I have a powder room (sink & toilet) in my basement on a concrete slab. It is not plumbed for the shower I want to add. What is the best way to add a shower drain? I'd prefer the minimum of concrete cracking.

As you walk into the existing powder room (6' wide by 5' deep) you are facing the wet wall, which is a generous 8 1/2". The toilet is on the left and the sink on the right. The waste stack runs up the wet wall between them. The ceiling is 10'.

Behind the right wall is a large closet. I intend to move this wall back 42", and use this space for a shower. I know the hard way is to break up the concrete, add a P-trap below the shower and pipe over to the stack, dry-venting the same way as the sink. And the really cheap way would be to raise the shower up on a platform enough to hold the P-trap.

I'm looking for ideas on a sort of compromise. For example, instead of the drain in the center of the shower, I could put it next to the wet-wall, or even in the wet-wall. (I'll be building up the pan myself the old-fashioned way.)

Is there any sort of device I could put in the wet-wall that would substitute for a P-trap? For example, how about a pump and a check-valve with a rubber seal? I could pump the shower water up through the check-valve and over to the stack, so that there would always be a water column above the closed valve. Or maybe I could pump the water up a foot, turn it sideways, add a P-trap and vent? What kind of pump would best handle shower volume, with only a 1' head?

Another idea I had was to cut out just enough of the concrete to put the P-trap below the slab, but have the pipe to the stack be above the slab in the wet-wall. This way the shower pan would only have to be thick enough to cover the pipe plus the 1/4" per foot slope. I could further reduce this height another inch by using a flat pipe or six 1" pipes instead of a 2" pipe.

Imagine the shower pan is only a few inches above the bathroom floor (which I can raise an inch before I tile it.) The shower floor slopes gently to the left, and there's a grilled slot where it meets the wet-wall. Behind this grill is a regular P-trap, which drains with the proper slope into the waste stack, and is dry-vented up through the wet wall.

Of course, I can leave an access panel in the wet-wall to get at whatever monstrosity I put in there. (Maybe I should have made my user name "Poe".)

I'd appreciate any ideas or pointers to products. Then I can run them by our city inspector and see if any will fly.

Thanks.

The right way is the best way. Breaking concrete is hard work and messy but fairly cheap to replace and easy to finish over with tile or other flooring. If you are consulting with your local code official I am sure he will want a dry vent but an air admittance valve is legal and will work fine. (you will need an access panel for it though)

If you do it right you will always be proud of your decision- - but if you go cheap you will regret it every time you walk in the bathroom. Hope this helps.

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If you are consulting with your local code official I am sure he will want a dry vent but an air admittance valve is legal and will work fine. (you will need an access panel for it though)

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If local codes allow a wet vent a simpler hook up would be to connect the shower to the lavatory drain line where it vwill be wet vented.

Hammer Time

Only vertical wet vents are legal in staes where the IPC has been adopted as the official code. In states that have the UPC as the adopted code both horizontal and vertical wet vents are accepted. Other codes recognize wet venting but each apply different conditions. Both vertical and horizontal wet vents can be complicated as there are restrictions on distance, sizing, proximity to vertical stack etc. I would not recommend that an ameteur attempt a wet vent under a slab where a likely result would be complications at best - -failure at worst.

wrong
I use ipc
I do it all the time and pass inpections I do vertical and horizontal there was a/ an new section added in the 2003 vs. the 2000 ipc

1.5" pipe = 3ft
2" = 6ft
3" =10ft i think
4" = 16 ft I think

still if not cut and dry it can get complicated

Horizontal wet venting is NOT legal in the 2003 IPC- -You are thinking of combination waste and vent which is very similar to a horizontal wet vent but must be connected at least 10 pipe diameters downstream or 3 diameters upstream of any vertical stack and must also have a dry vent somewhere on the combination portion.

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Originally Posted by speedball1

If local codes allow a wet vent a simpler hook up would be to connect the shower to the lavatory drain line where it will be wet vented.

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I don't think venting is going to be a problem. There's another powder room above this one, a full bath above that, and a chase to the attic. So I expect to run my dry vent up to the attic, or at least as far as code requires before tying into an existing vent.

What do you think about putting the drain in the wet wall instead of the floor beneath the shower? I've never seen it done that way, but what would be the problem?

Think of it as the shower pan extending under a horizontal slot in the wall, and then the drain with a P-trap hidden inside the wet wall.

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Originally Posted by MJ85491

The right way is the best way. Breaking concrete is hard work and messy but fairly cheap to replace and easy to finish over with tile or other flooring. ... If you do it right you will always be proud of your decision- - but if you go cheap you will regret it every time you walk in the bathroom. hope this helps.

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Can't I skip the hard messy part and be proud of my innovative solution instead? :)

Sounds interesting. I guess you could try an innovative solution like the one you mentioned. Consult with your code official and if he or she endorses it I guess it is worth a try. Worst case scenario you postphone the messy part until later if you have a problem. Either way you should be proud of your willingness to tackle a difficult project.

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Is there any sort of device I could put in the wet-wall that would substitute for a P-trap?

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It seams to me that to achieve that would involve a running trap or a elbo downturned into a "P" trap ,(see image) . Like MJ I am impressed with your novel way to drain the shower. I've never seen it done that way but if the floor slopes to the drain I can see no reason that it won't fly.