How to get this shower drain connected to the main line?

[beerdwolf]

Hey there folks, im trying to solve this conundrum. Im DIY.
This is a 3" main dropping 1/4" per foot and making a long turn into a vertical stack into a slab a plumber put in for ny home addition. There is a cleanout in the vertical. The branch you see off to the left is the bathroom sink, with another sink about 5ft further in a straight line. There is a toilet at the end of this 3" pipe. Both sinks are vented via a 2" that goes out the roof. First vent is right on the other side of that joist.

i need tk connect the shower to this, its that hole you see. Its about 4' from the vent.

Initial plan was to drop from the p trap vertically into the main, but I think that's an s trap no matter how I do it. I don't understand the s vs p on a wet vent. Is this pipe all big enough to avoid an s trap if I run the trap arm 6" or so before dropping into the main with a wye?

I thought of one solution if not, as I have a wall between the toilet and shower drain, if I drop from the shower into a 22.5 I can get more vertical space, put a sanitee upside down and run a vent back and up into the wall to connect into the existing vent, then use a wye to drop into the 3" after the p.

I think i also have room to run over the 3" and connect into the vertical portion of the vent thats already in place also, either before or after the p trap.

 

[beerdwolf]

 

[Sponsor]

 

[beerdwolf]

I also just realized I used a sanitee on the drop on the left and need to swap it out, doh.

 

[wwhitney]

If you are trying to wet vent both the WC and the shower from your double lav, then the order of connections on the 3" pipe starting at the closet flange and going downstream needs to be:

Closet flange
At least one lav (could be both) on a 2" drain line within the first 6' of the 3" pipe (counting both vertical and horizontal portions)
Shower

Looks like you have the wrong order at the moment, and it's not clear if the lav comes in within 6' of the 3" pipe.

Then for the shower connection, the trap outlet has to be at approximately the same elevation as the 3" line. So you need room in the joist bay for the shower tailpiece to come in alongside the horizontal 3" line. The limitation is that the fall from the shower trap to the wye with the 3" line (actually the joint in the wye between the 2" side branch and the 3" line) is limited to one pipe diameter of the trap, or 2".

If you need to rearrange part of what's shown in your picture, a dimensions floor plan showing the locations of the fixture, the stack below, and the joists would be the easiest way to discuss layout.

Cheers, Wayne

 

[beerdwolf]

If you are trying to wet vent both the WC and the shower from your double lav, then the order of connections on the 3" pipe starting at the closet flange and going downstream needs to be:

Closet flange
At least one lav (could be both) on a 2" drain line within the first 6' of the 3" pipe (counting both vertical and horizontal portions)
Shower

Looks like you have the wrong order at the moment, and it's not clear if the lav comes in within 6' of the 3" pipe.

Then for the shower connection, the trap outlet has to be at approximately the same elevation as the 3" line. So you need room in the joist bay for the shower tailpiece to come in alongside the horizontal 3" line. The limitation is that the fall from the shower trap to the wye with the 3" line (actually the joint in the wye between the 2" side branch and the 3" line) is limited to one pipe diameter of the trap, or 2".

If you need to rearrange part of what's shown in your picture, a dimensions floor plan showing the locations of the fixture, the stack below, and the joists would be the easiest way to discuss layout.

Cheers, Wayne

Hey Wayne,

The closet flange is the start of that 3" there, its about 2' to the wye and 2' above that is the 1st lav, 5' beyond that lav is another. Both are on 2" all the way to the roof - the only 1.5" in the system is the stub out of the walls. All stud bays open still.

Hopefully this is what you're looking for - I'm no artist.

The joists are 16" - there is not enough room to put a combo wye in there for a horizontal entry, though the 3" line sits about 6" above the ceiling level at the shower drain so I can drop the p trap down below the 3" a bit.

I could also put the p trap right under the shower and have the exit turn 90 above the 3" and tie it in to the 1st vented lav if that's a workable option.

 

[wwhitney]

OK, your floor plan clarifies the layout (I hadn't realized your photos were both facing upstream), and it's fine, once you change the fitting where the 2nd lav joins to a combo.

On the original question, the conventional way to join the shower and the 3" WC/lav drain in your situation is via a configuration you might call an "upright wye," although used flat in a horizontal plane (at 2% slope). That's a wye, with a street 45 in the branch inlet, with the 45 inlet parallel to the wye straight inlet.

If you do that in ABS via a 3x3x2 wye and a street 2" wye, then the two inlets will be 4.75" apart center to center. So the total width, ignoring hubs, will be 0.5*(3.5+2.375)" = a little under 3" wider. I.e 7.75" wide. So that should fit in a 16" o.c. joist bay no problem.

I believe the u-bend on a 2" trap is 5" c-t-c. So as long as the 3" line does not pass directly under your shower tailpiece, you can drop the shower tail piece straight down into a u-bend, and rotate the u-bend so its outlet is 4.75" c-t-c from the 3" line. Then point the elbow trap outlet to be parallel to the 3" line, and the center line of the outlet should be at least 1/8" higher than the 3" center line but otherwise close to it in elevation. Then a short pipe segment and the upright wye configuration.

If at present the hub on the u-bend would actually interfere with the 3" pipe, then you'll need to jog one or the other. If you have the height available you could jog the tailpiece with a pair or 22.5s or 45s. Better is probably to jog the 3" line. I.e. maybe at the closet flange turn the closet bend 22.5 or 45 degrees away from the lavs, then use an elbow to turn parallel to the joists not directly under the shower hole.

Cheers, Wayne

 

[wwhitney]

P.S. In case it wasn't clear, the maximum height the shower trap outlet center line could be above the 3" center line is about 2". That's because the shower trap arm can fall at most one pipe diameter (2") before being vented; otherwise the trap could siphon. And the vent for the shower trap is the 3x3x2 wye.

So you can roll the "upright wye" configuration up a little if necessary, e.g. to keep the u-bend from poking through the ceiling. But you can't roll it up so far that the shower drain enters the 3" line from above.

Cheers, Wayne

 

[beerdwolf]

I can't fit a combo y in that 1st lav space so I'll probably convert it to a dry vent - you can kind of make out the orange in the picture but it was the original drain location - I can leave the sanitee in place if its not part of a drain and just going up to vent right?

So a 3x2 combo wye touches the next joist - I was thinking of jogging the closet anyway because where it turns down into the main sewer line its against the far side of the joist bay but the toilet is centered so that would be easy enough to do.

I didn't think of flipping the 45 on a normal wye backwards, that should fit just fine I think. Probably because I have a 3x2 combo wye sitting on the floor already.

I can jog the shower tail as well.

Simplest solution seems to be the 3x2 wye with a 45 angled back towards the shower, then I just angle the P trap exit into the 45 and good to go If I'm understanding correctly

 

[wwhitney]

I can't fit a combo y in that 1st lav space so I'll probably convert it to a dry vent - you can kind of make out the orange in the picture but it was the original drain location - I can leave the sanitee in place if its not part of a drain and just going up to vent right?

No, not under the UPC. The san-tee needs to come out.

You don't need both lavs to be 2", so if the upstream one is 2", the downstream one could be 1.5" with a 1.5" vent. In case a 2x2x1.5 combo fits.

Another option that might fit would be to put a 45 on the upstream lav, and put a 45 on the downstream lav near the subfloor, and have them both enter an upright wye whose barrel is at 45 to the joists in plan, and then go through the joist at a 45 to a wye on the 3" line.

If that doesn't fit then there are still plenty of other options, just more indirect. E.g. the downstream lav could connect to the 3" line separately.

Simplest solution seems to be the 3x2 wye with a 45 angled back towards the shower, then I just angle the P trap exit into the 45 and good to go If I'm understanding correctly

Yes, that would be fine and saves a 45 over the "upright wye" I suggested. There is a minimum length of a trap arm, which is 2 pipe diameters, or 4", but it's measured from the trap outlet to the "crotch" of the wye. So it probably would be enough even if the hubs touch, but double check. You can always swing the u-bend around to point away from (perpendicularish) the 3" line to get a little extra separation if needed.

Cheers, Wayne

 

[beerdwolf]

Will be picking up fittings today and making adjustments then will report to close the loop

 

[beerdwolf]

Here is the dry fit, measurement will change ever so slightly as everything isn't jammed all the way into the collar

The u is on the center with the 3", the 90 exit of the p trap is less than 2" from center, and I've got a 1/2" from the ceiling line.

Any issues? I'd like to rotate that y up a bit more if it's doable

 

[wwhitney]

The offset is OK. If the shower drain dropped straight down, would it or the trap hub actually hit the 3" line? If not, you can skip the offset and just rotate the u-bend, so the p-trap ends up not planar.

On rolling the 3x3x2 wye, in the diagram below, the lefthand red elevation has to be higher than the righthand red elevation. The right is meant to be the elevation at which water first falls out of the trap as you fill it up, i.e. the bottom inside of the outlet elbow of the trap. The left is meant to be the elevation at which the top of the 2" pipe enters the 3" pipe, i.e the top inside of the crotch of the wye; that is the point at which if the 2" pipe fills with water, it would be cut off from the air space at the top of the 3" pipe. As long as the lefthand elevation is above the righthand elevation, the trap can't siphon. So that's a requirement.

It looks like you can't rotate it any more and may have gone too far. Or maybe you're just OK, and I drew them inaccurately on the photo.

Cheers, Wayne

 

[beerdwolf]

And on that wye, 2x1.5 doesn't fit, but how does this function (I know it looks bad.)
Put a y horizontal and then 90 around to enter on the side

 

[beerdwolf]

The offset is OK. If the shower drain dropped straight down, would it or the trap hub actually hit the 3" line? If not, you can skip the offset and just rotate the u-bend, so the p-trap ends up not planar.

On rolling the 3x3x2 wye, in the diagram below, the lefthand red elevation has to be higher than the righthand red elevation. The right is meant to be the elevation at which water first falls out of the trap as you fill it up, i.e. the bottom inside of the outlet elbow of the trap. The left is meant to be the elevation at which the top of the 2" pipe enters the 3" pipe, i.e the top inside of the crotch of the wye; that is the point at which if the 2" pipe fills with water, it would be cut off from the air space at the top of the 3" pipe. As long as the lefthand elevation is above the righthand elevation, the trap can't siphon. So that's a requirement.

It looks like you can't rotate it any more and may have gone too far. Or maybe you're just OK, and I drew them inaccurately on the photo.

Cheers, Wayne

View attachment 90887

The offset is just there for now, I'll adjust that to fit best once the wye is good plenty of play in the 3" pipe to move it where it needs to be + nothing is glued yet so I can move the p trap over too - I just need to make sure that wye is good to go I think I've got it now though, should be room to make it happen - I couldn't job the 3" because you can sort of see theres maybe 3" from the top of that 90 to the bottom of the toilet flange.

I'm at 1/4" now - I may as well raise the 3" so that flange meets the 90, its a 9' run so it will go up to something like 1/2" per foot. I don't think that will add much stress to the other end

 

[beerdwolf]

Hey, here is the completed product, much appreciated for the help!