New basement bathroom w/ shower installation

Hello all,

First off thanks for any time you spend helping me to understand the finer points of the plumbing world behind the walls and under the floors. I have done some small repairs to the standard house hold P-traps and copper work but I have hired a contractor to take care of the installation of all plumbing work (including the shower kit) in the basement bathroom I recently framed.

The model of the shower kit can be found at the link below:

http://www.sterlingplumbing.com/bath...d=1214100131-0


I will get some pictures and post up if needed but I hope my words can describe with enough detail the problems that the plumber is telling me. He says that the type of shower kit that I have will require to break-up the concrete around the preexisting rough-in. The main issue is that the foundation floor is flat around the rough-in and the drain for the shower kit sits neatly flush with the floor. The drain the plumber bought and showed me has ~1/2" of clearance required underneath the shower kit to work properly.

Just to clarify, the rough-in is a 2" PVC pipe about 10" above the basement foundation and capped. I have done some reading and will test when I get home to see if a P-trap was installed by poring water into it. He is unsure if the rough-in was for a shower or tub; which concerns me since in 10 minutes of reading I found that a typical rough-in for a tub is 1.5" drain and a shower is 2".

Anyway, any advise aside from getting a new plumber would be extremely helpful. Links to the correct type of drain or what needs to be done to make the shower kit I have work with the already existing rough-in would go a long way in getting this complete. The framing around the shower kit is pretty good if I say so myself and I've already had the base sitting in the spot with the existing rough-in going directly up inside the drain hole. Now I just need to figure out how to get water down it!


Thank you again for the time and expertise that you share.

It is normal for a prefab shower pan drain to require an oversized hole around the pipe to provide clearance for the drain. So yes, if the concrete is poured up tight to the pipe, it will need to be cut/chipped/broken out so the drain body fits under the shower pan. If you are lucky, the concrete around the stub is not very thick.

If the drain is 2", it wouldn't really matter what it was originally roughed in for. 2" is the minimum size that should ever be installed under a slab.

You didn't mention anything about a plumbing vent, which is required. Depending on how things are layed out, the 2" pipe you are looking at could very well be the vent connection for the water closet, or the entire bath group.

I understand that my knowledge is limited so to ask the stupid question, what is the difference between the pre-existing rough-in drains for the vanity/shower/toilet and a plumbing vent? There were only 3 setup PVC pipes, a 1.5" drain connection to an existing drain from the upstairs, one ~4" drain in the foundation for the toilet and the 2" which I thought was for a shower drain.

The plumber has not mentioned any issues above and beyond what I have already included above and after reading and talking with a guy at a local plumbing store I have found exactly the information you provided. Good to know that I'm not completely being taken for a ride here.

Thanks again for the feedback!

With minor execptions under certain conditions, ALL plumbing waste traps need to have a vent going up and out to the atmosphere. This prevents waste flow from one fixture from suctioning the water from the trap of others on the same line. Another pertinent rule for a line - once a line becomes a waste line, it cannot be a vent. Yet another, while most of the time, the vents from multiple fixtures can be joined together, there are specific rules about where and how that can be done. A plumber goes to school or works as an apprentice many years before he's competant to do plumbing...a DIY'er can easily make mistakes without knowing it and not realizing the consequences.

You have never mentioned anything about a lavatory drain. If the basement was roughed for a water closet, it most likely would have also been roughed for the lav.

The problem with a house that has a pre-existing basement bath rough-in is that only the plumber who installed it knows what was intended.