[frazwood]

A bit of background: My wife and I are about to purchase a home (closing date = April 23) that has some 'issues' (don't they all?). The former owner was in the middle of renovating most of the house... specifically, he was in the process of putting in a second bathroom. It looks like he put in the water supply lines but there is virtually no DWV plumbing installed in the second bathroom. Unfortunately, he has passed away and his estate has no knowledge (all of the children live far away) of the status of any of his projects. He has clearly finished much of the renovations -- he generally did very good work.

I have two problems:

Problem#1:

I want to provide drain-waste-vent plumbing to the new/second bathroom. The new bathroom is in a portion of the house that was not part of the original house structure (i.e. it's in an addition that was added at some unknown time). This means that the addition has a crawl space whereas the original house has a basement.

In the basement, there are two possible locations where I could hook in the new drain-waste plumbing. The first hook-up location is to the main stack, which is a 3-inch cast iron pipe. To do this, I would likely need to replace the cast iron stack, which is a lot of work. Also, I would need to drill a hole through the concrete basement wall, which is also a lot of work.

The second access point to the sewer is where the washing machine currently drains. It is currently a 2-inch line, but it looks like I can pull that out of the floor entirely and install a 3-inch PVC pipe. This option would be easier (I wouldn't have to drill a hole through a concrete wall or cut a cast iron pipe) but I am unsure if the plumbing under the house (since I didn't do it) can handle a 3-inch drain line or not. I can run this line through the hole that provides access to the crawl space (hence, no drilling through a concrete wall). My guess is that if the original plumber left a hole in the concrete big enough for a 3inch pipe that it can handle a toilet/sink/shower from a second bathroom (perhaps it was intended for a basement toilet? I'm not sure, so please comment).

Problem#2

I would like to replace the bathtub in the existing bathroom. The tub is gross, old and cheap; the tub surround is also gross and needs to be replaced. This tub currently drains to the main, 3-inch cast iron stack. The plumbing between the tub and the cast iron stack, however, is mainly ABS. If I replace the tub, can I connect PVC to ABS? I'm asking because my DIY plumbing book recommends against using ABS.

Thank you in advance for all comments and helpful suggestions

[Milo Dolezal]

If the previous Owner planned on installing 2nd bathroom then he most likely made a provision for it. Yes, your basement plumbing should be able to handle one more bathroom. You should have at least 3" main sewer pipe which is large enough to accommodate new bathroom.


Question #2: Yes, you can mix PVC and ABS. The only place you have to worry about is the connection between the two material. They sell ABS-to-PVC glue or even better use shielded Fernco coupling.

[speedball1]

Problem #1) Go wiith the easiest way to connect with the house sewer.
Check with the Building Department to see if they allow wet vents. If so run the drainage like this.(see image). Except, substitute 2" for 1 1/2".
Problem#2) Yes! Answered by Milo.
Good luck, Tom

[frazwood]

Thanks guys! Very helpful!