Replacing a tub with a shower stall - drainage question

Here's my situation... I've gutted my bathroom, and want to put it back, more or less with the same fixtures and placement as the old setup (but much nicer of course!). The difficult part is that I wish to replace a tub shower combo with a nice shower stall...

Space isn't an issue, I think I've figured out all the tiling issues, etc. But the existing drain pipe for the tub was a 1 1/2" copper pipe. I've done some searching and reading around here, and from what I gather, it's advisable (and up to code standards) to have a 2" drain for a shower stall.

Now, I have access to the plumbing - it's a second story bath, and there's no subfloor in there at the moment. But I'm not exactly sure what would be required to replace that drain line. I have some photos of what's there currently, since I do not know the terminology to describe it...

Any advise is most appreciated

This is what's left of the tub drain plumbing...


The drain runs across the room, to meet up with the 3" drain that runs vertically in the wall... Here's an overview of that wall.


And here's a closeup of the join. The left fork is the tub drain connection, the right is the toilet drain line. This connection is the one I have no idea what to do with, but suspect would have to be changed.

You are right, you'll have to take that fitting at the stack out and replace it so thatthe shower gets a 2" line. While you are at it, you want the drain to be relocated to the middle of where the shower is going to go. You can use pvc or abs plastic pipe for this if you wish, rather than the copper. How far is that stack from where the center of the new shower will be? On a 2" pipe (I think) it needs to be within 5'. Also, make sure that you can maintain 1/4" per foot slope down from the output of the drain to where it connects to the stack.

If you are going to tile this, consider checking out www.johnbridge.com for tiling help. Also, read up at www.schluter.com on Kerdi and www.wedi.de on Fundo shower systems. They both make great hi-tech tiled showers. You can also make a conventional shower, and the instructions for that can be found over at John Bridge's site as well in their "Liberry".

Thanks for the quick reply!

I ended up at this forum through the ones at John Bridge's place. I'm pretty sold on the Kerdi system

I am well aware that the shower drain should be as close as possible to the middle, but perhaps this picture will show better what I'm up against... The halfway point in the shower would be about 13" past that double floor joist (towards the bottom of the photo). My plan was to move the drain as close as possible to the double joist, but not make any cuts into them.

jadnashua said:

you'll have to take that fitting at the stack out and replace it so that the shower gets a 2" line.

Click to expand...

This is the general gist of what I thought would be required... but what exactly is involved? I am showing my lack of plumbing knowledge here, but I've never done much more than simple PVC connections.

The fitting at the stack is roughly level of with the bottom of the floor joists and while the top is accessible, the bottom of the fitting is not really. I assume that the copper stack would need to be cut? how is this done (special saw blade)? and then what type of fitting would I put back into the stack?

Another option?

I just had another thought about this last night...

The stack running up and down the wall has a 3" OD. Thats the same size as the drain running from the toilet. Is there a way I could cap off the 1 1/2" pipe near the stack and then T into the toilet drain line instead?

I have a copy of the Michigan code book, but I'm really not sure where to look to determine if that type of thing would meet code or is even advisable...

Thanks again!
-Erica

As I understand it, the drain needs to be vented prior to meeting up with the stack; if you tap into the toilet drain line, it would not meet that condition. Now, would it work, probaby, especially if it was right near the stack. Better to get a reading from one of the pros...

hi Erica

what Jim said.

i'll add this: Show us your intended layout. That'll help ensure the advice you receive is appropriate to your design. Specifically, where is you shower-to-be going to line up with your interesting joist / board subfloor?

Have you consulted a Master plumber about venting if you branch into a 3" toilet waste pipe?

Without meaning to cause confusion -- i'll add some tidbits. These are not recommendations, just information.
1.) A 1.5" diameter drain also carries enough water to do the necessary function of draining a shower pan. It just isn't "Code" anymore, ever since that change was implemented to the code book.
2.) A shower drain can also be located at the edge of the shower floor, and that looks good when you design it to be in a long drain channel along one wall. Sometimes called a scupper drain. This means your shower floor is flat and it slopes towards the drain wall. Takes a little more height than a cone-shaped floor. If you don't want to cut joists, this is one option to consider.
3.) How much a drain pipe can carry depends on the length of the pipe, so the above option is even more meaningful when you consider both 1.) and 2.) together. A short run of 1.5" pipe, with teh existing fitting left in place, then becomes one option to consider.

Q: What do you know about the subfloor shown in your last posted picture? There are joists in one area (not the old tub area) that look to be about 16" apart. Under the old tub area it's built differently, so I'll let you be the first to describe it.

What you decide to do should not be based solely on what you have read here. More reflection, checking and double-checking all other options is recommended.

David