How to plumb attic half bath lines to existing downstairs bathroom lines

[Coreman73]

Hello,

I am beginning an attic remodel. Part of the addition will be a small half bath. Due to the attic configuration, it's not possible to locate the new half bath directly above the downstairs bathroom but I can probably get to within 6-10' of it.

Would I be still be able to tie in the new attic toilet and sink waste lines to the existing plumbing of the downstairs bathroom? If so what would be the best way to learn how to do this?

I'm wanting to attempt this myself so am really here for pointers. Any help is most appreciated.

The house was built in 2003.

Thanks,
C

 

[Coreman73]

Does anyone know of any great online tutorials that could help me learn about what I'd like to do in my post above?

 

[Sponsor]

 

[hj]

To do it correctly, it is NOT a "first time DIY project", and there is no 'one video fits all" because every installation is different.

 

[Reach4]

Does anyone know of any great online tutorials that could help me learn about what I'd like to do in my post above?

See the diagram in this post: https://terrylove.com/forums/index.php?threads/vent-pipe-and-drainage.62823/#post-465577
Check the links in this post: https://terrylove.com/forums/index.php?threads/water-closet-rough-in-question.61855/#post-458278

 

[Coreman73]

hj, your points are well taken. This is something that will be a ways down the road and I'm obviously not close to being able to do this myself simply from lack of knowledge.

Great information Reach4. Thank you.

A few questions:
1. If I'm running my lines (sink, shower and toilet) from the attic to the 1st floor, do I absolutely have to have them all tie in to a minimum 3" drain line? I don't know what size (3 or 4") my main drain line is.
2. I don't know where my main drain line is exactly but obviously in the slab. If the answer to question 1 is yes then would I likely need to dig up around the slab and tie in to the main drain line?
3. Where would I put my clean out for the attic line system?
4. For this attic bathroom, I likely have enough room that I can position it above either the downstairs bathroom or kitchen. Which one would be preferable?
5. Is there a chance my main drain line is exposed in the wet wall in my kitchen? If so then maybe that's the best choice to go with.

 

[Cacher_Chick]

Unless you know where and how each of the existing fixtures are drained and vented, your new drain will have to be tied in downstream of them.

 

[Coreman73]

My bathroom has two vent pipes. One is 2" and vents both the toilet and sink. The other is 1.5" and vents the shower. The sink and shower are located along an exterior wall. The toilet drains directly into the 3-4" pipe below the slab. I'm guessing the sink drain pipe must tie in to the main drain at some point inside that wall.

My kitchen is vented with one 2" vent pipe. It's drain pipe of course also ties in to the main drain at some point in the wet wall.

Is there no way to determine exactly how the bathroom and kitchen actually tie in to the main drain without tearing out the wall in those areas? I guess I'm just wondering what is typical for a house built in 2003 on a slab. For example, is it common to have the main drain protrude through the slab enough to tie in the sink/toilet/shower drain lines? If not then it sounds like the only way to tie in to this main drain line is to break through the slab.

I wish I had a basement for easy access and visibility.

 

[FullySprinklered]

HJ and Casher are spot-on. I've done a half-dozen attic bathrooms, but always on crawlspace or cellars. It's the toughest remodel work I've done, and am not looking for any more of those. Never done one on a slab, but I can promise double the agony.

 

[Cacher_Chick]

One way to avoid breaking too much of the existing slab is to route a new drain stack down to a location where it can go below grade near the exterior wall nearest the building drain, turning to make the connection outside.

 

[Coreman73]

Cacher_chick, I may explore that option if I can't do what I mention below. Fullysprinklered, you sound like you've got quite a bit of experience doing these type of remodels.

The top plate of the wet wall I'd need to penetrate to run the drain pipe from the attic is a 2x6, which I guess is pretty common. Is it common to run a 3-4" drain pipe through one of those? I don't see any other way to get that pipe down to the slab.

Also, this top plate is located on an exterior wall of the house so the roof pitch is extremely small. There's maybe 3-4 inches before I hit the bottom of the roof. Obviously there's no physical way to get a tool in there to cut a hole in the top plate to help run this pipe. The only option I can see is to remove a small section of the roof above where I'd need to drill so that I can get in there to work. I've chosen this particular top plate location because there is a clean out directly below. It can be accessed about 12" above the slab from the outside wall of the house.

I guess I'm just wanting to see if anyone has any ideas. Is it possible to tie the new drain line to the clean out pipe (looks to be at least 3")? If I could do that then maybe I wouldn't have to bust the slab for access to the main line.