Low clearance toilet drain

[FrankBranch]

We live in a log home with a finished loft. At some point a bathroom was added to the loft, the waste drain is plumbed with 3” PVC pipe, with the flange screwed to the subfloor. I believe the plumber used an inside flange, since the toilet is very hard to set due to the horn tending to interfere with the inside of the flange.

The structure under the bathroom is 4”x 8“ open beams with 1” tongue & groove (which is what you see underneath) overlaid with a ¾” OSB subfloor. The area under the bath was a former laundry room, with the overhead mechanicals concealed with a rather unsightly drop ceiling (made all the worse by periodic leaks from the poorly sealing toilet).

We are starting a remodel where we are expanding the kitchen into the former laundry area. We plan to box in the space between the 4”x8” beams to hide the plumbing, but that means the waste drain under the toilet needs to be as close to the underside of the floor as possible, that way the approx 5’ piping run with ¼” / foot drop stays well within the 8” area established by the beams. The current setup uses a 3” elbow with a low heel inlet, which picks up a lavatory drain.

What are some tricks for installing a toilet with very little underfloor clearance? Is there a “street” configuration closet flange that would fit directly into elbow? A solution that makes the upstairs toilet set easily would be a bonus!

 

[Reach4]

The structure under the bathroom is 4”x 8“ open beams with 1” tongue & groove (which is what you see underneath) overlaid with a ¾” OSB subfloor.

Subfloor, by definition, is not the layer on top. You might make a sketch.

Tennessee uses IPC. IPC allows 3 inch and bigger to use a 1/8 inch per foot slope. You can paint PVC if some pipe is exposed.

What are some tricks for installing a toilet with very little underfloor clearance? Is there a “street” configuration closet flange that would fit directly into elbow?

That is called a "spigot" closet flange, where the output is the same size as a pipe. There are "inside" flanges made to fit inside a pipe, and "outside" flanges also.

A closet bend (closet elbow) will typically have 3 inch horizontal output and a 4 inch input. In addition to glued toilet flanges, there are compression flanges. With glue you needed to get it right the first time.

 

[Sponsor]

 

[Terry]

A toilet should never be plumbed to a santee on it's back. A lo-heel is a santee that is used on the vertical, not the horizontal.
The toilet gets a 90 bend and a wye downstream for the lav.

In this case I used a medium 90 with a spigot closet flange.

 

[FrankBranch]

Here’s a sketch of the floor, it’s a stack of 1” T&G poplar with OSB on top, total thickness is 1 ¾”.

I have no idea if the current work is to code, we live in a very rural area (no code / inspection) and the folks that call themselves “plumbers” out here really do little to advance the craft (first one was on pills, abandoned the job, second one left town with an uncrimped PEX fitting under a sink that ruined a floor).

Here’s a photo of the current underside.

 

[Terry]

That is not done anywhere else. The poop lands straight down and spreads both ways.
It should be an end of line 90 and downstream of that a wye for the lav.

 

[wwhitney]

If the goal is to raise the 3" horizontal line as high as possible, I think the best you can do would be to use a 3" quarter bend (center-line radius is 3", ex hubs of 1-1/2" depth) and a 3" spigot end closet flange, such as this one (although you don't need the knockout unless you are going to be pressure testing your work):

https://www.supplyhouse.com/Sioux-C...Knockout-Flange-w-Stainless-Steel-Swivel-Ring.

You'd need to enlarge the hole in your floor for the 3" hub and perhaps part of the bend of the 3" elbow. You don't specify the thickness of your bathroom finish floor, but the flange is about 1/4" - 5/16" thick, I believe, and the spigot end starts 1/2" down from the top of the flange. So you'd want the end of the hub of your quarter bend to be about 1/4" below your bathroom finish floor so that the flange can sit on top of the finish floor. That should work as long as your finish floor is under 1" thickness; if it is thicker, you'll need an extended spigot end flange, like this one, which you can cut to length:

https://www.amazon.com/Canplas-193617SS-Closet-Stainless-Extended/dp/B00PCRAIOO

Of course you'll have to raise up your lavatory drain as well. The proper way to join the WC and lavatory drains on the horizontal is to bring them side by side (at the correct spacing), so you'll have to relocate the lavatory drain to one side. Then you join them with a 3" reducing wye and a street 45 elbow into the reduced branch of the wye, with the inlet parallel to the 3" wye inlet. (Or if they are farther apart, a regular 45 elbow).

Cheers ,Wayne

 

[FrankBranch]

If the goal is to raise the 3" horizontal line as high as possible, I think the best you can do would be to use a 3" quarter bend (center-line radius is 3", ex hubs of 1-1/2" depth) and a 3" spigot end closet flange, such as this one (although you don't need the knockout unless you are going to be pressure testing your work):

https://www.supplyhouse.com/Sioux-C...Knockout-Flange-w-Stainless-Steel-Swivel-Ring.

You'd need to enlarge the hole in your floor for the 3" hub and perhaps part of the bend of the 3" elbow. You don't specify the thickness of your bathroom finish floor, but the flange is about 1/4" - 5/16" thick, I believe, and the spigot end starts 1/2" down from the top of the flange. So you'd want the end of the hub of your quarter bend to be about 1/4" below your bathroom finish floor so that the flange can sit on top of the finish floor. That should work as long as your finish floor is under 1" thickness; if it is thicker, you'll need an extended spigot end flange, like this one, which you can cut to length:

https://www.amazon.com/Canplas-193617SS-Closet-Stainless-Extended/dp/B00PCRAIOO

Of course you'll have to raise up your lavatory drain as well. The proper way to join the WC and lavatory drains on the horiozntal is to bring them side by side (at the correct spacing), so you'll have to relocate the lavatory drain to one side. Then you join them with a 3" reducing wye and a street 45 elbow into the reduced branch of the wye, with the inlet parallel to the 3" wye inlet. (Or if they are farther apart, a regular 45 elbow).

Cheers ,Wayne

Thanks, Wayne! Good to see you refer to SupplyHouse - love those folks, easy to navigate site, huge selection, great service, reasonable service. You refer to a “quarter bend” - is that an elbow like this:

https://www.supplyhouse.com/Spears-P300-030-3-PVC-DWV-90-Elbow

Will try to post another photo below, says it’s too big

 

[FrankBranch]

Believe this is the Y y’all are suggesting to tie the sink into the line from the toilet:
https://www.supplyhouse.com/Spears-P601-337-3-x-3-x-1-1-2-PVC-DWV-Wye

Here is the rest of the plumbing. Trying to compress the drain lines to a 4” wide region along the wall. Still trying to figure out how to handle the shower drain, may try to elongate the hole till it’s about 1 ½” from the wall and use something like this:
https://www.supplyhouse.com/Spears-P417-337-3-PVC-DWV-Sanitary-Tee-w-1-1-2-Right-Side-Inlet

To pick up the shower drain in the 1 ½” port, bring the shower drain in the 3” side port and run the vent out the other side of the T. At least it’s an easy place to work, rather on my belly in a crawl space.

 

[Terry]

That 3" x 1.5" wye works.
The upstairs shower should have dropped into a combo or wye fitting and not the santee that is there.

Does the shower have a p-trap and vent?

Does the lav have a p-trap vent?

 

[Reach4]

If you use a closet bend, you can use a 4 inch outside or inside closet flange. Cut down to fit your needs. Feeds into a 3 inch pipe. Charlotte 330 shown.

 

[FrankBranch]

That 3" x 1.5" wye works.
The upstairs shower should have dropped into a combo or wye fitting and not the santee that is there.

Does the shower have a p-trap and vent?

Does the lav have a p-trap vent?

The shower has a P-trap of sorts (shower is on a raised platform, drain runs horizontal about 4’, trap is made out of 4 - 90 degree L’s. Not sure about the vent, haven’t opened that up yet. Lavatory has a P-trap underneath, separate vent to outside. It’s the only separate vent, everything else is tied into the 3” vent in the photos I posted.

 

[Tuttles Revenge]

A 4x3 Closet bend that Reach4 references is The fitting to use for the toilet. In this scenario it can be installed with its horizontal hub snug to the bottom of the subfloor for maximum height which would gain at least 1.5-2" of clearance.

 

[wwhitney]

A 4x3 Closet bend that Reach4 references is The fitting to use for the toilet. In this scenario it can be installed with its horizontal hub snug to the bottom of the subfloor for maximum height which would gain at least 1.5-2" of clearance.

Thanks to you and Reach4 for pointing it out.

The big advantage of the spigot end 3x4 closet bend is that the insider corner is square. That lets you push it up against the bottom of the subfloor with just a round hole above. You could do the same thing with a 3" quarter bend or a hub end 3x4 quarter bend, but you'd need to hog out additional material for the inside curve of the fitting. [Edit: and you'd still need 2-1/2" from the finish floor above to the top of the horizontal hub, so you might not be able to push it up all the way.] The outside radius of curvature of all 3 of those fittings looks to be the same.

The spigot end 3x4 closet bend is also 1/2" longer on the inlet than a 3" street quarter bend, which is helpful if your total floor build up exceeds 2-1/2" and you want the top of your closet bend near flush with the finish floor.

So in the picture, with the quarter bend hub up against the subfloor, the outlet hub is about 2-1/2" clear below the subfloor. Recessing the hub only of a 3" quarter bend into the subfloor will reduce that to 1". And then the above method would let you get it down to 0".

Cheers, Wayne

 

[FrankBranch]

Great thoughts folks! So I ran some numbers, they are based on Charlotte DWV fittings since they had a fairly comprehensive catalog with dimensions. I assumed an installation where the hub connecting to the 3” drain line was flush against the underside of the floor, then calculated where either the end of the hub or spigot ended up relative to the floor top surface.

For a sanitary ¼ bend, the top edge of the hub will be 0.845” above the finished floor
For a street ¼ bend, the spigot end will also be 0.845” above the finished floor
For a closet bend the top edge of the hub will be 1.032” above the floor (the 4” hub is 1.75” deep)
For a closet bend with a street end, the spigot end will be 1.282” above the finished floor

This assumes all fittings are used stock, might be able to shorten the hub / spigot a bit since there is no pressure or mechanical stress on the joint. Any other ideas?

So I next considered some “non traditional” and not to code approaches
Using a vent L the edge of the hub will be 0.343” BELOW the finished floor
Using a street vent L, the spigot end will be 0.218” BELOW the finished floor
Using a vent T, the edge of the hub will be 0.343” BELOW the finished floor. Thinking behind the vent T is the unused port could be sealed with a screw in plug and be used as a clean out, and it softens the bend around the corner. What kind of trouble am I bringing upon myself with this approach?

 

[Tuttles Revenge]

The spigot x hub closet bend is installed so that the 4" spigot/pipe size is long through your finished floor and cut at time of flange installation either prior to tile going down or on top of your finished floor.

The only 2 other fittings that could compare would be a 3" vent 90 and the 90 from a 3" glue trap if you can find one.. basically a street vent 90. But that would be like doing a bunch of unnecessary work to create what a closet bend does. and then you're limited to whatever closet flange you can fit.

 

[FrankBranch]

The spigot x hub closet bend is installed so that the 4" spigot/pipe size is long through your finished floor and cut at time of flange installation either prior to tile going down or on top of your finished floor.

The only 2 other fittings that could compare would be a 3" vent 90 and the 90 from a 3" glue trap if you can find one.. basically a street vent 90. But that would be like doing a bunch of unnecessary work to create what a closet bend does. and then you're limited to whatever closet flange you can fit.

Thanks! Do they make a closet flange that has a clear center that slips over the 4” spigot end? Could basically slide it down till the flange was on the floor, then cut the spigot end off flush? What kind of grief would I get into using a vent 90 with a spigot closet flange? Are there issues with clogging due to the tighter bend under the toilet?

 

[wwhitney]

For a sanitary ¼ bend, the top edge of the hub will be 0.845” above the finished floor

That doesn't compute for me.

Charlotte's catalog says a 3" quarter bend (not long turn), less hubs, has a rise of 3-1/16" from center-line of horizontal outlet to top of inlet. The hubs are 1-1/2" deep and have a 4" OD. So the distance from the top of the outlet hub to the top of the inlet hub is 3-1/16" - 2" + 1-1/2" = 2-9/16".

As you've specified a sub floor build up of 1-3/4", the top of the inlet hub would be 13/16" above the top of the subfloor, or 0.81". And less than that above the finished floor.

Anyway, Tuttle's idea is the best, go with it.

Cheers, Wayne

 

[Reach4]

Thanks! Do they make a closet flange that has a clear center that slips over the 4” spigot end? Could basically slide it down till the flange was on the floor, then cut the spigot end off flush?

That would be an outside glue closet flange, except I think the spigot end should be cut to be below the floor.

Another flange to consider would be a C40320 3 pipe x 2 depth over a 3 inch spigot
https://www.homedepot.com/p/JONES-S...-in-Cast-Iron-Closet-Flange-C40-320/100168417
or C40420 over a 4 inch spigot. I suspect the description is off on this listing: https://www.homedepot.com/p/JONES-S...-on-Cast-Iron-Closet-Flange-C40-420/100175841

https://www.homedepot.com/p/JONES-S...-Closet-Flange-with-Test-Cap-C40425/313740740 is similar.

Either way, I would want the closet flange in hand before cutting the pvc.

These closet flanges seem to be variously called Code Blue and Plumb-best The 4-inch ones come in 2, 3, and 4 inch depths. I don't know of a nice dimensioned drawing to go with them.

https://www.oatey.com/products/oatey-cast-iron-closet-flange-279105324 is similar.

What these have in common is outside compression, rather than gluing. With this, you get easy do-overs.

The most common thing to put into a 4 inch spigot/pipe is a 4x3 inch closet flange that glues inside of a 4 inch spigot/pipe or outside of a 3 inch spigot/pipe. If gluing, I would want a stainless steel ring for durability. Oatey PVC Flange in the Toilet Flanges department at Lowes.com is typical of those.

 

[Tuttles Revenge]

Thanks! Do they make a closet flange that has a clear center that slips over the 4” spigot end? Could basically slide it down till the flange was on the floor, then cut the spigot end off flush? What kind of grief would I get into using a vent 90 with a spigot closet flange? Are there issues with clogging due to the tighter bend under the toilet?

You can do all kinds of weird things that might work...If you want to experiment, go for it. I've been down every one of those fitting combos and can get them to work.. But I don't feel like going thru the Work of describing the minutia here online.. for that you would have to be buying the beers.

The beauty of the 4x3 is that a straight 4x3 closet flange is designed to fit Inside the closet bend.. in your case you may end up cutting the flange to just 1" or so after the bend is cut flush with the finished floor. Or if you wanted to do some extra work and make sure you have clearance around the bend, you can install a 4" closet flange to the outside of the bend.

 

[FrankBranch]

That doesn't compute for me.

Charlotte's catalog says a 3" quarter bend (not long turn), less hubs, has a rise of 3-1/16" from center-line of horizontal outlet to top of inlet. The hubs are 1-1/2" deep and have a 4" OD. So the distance from the top of the outlet hub to the top of the inlet hub is 3-1/16" - 2" + 1-1/2" = 2-9/16".

As you've specified a sub floor build up of 1-3/4", the top of the inlet hub would be 13/16" above the top of the subfloor, or 0.81". And less than that above the finished floor.

Anyway, Tuttle's idea is the best, go with it.

Cheers, Wayne

Here’s my arithmetic
C/L of fitting to bottom of hub - 3 1/16”
C/L of pipe to outside of mating hub (3 ½” / 2 + 0.218” hub thickness) = 1.968”
Assuming that the C/L of the fitting and the pipe are the same, the distance from the outside of the hub on the drain pipe to the bottom of the fitting hub is 3 1/16” - 1.968” = 1.094”
To this we add 1.5” of hub and subtract 1.75” of floor buildup to get where we are with respect to the finished floor which puts the top of the hub 0.845” above the floor.

Anyway, think I will go with the street closet bend, buy extra parts and plan to modify as need be.