3" PVC DWV Wye and 45° Elbow Combo w/ 2" L Side Inlet

[DaveNewhampshire]

Hello ... see picture, hopefully it attached as this is my first post. I apologize if the picture is somewhat crude as I hastily put it together. I am rough plumbing a new bathroom over a garage, and I would like to stay inside the 16" wooden i-beam joist cavities versus having pipes inside the garage space. Can this fitting (3" PVC DWV Wye and 45° Elbow Combo w/ 2" L Side Inlet) be used in the horizontal plane, with the 2 inch side inlet straight up to connect a 2" dry vent pipe for the Water Closet? I am finding it difficult to keep the dry vents from going horizontal before it's 6 inches above flood plane, especially with limited vertical walls to work with. I am not sure if the vent inlet being straight versus 45 is an issue, although it will strictly be a dry vent with no drainage at all. I thought about using a 3-3-2 wye, but the extra clearance for the vent is a problem. Hopefully I am clear, and the picture comes through. FYI, I am in NH and we follow IPC. Thanks in advance for any advise ... this forum is a great resource!

 

[wwhitney]

Not 100% sure of the answer to your question, but I will say that if the fitting shown can be used for drainage at all, the way you propose to use it would be basically the only allowable way to use it.

If you want a similar solution with more standard fittings, then you could instead use (going upstream) a wye, a street san-tee on its back, and a street 45. The IPC allows a san-tee on its back for venting.

Of course, that would not be as compact as the fitting you show. And since the IPC allows a san-tee on its back for venting, I don't see why your proposal wouldn't be allowed.

Cheers, Wayne

 

[Sponsor]

 

[DaveNewhampshire]

Not 100% sure of the answer to your question, but I will say that if the fitting shown can be used for drainage at all, the way you propose to use it would be basically the only allowable way to use it.

If you want a similar solution with more standard fittings, then you could instead use (going upstream) a wye, a street san-tee on its back, and a street 45. The IPC allows a san-tee on its back for venting.

Of course, that would not be as compact as the fitting you show. And since the IPC allows a san-tee on its back for venting, I don't see why your proposal wouldn't be allowed.

Cheers, Wayne

Thanks Wayne! That was going to be my follow up question ... what else can a side inlet be used for, other than a dry vent? I thought about a sanitary tee on its back for a 2" vent going vertical, and essentially it would be doing the same thing as the fitting I asked about, although I guess the San-tee has a little bit of directional curve, but the combo fitting with side inlet gives me the horizontal curve i need as well. Not sure if a directional curve is necessary with a dry vent, other than rain or condensation draining back down.
As a DIY'er, I am having trouble figuring out venting options while trying to stay in the joist cavity without using horizontal vent runs (which I know are not allowed per IPC unless 6" above flood rim). I know wet venting is an option under IPC, and I do have a double lav feeding into the main horizontal run between the WC and the stack further down the line, so I may have to go that route if my set up won't pass inspection. I would like to have a dry vent for the WC if possible. Thanks again!

 

[wwhitney]

With 16" I joists it shouldn't be hard to dry vent the WC. How about a drawing showing the I-joist locations, the WC location, walls above that the vent can enter, and where the drain needs to end up? Or the same for the whole bathroom if you like.

Cheers, Wayne

 

[DaveNewhampshire]

With 16" I joists it shouldn't be hard to dry vent the WC. How about a drawing showing the I-joist locations, the WC location, walls above that the vent can enter, and where the drain needs to end up? Or the same for the whole bathroom if you like.

Cheers, Wayne

I do have some drawings to show the building inspector when I go to pull the permit, so I will try to figure out how to put the drain/vent paths in them and post it on this thread. Although my garage joists are 16" deep, where I tie into the main house leading to the basement is only a few inches down from the top of the garage subfloor, so I need to stay pretty close to the subfloor to keep my minimum slope, and the WC is a good 8 feet or so from the tie in and one joist bay over. Thus the limited options to dry vent the WC with a wye, even if the vent was at 45 degrees. All drains are horizontal until i hit the tie in at the main house, and then I will run a 3" stack down to the basement and tie into the existing drain. I will run a separate vent through the roof of the garage. Once again thank you for the feedback, and I will try to post some pics tomorrow.

 

[John Gayewski]

In UPC world that fitting isn't allowed in drainage. The side inlet isn't a drainage pattern and your below the flood rim.

 

[John Gayewski]

Od

I do have some drawings to show the building inspector when I go to pull the permit, so I will try to figure out how to put the drain/vent paths in them and post it on this thread. Although my garage joists are 16" deep, where I tie into the main house leading to the basement is only a few inches down from the top of the garage subfloor, so I need to stay pretty close to the subfloor to keep my minimum slope, and the WC is a good 8 feet or so from the tie in and one joist bay over. Thus the limited options to dry vent the WC with a wye, even if the vent was at 45 degrees. All drains are horizontal until i hit the tie in at the main house, and then I will run a 3" stack down to the basement and tie into the existing drain. I will run a separate vent through the roof of the garage. Once again thank you for the feedback, and I will try to post some pics tomorrow.

If you can't stay vertical below the flood rim you don't have to. Provide a cleanout for the vent. But generally there's a way.

 

[Jeff H Young]

If Davenewhash sees a way of horizontal wet venting off lavs I'd like that better than this fitting . just a matter of the vent remaining clear a santee on back I would prefer over that special combi as well

 

[wwhitney]

a santee on back I would prefer over that special combi as well

I'm curious, why's that?

Is it the lack of curvature on the combo side inlet? Would you say that the IPC disallows a vent-tee on its back as the vent takeoff, but allows a san-tee on its back?

Or is it just a matter of preferring to avoid more complicated patterns?

Cheers, Wayne

 

[DaveNewhampshire]

If Davenewhash sees a way of horizontal wet venting off lavs I'd like that better than this fitting . just a matter of the vent remaining clear a santee on back I would prefer over that special combi as well

I am still working on drawings, but I think this would meet IPC code for wet venting (see picture). We live in a small town, and the one building inspector does building/electrical/plumbing inspections, so even if technically legal to use that funky fitting with the side inlet (or San-tee on back), to dry vent the WC, I want to avoid the "I've never seen it done that way before, I need to check on that ..." from the inspector. I think the wet vent would be more straight forward. The one question is can the 2" drain/wet vent come in at a horizontal (less than 45 degrees) angle to the 3" drain in joist, because it's both a drain and a wet vent, or does it need to come in at 45 or greater like a dry vent? From a clearence standpoint, greater than 45 with a 3x3x2 wye and 45 street coupling may create height issues. A drawing would be clearer I am sure, but the WC is the furthest upstream, and is about 5 feet away from the lav/wet vent connection, and then another couple feet to the stack vertical connection.

This forum is a tremendous resource for guys like me who know just enough to get in trouble! Thanks in advance.

 

[wwhitney]

In horizontal wet venting, conventionally the wet vent is all horizontal (2% slope), with the exception of a vertical segment at the lav san-tee (or double fixture fitting in this case). So a dry vent at the lav can wet vent the shower and WC and could be the only vent for the bathroom group.

Cheers, Wayne

 

[DaveNewhampshire]

In horizontal wet venting, conventionally the wet vent is all horizontal (2% slope), with the exception of a vertical segment at the lav san-tee (or double fixture fitting in this case). So a dry vent at the lav can wet vent the shower and WC and could be the only vent for the bathroom group.

Cheers, Wayne

Thanks Wayne ... that is good news for my joist height issue (drain/wet vent connecting to main drain at normal slope horizontal). However, my free standing tub and seperate shower are located on the opposite side of the room, and although they eventually connect to the main vertical stack to the basement for draining, I was going to have seperate dry vents for each bath/shower fixture eventually connecting up in the attic before going through the roof. Did you mean the wet vent has to be the only vent for the bathroom group, or can I wet vent the WC/lavs together, and dry vent the other 2 seperately? Perhaps I misread that you meant I could use it for all fixtures if needed.
Also, is the 2" pipe between the double fixture and the 3" pipe in the joist sufficient capacity to drain 2 lavs and wet vent a WC simulaneously? Thanks

 

[wwhitney]

For the IPC/IRC, a 1-1/2"wet vent is good for 1 DFU of drainage; 2" is good for 4 DFU; and above that you need 3".

Yes, can = could.

You could dry vent the lav and have it wet vent the WC; and dry vent the tub and have it wet vent the shower (or vice versa).

Cheers, Wayne

 

[DaveNewhampshire]

For the IPC/IRC, a 1-1/2"wet vent is good for 1 DFU of drainage; 2" is good for 4 DFU; and above that you need 3".

Yes, can = could.

You could dry vent the lav and have it wet vent the WC; and dry vent the tub and have it wet vent the shower (or vice versa).

Cheers, Wayne

Sounds good Wayne, thanks! Sorry if I am beating a dead horse here, but this is the method I believe I will go with and just want to be 100% sure before I start cutting holes. Lav=1 dfu each (2 total), WC = 3 dfu, so the 4 dfu limit for 2" wet vent pipe is for drain only, correct? So I am draining 2 dfu's, and venting 3 dfu's through the wet vent portion, and venting 5 dfu's through the 2" dry vent. Does all that meet IPC code in your opinion? Also, the wall where the double fixture fitting is located is 2x6, so I could jump up to 3" dry vent at the top of the double fixture fitting versus closer to the ceiling if it matters. Thanks again, and I think that is all my questions (for now anyway). ;-)

 

[wwhitney]

Sounds good Wayne, thanks! Sorry if I am beating a dead horse here, but this is the method I believe I will go with and just want to be 100% sure before I start cutting holes. Lav=1 dfu each (2 total), WC = 3 dfu, so the 4 dfu limit for 2" wet vent pipe is for drain only, correct?

Yes, that's why I emphasized "DFU of drainage." A wet vent is sized by what is draining through it, not what it is venting. [It has to be at least as large as a dry vent for the downstream fixtures would have to be, but that typically doesn't control the sizing.]

As far as upsizing your vent for the roof penetration, that should happen ~12" before the vent exits the thermal envelope. I don't see any upside to doing it lower down.

Cheers, Wayne

 

[DaveNewhampshire]

Yes, that's why I emphasized "DFU of drainage." A wet vent is sized by what is draining through it, not what it is venting. [It has to be at least as large as a dry vent for the downstream fixtures would have to be, but that typically doesn't control the sizing.]

As far as upsizing your vent for the roof penetration, that should happen ~12" before the vent exits the thermal envelope. I don't see any upside to doing it lower down.

Cheers, Wayne

Once again, excellent information Wayne! I am going with this plan, and maybe before I start cementing things together I will take pics of the dry fit and post to make sure it looks ok. Cheers to you as well!

 

[wwhitney]

dry fit

Be aware that dry fitting plastic DWV does not permit full depth insertion as it is an interference fit enabled by the solvent cement. So either your fittings will move closer by 1/4" to 1" depending on size, or you'll have to recut longer pipe pieces.

Cheers, Wayne

 

[DaveNewhampshire]

Be aware that dry fitting plastic DWV does not permit full depth insertion as it is an interference fit enabled by the solvent cement. So either your fittings will move closer by 1/4" to 1" depending on size, or you'll have to recut longer pipe pieces.

Cheers, Wayne

Good point ... I will take that into account, or just go ahead and cement them together and then if I have to, cut them apart. Besides the double fixture fitting I had to order online, the rest of the fittings are easily available at Home Depot/Lowes, and not crazy expensive.

 

[wwhitney]

If you want feedback before cementing, you could spatially arrange the fittings in their relative positions and orientations, I can imagine the pipes. Or you could use very short sections for a dry fit mockup.

Cheers, Wayne

 

[Jeff H Young]

I'm curious, why's that?

Is it the lack of curvature on the combo side inlet? Would you say that the IPC disallows a vent-tee on its back as the vent takeoff, but allows a san-tee on its back?

Or is it just a matter of preferring to avoid more complicated patterns?

Cheers, Wayne

I prefer the flow of a santee on its back over the looks of the comb (it might be the view ) never seen the3 fitting up close I think IPC is ok with the santee on back. I was taught to use san tees on back and got away with it not knowing better that it was prohibited here.
I suppose if OP has the fitting on hand might as well use it, but it would be my third choice.