(Pic) Need to wye out from 3” line to add another 3” like with 9” of space

[BrendonTW]

Hello all, new here. I’m adding a second toilet to my second floor of my house. The new toilet is going about 5 feet from the existing toilet in a new bathroom. The waste line is a 3 inch line. The problem that I am running into is there were additional joists installed during construction to support the existing toilet and I only have about 9 inches of space to work with. When I measure the width of a 3 inch wye with a 45° street elbow, I come up with about 11 or 12 inches. Tilting the Y up to make it narrower interferes with my ability to keep proper slope. The joists are only 7 1/4 inches tall, so drilling a 3 inch hole through them is out of the question.

 

[Reach4]

Let's call the top of your picture north. Are you saying that the picture shows the bottom of your current toilet, and you want to put an additional toilet due north of the existing one?

There are some good toilet flanges with an output like a pipe at 45 degrees. The Oatey # 436652 is shown.

Could you feed that into a wye? I don't know what the venting considerations are. Sioux Chief has the 889-45AM https://www.siouxchief.com/docs/def...loset-flange---dropkick.pdf?sfvrsn=69b13a37_8

 

[Sponsor]

 

[BrendonTW]

Sorry, should have been more clear. Attaching another picture to clarify.

The rear stool wall is perpendicular to the joists, so I could mount the center of the stool directly in line with the existing 3", or I could move it in the picture to the left, essentially anywhere in that 9" of space I have to work with. The furthest right (directly in line with existing 3") is closest to an existing wall and it's still 15" off the wall. The water closet walls have not been framed yet, so I can set the flange in the ideal spot and then frame the room for equal space on both sides of the stool.

That flange might prove to be a solution, but I would need to drop immediately through the flange into a wye, with the exit side towards the main house stack and the inlet side coming from the other stool. Is that allowed - to go straight from a 45" flange into vertical wye? if this is allowed, the only thing that would possibly prevent this would be the height inside the floor space which is only 7.25". Not sure if it would fit, would be close.

 

[Reach4]

That flange might prove to be a solution, but I would need to drop immediately through the flange into a wye, with the exit side towards the main house stack and the inlet side coming from the other stool. Is that allowed - to go straight from a 45" flange into vertical wye?

I think so. I am not a plumber.

It don't know if it would fit.

 

[BrendonTW]

Thanks for pointing me to that flange. Any plumbers know if this is acceptable?

 

[BrendonTW]

I looked at dimensions for a 3” wye and I don’t think it’ll fit vertically or horizontally. It seems like the only option is a sanitary tee on the existing stool. I know that isn’t allowed. Any suggestions?

 

[wwhitney]

So, I see a fundamental problem: if your current toilet is 12' from the stack, and the new toilet is 6' farther, that's 18' from the stack. At 1/4" / ft drop, that's a 4.5" drop. The outer diameter of 3" plastic pipe is 3.5", for a total vertical extent of 8". That won't fit within your 7.25" joist space.

Once you figure that part out, I think you are going to have to use a DWV material other than plastic for the critical configuration of fittings, in order to get everything to fit within your joist bay. Generally a given configuration of DWV fittings requires the most space in Schedule 40 plastic, sometimes a bit less space in no-hub cast iron, and generally a fair amount less space in copper.

I believe the two toilet drains can't join until after the vent takeoff on the downstream toilet; hopefully your new toilet drain will fit underneath that existing wye for the vent takeoff. So after that point, you can join them with a configuration called an upright wye. That's similar to a combo tee-wye, except the street 45 inlet is parallel to the run of the wye, rather than perpendicular.

A 3" plastic upright wye is about 5.9" center to center on the two parallel inlets, so with 3.5" diameter pipe it won't fit in your 9" joist bay unless it is rolled up a bit. If you are lucky, your elevations will work out to allow that to happen.

In cast iron, Charlotte NH 21A is a single piece upright cast-iron wye that is 5.5" c-t-c in the 3" size. So that should just fit in your 9" wide joist bay, if you can find one.

If you go to copper, a street 45 and wye will make up a 3" upright wye that is only 4.1" c-t-c.

Cheers, Wayne

 

[BrendonTW]

Wayne, you have been helping me over on the John bridge forum for reinforcing the floor. Funny to run into you here but I’m glad I did!

So I was incorrect, the current stool is 6’ from the stack and the new stool is about 5’ from the existing one. So actually only 11’ run.

From the sound of it, I’m going to have to find a plumber to do the copper fitting for me as it is the only thing that will fit.

That vent line coming from the wye after the toilet drain is actually a wet vent coming from the existing bathroom vanity. I can pretty easily tie into that by just going up into the wall and tying into that upright that goes into the attic.

 

[BrendonTW]

On the same note, a quick google search of 3” copper upright wye delivers no results that look correct. Will it be possible to find a plumber who can get one of these things?

 

[wwhitney]

In copper the dimensions I provided are for using two pieces, a wye and a street 45.

In cast iron, there is a one piece upright wye, and it is much more compact than two pieces.

In PVC, there is an upright wye fitting, but it is only about 1/8" more compact than a wye and a street 45.

What is the vertical dimension from the underside of the subfloor to center line of the existing 3" drain, just downstream of the existing wye? Are you confident the existing 6' run has the proper slope?

Cheers, Wayne

P.S. In my state's plumbing code (based on the UPC), a toilet drain requires a minimum 2" vent line. Not sure which code you are on, and whether the IPC is the same.

 

[BrendonTW]

Vertical distance is approximately 4.25" from bottom of subfloor to center line of existing copper line, just past the existing wye.

I am not completely confident in the current slope, but by visual it looks right. I can take measurements later today.

If I were to order the nh 21a cast iron wye, can I use fernco fittings to adapt to the downstream copper, existing toilet copper, and new pvc upstream for new stool? Seems kind of rigged, but if it is without considerable threat it would make this project a lot more simple!

 

[Tuttles Revenge]

Can you post a Plan View of what you're trying to do?

A plastic DWV wye w/ a street 45 is 8" from center of pipe to edge of the 45. in order for you to fit plastic fittings in, you would need to invert the wye and have 6" of space from the center of your horizontal run to the sub floor.

Copper DWV fittings will require skill with a torch and installation made much much easier with lead solder, which may be hard to come by. Not sure how much better they may fit in that space.

If your stack is in that wall in the picture, you're probably better off cutting into the vertical stack and bringing a new stack next to it in that same joist bay.

 

[wwhitney]

Two comments:

1) With the 4.25" vertical measurement you provided, I'll assume it's about 1' downstream of your existing toilet. So at the new toilet location, 6' upstream from there, the lowest you can be when you turn horizontal is 2.75" below subfloor to center line. Something to keep in mind when you figure out what toilet flange/closet bend fittings to use.

I assume there is a wall between the two toilets, so that under the wall you can install a 3x2 combo with the side branch vertical to bring a 2" vent up into the wall?

2) To combine your new toilet drain with the existing 3" copper drain, you'll need to cut out a section for a new wye. If the 1-1/2 drain coming into the existing wye is not moving, then the two remaining ends of your 3" copper drain will be fixed longitudinally, which limits your options for connecting the new wye. You can either do everything in copper and use copper slip couplings, or you can use shielded rubber couplings. If you choose to use shielded rubber couplings, I don't think it matters whether the material between them is a copper fitting or a cast iron fitting.

If your new toilet drain is over living space, that would be an argument for using cast iron for all your new drain work.

Cheers, Wayne

 

[WorthFlorida]

From IPC, Aug 2015.

 

[wwhitney]

Thanks, my experience is with the UPC, but it appears Oklahoma uses the IPC. I find it a bit odd that the two codes can't agree on the minimum slope for a 3" drain line.

Cheers, Wayne

 

[WorthFlorida]

It's the absolute minimum but this short distance 1/4" is better but it gives a little wiggle room.

 

[Tuttles Revenge]

Why not open up the next joist bay and drill another hole for the new 3" branch? It would be a fairly long 3-5/8 hole since the pipe would pass at a 45° angle, but with proper gusseting it would be fine.

 

[Reach4]

The joists are only 7 1/4 inches tall, so drilling a 3 inch hole through them is out of the question.

Why not open up the next joist bay and drill another hole for the new 3" branch? It would be a fairly long 3-5/8 hole since the pipe would pass at a 45° angle, but with proper gusseting it would be fine.

Interesting. Do you think that doubling up using screw and glue would be plenty strong?

 

[WorthFlorida]

Why not open up the next joist bay and drill another hole for the new 3" branch? It would be a fairly long 3-5/8 hole since the pipe would pass at a 45° angle, but with proper gusseting it would be fine.

The largest hole allowed in a 2x8 joist is 2.4". Not sure if sistering another joist to it would allow for a larger hole if space is not tight.

 

[Tuttles Revenge]

I'm not an engineer, so that limits my advice to anecdotal experience. If that were my project I would drill it once my contractor figured out a patch for the structure which from my experience is typically a long full height plywood attached to both sides or 2x material attached to the bottom under where our hole is drilled.