it no problem, but there's so much to consider with venting, especially involving a washer placed how it is. I keep reading, watching good videos, and talking with people like yourself.

Thank you again,

Peter.

 

[wwhitney]

Regarding #5, I thought that a 2" pipe gave me a distance of 8' from a vent?

That the IPC. For the UPC, you are limited to 60".

Cheers, Wayne

 

[Pipe Dream]

I decided to have the plumber who did the slab work to do the venting and the rough in for the fixtures. I can do the rest.

 

[Jeff H Young]

wayne has made substantual comments I hope he was aware that the ground work is complete and slab is complete. because I wasent . so im confident you can get a good working system but you gotta be carful to meet code and depending how sharp inspector is could be few issues .
Didnt realize you had a plumber but some what I saw wasent right