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shamrock_94 07-11-2008 07:50 PM

Bathroom rough in
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The builder of my house roughed in a 3 piece bathroom in the basement. I have two issues since I did not see how the work was done before the concrete was poured. Is there any way to tell which 2" pipe is for the tub/shower and which is for the sink? top right and bottom left side of Pic#1. and secondly, if the three fixtures were already vented. Pic#2 the 3" PVC on the right is the waste from the bathroom one floor above. The 3.25" Thinwall PVC on the left, I believe is the vent for the plumbing in Pic #1. Does this sound correct?

Alan 07-11-2008 08:25 PM

normally the drain for the tub shower is 1-1/2" and it should be travelling horizontally, not vertically, and into a hole in the concrete that is filled only with gravel. It's hard to say which is which..... don't you have some sort of plan that would show you?

Marlin 07-12-2008 06:32 AM

Tub and shower wastes are required to be 2" here. Even if the code only called for 1.5" I'd do a 2" rough for a future bathroom. That way if the code changes before the bathroom is installed you aren't re-roughing it.

Keep in mind the information below is a guess, do not take is as a fact.
The sink seems to be next to the toilet. This would allow the toilet to be wet vented through the sink. It also explains why the sink is roughed in 2" rather than 1 1/2". The tub is typically in the back of the bathroom. It seems like if you installed walls and a door the area by the stairs would be the back. The tub rough is very strange though. It shouldn't be sticking up like that, their should be a small box with no cement in it around the waste.

Now that I've guessed you need to figure out which waste line has a trap. The right way to do it is with a sewer camera. One of those Ridgid see snakes would probably do it as well. The ghetto way is to dump some water down both 2" lines. Wait a day then stick a rag on a coat hanger or something down each pipe. Just make very very sure that whatever you stick down the pipe isn't going to get stuck or you'll be chopping concrete. The one that comes back wet has a trap.

Even better, can you contact the builder. They can tell you exactly what you have.

BillyD 07-12-2008 08:14 AM

Also you may just try smelling the pipes and see which has the trap. They do not look to be capped. If they are not and you don't have sewer odors they may both have traps.

shamrock_94 07-12-2008 08:55 AM

both 2" pipes are "capped" not a permanent cap, but just a flat plastic cap to keep the gasses in. btw by now any water in the traps would be dried up., as the house is 5 yrs old.

Marlin brings up another concern I had. Without the box you mentioned how would I hook up a tub drain w/ overflow? Is it possible that the builder skimmed over the small box when the basement was poured? I haven't had the courage to start pounding to find out.

One more thought isn't is strange that the drain for the "tub" (by the stairs) is on the opposite side from the sink and WC? Most baths I have seem have all the waste plumbing on the same side of the room.

Alan 07-12-2008 11:12 AM


Originally Posted by shamrock_94 (Post 138366)
One more thought isn't is strange that the drain for the "tub" (by the stairs) is on the opposite side from the sink and WC? Most baths I have seem have all the waste plumbing on the same side of the room.

Most architects draw houses that way because it's "easier". We always switch it, so that if you're lying in the tub, you're not staring at the toilet. It isn't that much more difficult in most cases.

mstplumber 07-12-2008 10:33 PM

OK, here's my 2 cents. It looks like Marlin is right. The 2" to the left of the toilet is the lavatory stack, which probably also serves as the wet vent for the entire bathroom group. The 2" nest to the stairs is the tub drain. Many codes allow no pipes smaller that 2" under a slab, even if a smaller pipe would work. The most likely reason it is not on the same wall as the toilet is because that wall is a concrete foundation wall and that makes it a little harder to access and work with the tub valve. Since the maximum distance a 2" trap can be from a vent is 8' (6' in some codes), if there isn't another pipe within that distance you can be pretty sure the other 2" vents both the tub and toilet.

The concrete should be boxed out around the tub drain, but concrete crews are notorious for removing these boxes and "forgetting" to put them back. If you are lucky you may find that the box is there and just skimmed over but don't hold your breath. An easy way to check for a trap to pour a little water into the pipe and look down it with a flashlight. If you see water it is either a trap or the line is stopped up. Since you will have to break the concrete around the pipe anyway to install a tub or shower, just make sure there is a trap installed.

As for the "3.25" Thinwall", I don't think it is a vent for the bathroom, I think the 2" in the first picture is serving as a wet vent for all 3 fixtures. This is a very common installation and is just fine. If the pipe in question is really "Thinwall". or something other than Schedule 40 wall thickness, it shouldn't be a part of the Plumbing system. It is possible it is a Radon vent, many homes have them in some areas of the country. Once again, you can cut the pipe, pour in some water and look inside. If it is a Radon vent it might not drain, although a properly installed Radon system will have a lot of pipe or gravel filled trenches under the slab and the water should drain out. If you can't figure out what it is, just leave it alone.

Having said all this, a sewer camera would take all the guesswork out of it, but that will probably cost you at least a couple of hundred bucks.

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