Bathroom Venting Questions

[HereInOhio]

The upstairs to this house is being remodeled, adding a master bathroom in addition to redoing the layout of the current bathroom. Everything is removed (drywall, subfloor, hvac, plumbing, electrical), it is just the joist and studs currently. There is access above this bathroom with an open attic for any venting needed. I came looking for a recommendation of how to run the drains and vents.

The green line is the direction and rough location (first joist bay) where we would like the main dwv to run, the green circle is the stack in the basement that runs down a wall on the first level. I have to be careful of pipes going across the bays in the floor since HVAC supply and returns will run through the bay's I have marked with the red checkered. I do have an option to drop all the way down to the basement (large tub) or in this bathroom's walls (small vanity) to tie them in to make it work.

Any help would be greatly appreciated!

 

[Jeff H Young]

more detail if possible , use wyes to branch off for w/c 's the lav will be vent for shower and w/c

 

[Sponsor]

 

[HereInOhio]

more detail if possible , use wyes to branch off for w/c 's the lav will be vent for shower and w/c

I'm normally long winded so I was trying to keep it concise. I'm in Ohio so it's IPC. There is no plumbing currently so I was going to run it in PVC / PEX. The floor joist are 2x8's. This is an upstairs bathroom, with a bathroom/laundry room on the first floor below and then it exits through the floor of the basement. The orange sections are non load bearing dividing walls, the one that separates both bathrooms is 8" to run the HVAC up so I have plenty of room in that wall (vents can easily come down here and connect to the drains without having to run horizontal). Also since the HVAC goes up that wall the red checker to the right of the wall is incorrect, those joist bays will be open (below the small bathroom). There is a wall/cavity on the first floor that runs the same direction as the orange walls, it is where the stack comes up from (green circle). I could give a lot more info but I'm not sure if there's something specific you wanted details on?

My thought was to have the larger tubs drain drop down into the basement and be on it's own vent so I could leave the bays open where the HVAC is going. I figured I could drop the smaller vanity drain down into the same bay and connect with this tub drain -OR- run it in the floor over to vent at least one bathroom group.

As far as wet venting more than one bathroom group does that just mean I need two separate vents per group or does it mean I need to run two separate vents AND separate dwv's to each group? Assuming the later since the toilet needs to be first in the group from what I remember. It seems like there's lots of options (WC's completely separate since they are within 6', separate bathroom groups, separate tub/vanity and keep the rest together, ect) so I didn't want to start throwing out there what I was thinking. I assumed it didn't matter if you have way that is more efficient.

 

[HereInOhio]

Edited the above response to include this....

 

[HereInOhio]

Updated the drawing to correct the area blocked out for HVAC. I added how I was thinking about laying it out but please don't let it impact your suggestions, it's an open canvas right now. I also added the pink which is where I thought the vents would go.

In the 40" lav and shower I would only have one vent despite showing 2, either in the 8" wall (preferred) or behind the lav depending on which you guys think is better. I could run the lav dwv next to the shower and tie in after the vent or even vent both if needed.

I'm also trying to see if we could switch the bathtub drain to the other side, seems like it would make it a lot easier. I drew it assuming I could.

 

[wwhitney]

Every trap needs a vent at the elevation of the trap. So each lav will need a vent in the immediate vicinity. That would typically be a vent in the wall behind it, although it could be an AAV in the cabinet underneath the lav.

The right hand lav could wet vent the shower, tub, and both WCs (under the IPC). Or you can run dry vents in the middle wall as shown. For the shower and tub, the trap arms (from trap to vent) are limited to 6' in run and 1-1/2" in fall for a 1-1/2" trap; and 8' in run and 2" in fall for a 2" trap.

Cheers, Wayne

 

[Jeff H Young]

That's a general Idea I had then on the lav waste for bathroom on left use a 2 inch trap arm to the tub

 

[HereInOhio]

Every trap needs a vent at the elevation of the trap. So each lav will need a vent in the immediate vicinity. That would typically be a vent in the wall behind it, although it could be an AAV in the cabinet underneath the lav.

The right hand lav could wet vent the shower, tub, and both WCs (under the IPC). Or you can run dry vents in the middle wall as shown. For the shower and tub, the trap arms (from trap to vent) are limited to 6' in run and 1-1/2" in fall for a 1-1/2" trap; and 8' in run and 2" in fall for a 2" trap.

Cheers, Wayne

Thank you! I didn't realize you could wet vent more than one wc with a lav, I thought that made it more than a bathroom group.

Either way if you can, would this layout work?

For the lav on the right would I need a 2" dwv to wet vent the shower even though it's less than 6' from the dry vent or could I run the shower and lav dwv all in 1 1/2"? The lav on the left has a dry vent for itself and ties into the stack, is 1 1/2" dwv ok considering the WC's will flow past it going into the same stack? Lastly, for the dry vent's is 1 1/2" sufficient or do I need 2"?

 

[wwhitney]

All the vents, and the drains just carrying one lav, can be 1-1/2" under the IPC.

For maximum wet venting, you could delete both vents in the 8" wall. The righthand lav could wet vent everything other than the left hand lav. But the dry vents in the 8" wall are fine to have.

The upper (on the page) 8" wall dry vent might be better placed on the WC fixture drain before it joins the lav/tub/shower, as that actually makes it the dry vent for that WC. Otherwise, it's just an optional relief vent, as the WC is being wet vented by the lav. Not sure if it really makes a difference.

A shower drain is best done in 2" anyway, so use a 2" shower trap and drain. Running the lav drain perpendicular to the joists might be cleaner. The tub trap and drain can be 1-1/2", unless you need to go to 2" because you don't dry vent the tub and the distance to the shower/lav drain exceeds 6' of run / 1-1/2" of fall.

One option that would involve drilling the joists only once instead of twice would be: Omit the tub dry vent. Run the right hand lav drain towards the tub and let that lav wet vent the tub. Then either: (a) have the tub/lav drain hit the shower (only), then the WC, for the lav to wet vent both of them or (b) put the upper (on the page) dry vent on the shower trap arm only, then have that hit the WC to wet vent it, then join the lav/tub to that.

Cheers, Wayne

 

[HereInOhio]

The upper (on the page) 8" wall dry vent might be better placed on the WC fixture drain before it joins the lav/tub/shower, as that actually makes it the dry vent for that WC. Otherwise, it's just an optional relief vent, as the WC is being wet vented by the lav. Not sure if it really makes a difference.

I moved it, I think this is what you explained? If I do it this way would a double wye be okay for the WC (as pictured) or would you recommend having two single wye's join at different places?

One option that would involve drilling the joists only once instead of twice would be: Omit the tub dry vent. Run the right hand lav drain towards the tub and let that lav wet vent the tub. Then either: (a) have the tub/lav drain hit the shower (only), then the WC, for the lav to wet vent both of them or (b) put the upper (on the page) dry vent on the shower trap arm only, then have that hit the WC to wet vent it, then join the lav/tub to that.

Good Idea, I originally was thinking that but was picturing a tee with the water coming from both directions, this would make that idea work. I could always just run dry vents up from both of the green pipes where it hits the 8" wall then tie them all together above the flood line if it would be beneficial? Is 3" fine for the green or do I need to go up to 4"? When tying the 2" shower to the 3" WC (or 4" depending on previous question) can I use a reducer bushing or do I need an eccentric fitting?

 

[wwhitney]

As to your latest picture, I'm unclear where the toilet flanges are, perhaps you could draw them in as circles. Those circles should be 12" off the finish wall behind the WC. And so depending on how far off the top (on the page) wall the drain stack on the left is, that will influence which joist bays you run the left-right (on the page) horizontal drains in.

But I think you have the vent in the 8" wall on the combined tub/lav/shower, rather than on the WC fixture drain, which is what I suggested.

As to the double wye, separate wyes are a better choice so you can adjust the slope of the branch inlets independently. Plus it might be hard to fit a double wye in a joist bay.

3" is fine for all the green, and reducer bushings (or reducing fittings) are also fine, no need for anything eccentric. Also, it is correct as drawn that if the lav/tub/shower is going to wet vent either WC, then the 3" needs to start at the wye/combo where the lav/tub joins the shower. So that should end up a 3x2x2 fitting, and the lav/tub joint should be a 2x1-1/2x1-1/2 fitting (or either of the inlets could be 2" if preferred).

Maybe someone else with more hands-on experience will comment on the various options you have now, in case there are any factors I'm overlooking.

Cheers, Wayne

 

[HereInOhio]

As to your latest picture, I'm unclear where the toilet flanges are, perhaps you could draw them in as circles. Those circles should be 12" off the finish wall behind the WC. And so depending on how far off the top (on the page) wall the drain stack on the left is, that will influence which joist bays you run the left-right (on the page) horizontal drains in.

Correct, the WC on the right will be 12" off the finished wall. The one to the left will be approx. 15" off the finished wall.

But I think you have the vent in the 8" wall on the combined tub/lav/shower, rather than on the WC fixture drain, which is what I suggested.

I apologize, I'm not exactly sure I understand since there is no way I see to get the vent downstream of the WC on the left. I could tie in the WC on the right upstream of the vent but it would only be that WC and not both....Is this way what you were explaining?

 

[Jeff H Young]

OK I see you swapped the drain sides on the tub . that works or you could have came off the other lav for the tub if you wanted drain and valve on other end of tub

 

[wwhitney]

I apologize, I'm not exactly sure I understand since there is no way I see to get the vent downstream of the WC on the left. I could tie in the WC on the right upstream of the vent but it would only be that WC and not both....Is this way what you were explaining?

First, you can delete the vent in the 8" wall, and everything is still properly vented. Each lav is dry vented, and the right hand lav wet vents the tub, the shower, WC 1 (right), and then WC 2 (left).

Now if you have an extra dry vent in the location you show, it's just a bonus relief vent. WC1 is still wet vented by the lav, as the WC1 drain hits the lav drain before it hits that vent. Maybe the dry vent is still useful that way, I don't know.

But if you want to dry vent WC1, then you put the vent like in the drawing below, which is what I was trying to explain. WC2 is still wet vented by the lav/WC1. With WC1 dry vented, you could alternately join WC1 to WC2 before they both join the lav/shower/tub; then WC2 is wet vented by WC1, and the lav/shower/tub drain is not doing any further wet venting, and doesn't need to be upsized to 3" before hitting the WCs.

One more important point is the exact location of the two joists closest to the top-of-page wall (finish surface). You have WC1 at 12" off that wall, and WC2 at 15"+; I don't think you've specified where the drain stack is relative that wall. Best case is that all three of those locations (WC1, WC2, and the drain stack) are within the same joist bay; that way none of your 3" drains should go through any joists.

And so you want to design around the joist locations to minimize 3" drains going through joists. If your joist is solid sawn 2x10 or smaller, you can't prescriptively drill the joist for a 3" drain, and you'll need some pre-engineered reinforcement for any hole you make. If they are solid sawn 2x12s, or I joists (generally, see manufacturer's literature), you have more flexibility on drilling them.

Cheers, Wayne

 

[Jeff H Young]

Good you noticed w/c locations Wayne that's a huge space between wall and the tub approx 48 inches and no one likes a w/c 15 inches off side wall 15 inches on one side and 33 on the other side of w/c
The HVAC in basement I guess means that toilet needs to be where it shows? I'm thinking it might be better in next joist bay but guessing

 

[HereInOhio]

good you noticed w/c locations Wayne that's a huge space between wall and the tub approx 48 inches and no one likes a w/c 15 inches off side wall 15 inches on one side and 33 on the other side of w/c
The HVAC in basement I guess means that toilet needs to be where it shows? I'm thinking it might be better in next joist bay but guessing

It’s a friends house I’m trying to help out. I did say something about 15” being the minimum and he should give even a few more inches but it seemed like he wanted to leave it. I’ll mention the pros suggestions and see what he thinks.

The stack is the circle at the end of the green. The original picture had it listed but yes they are all in the same bay. 21” between those two joist…..I said ummm what about 16” and the reply I got back was “it was 24”).

Thanks everyone for the help. I’ll probably need to bother you again about plumbing the first floor bathroom but think I may have that covered.

 

[HereInOhio]

I’m working on this now and ran into a quick question. I know normally if you are transitioning from a horizontal drain to vertical you need to use a san tee and not a wye because the weir could potentially be blocked. In the case of the lav to the left in my picture I have a 2” dry vent coming in the top and that is the only thing draining into the 4” from that pipe. Above on the 4” stack the upstairs bathroom would come into the 4” but that is vented elsewhere.

Would it be acceptable for me to use a wye? Seems to me it would flow better opposed to using a San tee and a 90 coming off the 4” especially since I don’t have room for a LT 90.

 

[wwhitney]

I’m working on this now and ran into a quick question. I know normally if you are transitioning from a horizontal drain to vertical you need to use a san tee and not a wye because the weir could potentially be blocked.

Did not read the rest of your question, but the above is true only when the drain horizontal to vertical transition is taking place at the same place the dry vent is coming off. For a vented drain, a wye is fine and perhaps preferred.

I.e. the restriction is about venting, not about general drain behavior.

Cheers, Wayne

 

[Jeff H Young]

Santee is required if its a trap arm but in case of a lav branching off of a vertical stack and its just a drain for the lav and not the trap arm a santee is optional or a wye type fitting santee is fine and often preferred for fitting in tighter spaces plus cheaper than a combi or a wye and 45, and drains well in this type application