Kerdi Shower Drain Question

[TomV8]

Hello there,

In a previous thread of mine, I had some questions about replacing the shower valve and head etc, and it was mentioned by another user that I am required to use 2 inch shower drain for new walk-in shower.

Today, I talked to my county's code inspector and discussed the situation. In my county we are using the 2006 IPC and 417.3 which allows shower waste outlets to be 1.5 inch in diameter. I was told by the county code dude that I can still use the 1.5 pipe but the reducing has to be done before the p-trap, so i am thinking of using a 2 to 1.5 bushing. Past that, it's not allowed.

i have attached a diagram that shows my current setup, (not to scale) from what I can view from the tub's access panel. I have a tub/shower that just has an elbow connected to a 1.5 inch drain pvc that runs into a, what appears to be a regular T fitting and then it runs down and out of sight.

I am having a Schluter shower system that uses a Kerdi drain, which accepts a 2 inch pipe. I was then going to have the 1.5 pipe go to a long sweep elbow to reconnect it to the existing pipe.

Would it be better to use a reducer that looks more like funnel instead of the bushing? And should I use something else other than a long elbow to connect with the existing drain pipe?

Does all this make sense? I may not even need to add a p-trap since there is not one currently in view. (I hope there is one just a bit out of view). The home was inspected when built and possibly by the same guy i was talking too, but that was 15 years ago and they don't keep the plumbing plans for only 5 years.

 

[wwhitney]

Yes on the funnel shaped reducer.

The trap in your existing is surely out of view. Your proposed drawing does not have a vent on the trap and is not allowed. You need to figure out how the tub is vented and whether you can reuse that vent for the shower. That may involve lowering the p-trap compared to your drawing, assuming there is clearance.

Cheers, Wayne

 

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[TomV8]

The code inspector said that the vent is probably off of the toilet drain line since it's located only about three feet away. I was/am skeptical about that, but I have never had any problem with drainage with the shower and the house is only 15 years old, so I would expect the codes to be enforced/attempted.

In the next few days I am going to dig through the insulation in my attic to find the vent pipe that hopefully is there. It should be running across the ceiling joists to the main/only vent stack through the roof.

 

[TomV8]

So last night I spent a while in my attic for really the first time ever since owning the house besides popping my head up to look around. By complete chance I found the vent pipe that comes up from the master bathroom under about a foot or more of blown insulation. It connects to the main stack, of course.

I am planning on starting the demo this weekend-temporary cap the water lines to the current valve, remove the tub, tear down the current tile and wall board, removing the mortar bed and cutting out part of the existing subfloor to install the extended drain.

Having access to the sub floor should allow me to find out if there is an actual p-trap and a vent that snakes over to the main bathroom vent. If not, I can install a new p-trap and then run a vent right up the wall and into the attic. Since i know where the current main bathroom vent, it should be pretty easy to connect the two together. Probably just need about 15 feet of pvc pipe. I thought I could place a infrared web cam that i own on a stick and snake that around and hopefully that can gives me a view of areas that i currently cannot see.

I expect to find a p-trap with it's own vent line since the current drain never has a problem especially since it's a huge whirlpool tub and the water flow rate on the roman faucet is pretty crazy. I really just want to verify with my own eyes since I trusted the original builders to install a simple tub, but they completely F'd that up to the point of needing a 360 degree shower curtain to prevent water from running down the wall and straight into our kitchen below. The builders installed a free-standing tub in an alcove, which is a no-no with a shower. As you probably know, free-standing tubs do not have any tile flange like normal tubs. The install is different for alcove tubs too. You install the a normal alcove tub, then the backing board over the flange and then tile over that so the water diverts into the tub. It seems like they installed the wall board first, put the tub in and then tiled. So if the chalk is not 100% sealed, it leaks. and it leaks because the edges of the tub have a large round over. Which is why i'm tearing out the tub and replacing it with a walk-in shower.

Though, since I am going to be removing some of the sub-floor in the shower area and I am also having the rest of the bathroom floor tiled as well, I may try to find the where the shower drain connects to the toilet drain pipe since that has to be at least 3 inches. That way I may just redo the entire 1.5 drainage with solid two inch. I'm going to have extra OSB sheeting, so that will not be an issue.

I also need to take plenty of pictures of all the work so there is no future questions. Including taking pictures and measurements of all the blocking I'm installing in case I ever want to put in hand rails or other items, so I'm not reliant on the backing board for support.

 

[wwhitney]

OK, post again when you have pictures or questions.

To clarify my earlier response, the vent for a trap arm has to be connected before the trap arm falls more than one pipe diameter, which is why the drawing you posted with an elbow and no vent shown is not correct. A dry vent also has to come off vertically and rise (at least 45 degrees above level) until at least 6" above the fixture flood rim.

Cheers, Wayne

 

[Tuttles Revenge]

A funnel is the better option, but most of our inspectors only allow a bushing, so that you can't change it later(kind of a dick move if you ask me). Very likely your tub is connected to a 2" drain before tying into the stack.

If you have the opportunity to make that 2" you should. Only 1 shower outlet is allowed for a tub to shower conversion on an 1.5" drain (UPC)

If I understand the drawing, it would indicate that the shower would have a trap directly under it, and a trap that served the existing tub. You definitely don't want to do that. It would be better to Long turn 90 under the shower drain to the vertical drop over the tub trap if you need to keep the shower drain centered. We convert tubs to showers all the time on top of reinforced concrete slabs and have to do it that way.

 

[TomV8]

for whitney: Here is actual picture my above drawing is based off of. What we are looking at is the space behind the tub. To the left of the water pipes is a bumped out interior wall that is about 8 inches deep from the actual inner edge of the exterior. The pipe that goes up is just for the tub drain and not a real vent.

In front of the shower drain is our toilet and then a duel sink vanity and then the drain line goes vertical to the first floor.

I was planning on having the long elbow replace the T fitting that is currently there. Tuttles Revenge: I agree on the long 90 underneath especially since I'm sure that there is a p-trap already installed further down the line. kinda like what they used connected to the bottom of the tub. That is one sharp 90. I just hope I have enough vertical clearance without having to raise the shower floor to cover two opposite facing long elbows. This bathroom is located on my second story and we have engineered I-joists. I am guessing that the p-trap is somewhere in front of the camera.

If you were following my other thread about PEX lines, those water lines need to be moved so they are to the left of the those studs. Right now coming from the shower valve they snake around the tub and connect to the faucet before going into the floor.

 

[wwhitney]

Schluter makes a side outlet Kerdi drain, I believe. And then to turn the tailpiece from horizontal to vertical, only a quarter bend would be required, not a LT90.

That assumes there's a trap directly below the tub waster/overflow tee, as there almost certainly is. But if the you have the clearance below, lengthening the trap arm to move the trap to under your shower drain would be a better option, assuming that doesn't make the distance from the trap to the vent too long (or the fall more than one pipe diameter).

Cheers, Wayne

 

[TomV8]

Schluter makes a side outlet Kerdi drain, I believe. And then to turn the tailpiece from horizontal to vertical, only a quarter bend would be required, not a LT90.

That assumes there's a trap directly below the tub waster/overflow tee, as there almost certainly is. But if the you have the clearance below, lengthening the trap arm to move the trap to under your shower drain would be a better option, assuming that doesn't make the distance from the trap to the vent too long (or the fall more than one pipe diameter).

Cheers, Wayne

They actually do make a side drain. Just found that yesterday. I was planning on buying it, just to be on the safe side. i can always return it if not. I do have to lengthen the drain since we are going from a left sided drain to a center shower drain. It will be centered on 58/ 29 inches. I'll try to lower a camera in the subfloor cut out and see what I find.

 

[TomV8]

Update: I did take a camera and was able to shine down through the opening in the subfloor. The p-trap is located right below and then it turns 90 degrees and probably makes it's way to the main drain line in line with the toilet. There doesn't appear to be another vent but currently there is no way for me to tell this.

But I assume that this is ok since there is one vent a few feet down the line, so it goes, shower, toilet, sink, vent and then the vertical drop to the first floor, right? Per the 2006 IPC codes, it seems like this is fine and I don't need to add another vent. If i'm wrong, please let me know.

My thoughts on upgrading from a 1.5 inch to a 2 inch pipe, is if I do have access through the floor, cutting out the current T fitting on the main drain line and replacing it. Everything until this part seems very doable by me.

 

[wwhitney]

But I assume that this is ok since there is one vent a few feet down the line, so it goes, shower, toilet, sink, vent and then the vertical drop to the first floor, right? Per the 2006 IPC codes, it seems like this is fine and I don't need to add another vent. If i'm wrong, please let me know.

That's a little too vague to say for sure, but may be fine, and there's no particular reason to think it isn't. Once you have it open, come back with a diagram for a proper answer.

Cheers, Wayne

 

[TomV8]

So after everyone's suggestions, i am moving the p trap right off the shower drain and then installing a vent that will go through the ceiling and connect to the existing vent line which goes to the roof stack.

This is the new fittings using to my existing drain let me know if this is a good connection. Thanks

 

[TomV8]

It's a dry vent btw since this is my second floor bath

 

[wwhitney]

No, that doesn't work. The vent connection has to come off before the trap arm falls more than one pipe diameter, that's called the trap weir rule. So you can't have the drop shown on the right with the 45 and the LT90. Why is that there?

To put it a different way, the inside of the "crotch" of the wye, where the vent connects to the wye, has to be at a higher elevation than the bottom of the inside of the trap outlet elbow. (That latter point is the trap weir, the point water first spills out of the trap if you slowly fill it with water).

If the reason for the drop is to accommodate the sweep of the combo (wye + 45) and for no other reason, the IPC allows a san-tee on its back for the vent takeoff.

Cheers, Wayne

 

[TomV8]

Jow about this setup. I need to cut back the one pipe to make everything fit but thos gets the idea across.

 

[TomV8]

Or this

 

[wwhitney]

The second one is wrong, for venting a trap arm you need a san-tee, not a combo. [Notice how much lower the crotch of the combo is than on a san-tee, and that trap weir rule I mentioned.]

The first one is fine, assuming the pipe coming up from the bottom of the picture is the trap arm, and the fall from the trap to the san-tee is less than 1-1/2".

BTW, have you looked at how far the existing 1-1/2" pipe runs, and what it connects to, and how hard it would be upsize it to 2"?

Cheers, Wayne

 

[TomV8]

would have cut out my toilet drain line, which would involve cutting up outside the shower area floor. My problem is i have installers coming Monday and the drain pipe is only like three inches below the subfooor.

I am actually going to have to raise the subfooor by 1x4s amd then another layer of OSB.

This is where I'm at right now. I'm almost too close to my exterior wall where i don't want to drill through the i joists

 

[wwhitney]

That should work and I don't see any plumbing code violations. The horizontal "tail piece" maybe should be minimized, since any organics that accumulate there might be a source of odor. And of course all the horizontals needs 1/4" per foot slope, I'm curious if the side exit Kerdi drain is cast at 91 or 92 degrees, or at 90 degrees?

Cheers, Wayne

 

[TomV8]

Thanks. I am going to have the trap closer to the drain, but I just had a scrap piece of old pipe

Everything would be simpler if I don't add the vent. The existing vent is about 9 linear ft away from the new drain. Only about 2 extra feet away from the old drain. Add the vent or forget it?