Best way to attach and vent upstairs plumbing?

[Rocketman69]

I'm hoping you guys can set me in the right direction here. I'm renovating an apartment that's attached to my workshop for my mother in law. Due to a miscommunication between me, my old plumber, and my old carpenter; the waste stack ended up on an exterior wall below the staircase.

I need to attach the upstairs bathroom group, a laundry, and a kitchen sink/dishwasher to this stack, but I'm unsure of the best way to tie in, and properly vent everything.

I'm able to continue the 3" up the wall next to the stairs and vent through the roof, but all of the upstairs DWV plumbing will be on the other side of the staircase opening.

The main waste stack is in line with the joist bay that will be below the kitchen sink (albeit ~22 feet across the building), and the shower drain & closet flange will be in the two joist bays on either side of that one.

Bathroom sink and laundry will have to travel across joist bays to tie in with the others.

My idea was to wye into the main stack across the bottom of the stair stringers, and then up below the bathroom, but I'm kinda stuck there.

I've attached some photos to hopefully give a better idea of what I'm talking about. The plumbing in the pictures is just a partial mock-up I was making from spare pieces of pipe and fittings I had in the shop. Nothing is cemented.

 

[wwhitney]

We're going to need a floor plan that also shows which way the joists run.

Cheers, Wayne

 

[Sponsor]

 

[Rocketman69]

We're going to need a floor plan that also shows which way the joists run.

Cheers, Wayne

Wayne,

Thanks for the quick response. The joists run perpendicular to the staircase. I don't have the plans handy, but I've attached a couple more pictures. The first shot is from below the closet flange. In the SketchUp image, the joists would run from the top of the picture to the bottom.

Kitchen sink drain will have a straight shot from the east wall to the staircase within a single joist cavity.

 

[Terry]

The sewage ejector needs a shutoff valve so that it can be worked on, and it also needs a vent through the roof.

Vents can tie together at 6" above the highest flood level.

 

[wwhitney]

Extending the 3" line between the stairs and the exterior wall as a vent is not so useful. Anything that drains into that segment you show crossing underneath the stairs will already need to be vented. So between the exterior wall and the stairs is the wrong place for a vent.

Can you put a 3" vertical segment on the other side of the stairs, in the wall between the stairs and the toilet? And then extend that through the roof as your vent?

Cheers, Wayne

 

[Rocketman69]

The sewage ejector needs a shutoff valve so that it can be worked on, and it also needs a vent through the roof.

Vents can tie together at 6" above the highest flood level.

Terry,

The crock in the picture is just a sump pump, not connected to the waste system in any way.

Extending the 3" line between the stairs and the exterior wall as a vent is not so useful. Anything that drains into that segment you show crossing underneath the stairs will already need to be vented. So between the exterior wall and the stairs is the wrong place for a vent.

Can you put a 3" vertical segment on the other side of the stairs, in the wall between the stairs and the toilet? And then extend that through the roof as your vent?

Cheers, Wayne

Wayne,

I was under the impression that the 3" main stack should always continue vertically through the roof. Unfortunately, the back (North) wall of the bathroom sits directly above the double joists of the stairway opening, so I cannot run straight up through the floor into that wall.

My thought was that I could run a 2" vent for shower and w/c up into the east bathroom wall, then maybe turn into the north bathroom wall from there until it can go straight up and across the stairway opening within the ceiling joist cavity in line with the stack vent, tying in there. But maybe that would complicate things too much. Not sure how advisable it is to have a lot of turns in the horizontal section of a branch vent.

 

[wwhitney]

I was under the impression that the 3" main stack should always continue vertically through the roof.

You always need "enough" vent going through the roof, but it doesn't have to be a single multi-story vertical pipe segment. You can offset the "stack" by 4' horizontally under the stairs.

As to how much is "enough," which plumbing code are you under? If it's the UPC, you'll need at least a 3" vent (or an equivalent area, e.g. two 2" vents and a 1-1/2" vent). I think the IPC may require less.

Unfortunately, the back (North) wall of the bathroom sits directly above the double joists of the stairway opening, so I cannot run straight up through the floor into that wall.

Depending on your bathroom design, it might be worth jogging around the double joist with a pair of 45s, that would just make an incursion into your bathroom space which you'd have to box out or hide in a vanity or something. But there are other options.

For example you may be able to put the main vent in the east wall of the bathroom. Since you don't need the 3" vertical segment between the stairs and the exterior wall, you wouldn't need to jog that vent back to that location, it can just go straight up.

Cheers, Wayne

 

[Rocketman69]

You always need "enough" vent going through the roof, but it doesn't have to be a single multi-story vertical pipe segment. You can offset the "stack" by 4' horizontally under the stairs.

I should also mention that there is a half bath and laundry in the lower level that are tied into that stack below the slab.

As to how much is "enough," which plumbing code are you under? If it's the UPC, you'll need at least a 3" vent (or an equivalent area, e.g. two 2" vents and a 1-1/2" vent). I think the IPC may require less.

I'm in Kansas City, MO; so I believe we're under UPC on this side of the border.

Depending on your bathroom design, it might be worth jogging around the double joist with a pair of 45s, that would just make an incursion into your bathroom space which you'd have to box out or hide in a vanity or something. But there are other options.

I'd rather not have to try and hide the incursion. If it came down to that, I'd just move the bathroom walls..... Not that I'm interested in doing that either.

For example you may be able to put the main vent in the east wall of the bathroom. Since you don't need the 3" vertical segment between the stairs and the exterior wall, you wouldn't need to jog that vent back to that location, it can just go straight up.

Cheers, Wayne

This might be a better option. The downstairs toilet has to be went vented via the sink, so I assume I could just come up with the 2" for the downstairs lav vent into the floor joist cavity below that east wall, and tie into the vent above the upstairs flood level.

I'm still going to have to figure out a way to vent the upstairs laundry and bathroom sink though. I assumed the kitchen sink would need it's own vent thru the roof anyway, due to the distance. I had just hoped to be able to get the rest of the place vented with only one additional hole in the roof.

 

[wwhitney]

Having a little trouble keeping all the fixtures straight, so floor plans with all the fixtures and all the piping runs installed already would be very helpful.

If you have a wide open attic, you can combine all the vents into a single 3" roof penetration. Or if it would be easier, you can keep separate roof penetrations, and if you go with (3) penetrations, you don't need any 3" penetrations, it would be enough to have (2) 2" penetrations and an 1-1/2" penetration.

Cheers, Wayne

 

[Rocketman69]

Having a little trouble keeping all the fixtures straight, so floor plans with all the fixtures and all the piping runs installed already would be very helpful.

I threw a quick sketch together that hopefully clears things up a bit. The note in the downstairs portion of the sketch that says " 2" for laundry " is referring to the downstairs laundry.

If you have a wide open attic, you can combine all the vents into a single 3" roof penetration.

Unfortunately, there is no access to the attic....or perhaps more prudent to say they're isn't one. The building used to have a flat roof, and the original owners built a shingled hip-roof on top of that. Ceiling joists are 16" on center, and there's no attic access built into it.

Or if it would be easier, you can keep separate roof penetrations, and if you go with (3) penetrations, you don't need any 3" penetrations, it would be enough to have (2) 2" penetrations and an 1-1/2" penetration.

Cheers, Wayne

If decide to go that route, which fixtures would I be connecting to each vent stack?

 

[wwhitney]

I threw a quick sketch together that hopefully clears things up a bit. The note in the downstairs portion of the sketch that says " 2" for laundry " is referring to the downstairs laundry.

Thanks, that will allow me or someone else to advise you better. How are the floor drains vented?

Unfortunately, there is no access to the attic....or perhaps more prudent to say they're isn't one. The building used to have a flat roof, and the original owners built a shingled hip-roof on top of that. Ceiling joists are 16" on center, and there's no attic access built into it.

If there is an enclosed attic, but no access, then it typically wouldn't be hard to cut one ceiling joist for a 32" wide attic access. Or you could possibly run the vents just within the ceiling joists, depending on the joist size and the distances involved.

If decide to go that route, which fixtures would I be connecting to each vent stack?

Off the top of my head, I'd say a 1-1/2" for the kitchen, a 2" for the downstairs toilet and lav, and a 2" for everything else. [Need to double check 2" is enough for "everything else", but I expect so.]

Or if you can get all the vents lined up left right on your drawing within the walls/first floor joists, then they could all enter the same ceiling joist bay and connect up in the middle to a single 3" roof penetration.

Cheers, Wayne

 

[Rocketman69]

Thanks, that will allow me or someone else to advise you better. How are the floor drains vented?

You know.... That's a damned good question. I didn't plumb the stuff below the floor. I guess I took for granted that part was done properly.

If there is an enclosed attic, but no access, then it typically wouldn't be hard to cut one ceiling joist for a 32" wide attic access. Or you could possibly run the vents just within the ceiling joists, depending on the joist size and the distances involved.

I had considered making an access hole, but I'm concerned that the distance between the peak of the hip roof and the old flat roof might not be enough to work with anyway.

Off the top of my head, I'd say a 1-1/2" for the kitchen, a 2" for the downstairs toilet and lav, and a 2" for everything else. [Need to double check 2" is enough for "everything else", but I expect so.]

Or if you can get all the vents lined up left right on your drawing within the walls/first floor joists, then they could all enter the same ceiling joist bay and connect up in the middle to a single 3" roof penetration.

Cheers, Wayne

Apparently, a 2" vent can serve 24 f.u., so even if I ran everything to one vent, I think I'd be covered, as I think my worst case scenario is 22 f.u. The kitchen group is going to need it's own vent, just due to location. I can't imagine trying to tie that vent all the way back to the north wall with no walls in line.

After our earlier interaction, I tried about two dozen combinations, attempting to figure out a way to properly vent the toilet/shower. Nothing seemed like it was working.

Then I realized that the north wall of the bathroom sitting on the double joist was screwing me over when it came to my supply lines as well. So.....I moved the whole bathroom 3½" south. I think this will simplfy things.

 

[Rocketman69]

Ok.... Just a follow up on my previous post:

I moved the bathroom walls and can now run 2" vents for the WC & Shower up through the north wall into the ceiling.

I'm trying to figure out the best way to tie in the kitchen sink, shower, and WC to the stack. Can someone take a look at the attached sketch and see if this seems like the right approach? Sketch is drawn looking south from stairway toward kitchen area.

 

[Reach4]

Shower venting is not right. Can you make the transition from horizontal to vertical with a sanitary tee (santee)? That is not the only good way, but it is often the easiest.

The shower trap arm needs to stay horizontal until the vent.

 

[Rocketman69]

Thanks for the quick response. I thought that might be the case. Probably should have known better. I'm trying to work around tight tolerances between three joist bays, and thought it might work.

How about the updated sketch?

 

[wwhitney]

If the kitchen sink drain is already vented, then your vent takeoffs for the shower and toilet are good, and the way you tie the drains together is good.

The rightmost wye could be a 3x3x2 wye, with everything to the left 2". Where does the lav come in?

Cheers, Wayne

 

[Reach4]

I had not been following this thread. Looking back at post #10, you had a sketch that shows the lavatory waste joining the WC waste. If that is the WC referred to in your later pictures, likely no further venting of that WC is needed.

 

[Rocketman69]

If the kitchen sink drain is already vented, then your vent takeoffs for the shower and toilet are good, and the way you tie the drains together is good.

Thanks for the confirmation. I'm going to vent the kitchen sink straight up at the outside wall where that sink is located, since it is around 20' from the main stack.

The rightmost wye could be a 3x3x2 wye, with everything to the left 2". Where does the lav come in?

My original plan was to come across with the upstairs Washer & lav drains, and tie in to the kitchen sink lateral on its way to the stack, but due to the layout of the laundry closet walls, it seems I might have to run the laundry drain straight back through the rear closet wall to the north exterior wall, long sweep 90 around a corner then straight to the original 3" stack (the portion that comes straight up between the north exterior wall & staircase). As for the lav, I'm wondering which would be the best route: 1) across the joist cavities to the kitchen sink drain line, 2) 90 just past the WC running parallel until they both get to the stack, or 3) tie into WC drain and wet vent the WC via the lav.

I had not been following this thread. Looking back at post #10, you had a sketch that shows the lavatory waste joining the WC waste. If that is the WC referred to in your later pictures, likely no further venting of that WC is needed.

You might be referring to the sketch of the lower floor plumbing layout, although I suppose I could wet vent the upstairs WC via the upstairs lav as well.

 

[wwhitney]

My original plan was to come across with the upstairs Washer & lav drains, and tie in to the kitchen sink lateral on its way to the stack, but due to the layout of the laundry closet walls, it seems I might have to run the laundry drain straight back through the rear closet wall to the north exterior wall, long sweep 90 around a corner then straight to the original 3" stack (the portion that comes straight up between the north exterior wall & staircase).

How's that?

I would think just put your laundry box in the wall between the alcove and the bath lav, then you can combine the vents higher up in that wall and combine the drains lower down or in the floor system. Likewise, I assume you are going to combine the shower and WC vents once you get 6" above the WC flood rim.

Are your joists 2x10s? If so, no problem drilling them at 2-1/2" or 2-3/4" for a 2" drain line, just keep your holes 2" clear from the top and bottom of the joist.

Cheers, Wayne

 

[Rocketman69]

How's that?

I would think just put your laundry box in the wall between the alcove and the bath lav, then you can combine the vents higher up in that wall and combine the drains lower down or in the floor system. Likewise, I assume you are going to combine the shower and WC vents once you get 6" above the WC flood rim.

I suppose I could put the washer box in the shared wall with the lav. Didn't really think about having the standpipe next to, instead of behind, the washer. Can the shower and WC vents tie in at 6" above the WC flood rim? I assumed it was 6" above the flood rim of the highest fixture.

Are your joists 2x10s? If so, no problem drilling them at 2-1/2" or 2-3/4" for a 2" drain line, just keep your holes 2" clear from the top and bottom of the joist.

Yes, they are 2x10. I had intended to drill through for the lav, so I suppose a bigger hole for a shared laundry/lav drain wouldn't be much of an issue. Where to tie that 2" in to the rest of the system is the question though.