Can someone help me decipher this picture? When I had the house built, the builder roughed in a bathroom for later use. The pipes in this picture are

  1. A 2" pipe, possible a vent with a T connector (facing the wrong way) already on it?
  2. A pipe with a cap. Cap measures 4.5". Maybe for toilet?
  3. A huge pipe with a cap. Cap measures 6.25". Maybe for shower drain?
  4. A pipe with a cap. Cap measures 2.5". Maybe Sink drain? Seems really close to #3.

number 1 looks like it's capped and not a clean out, which leads me to believe it was a vent and that it seems like the adapter is facing the wrong way. Is there an easy way to turn it the right way?

enter image description here

3 Answers 3


I ended up contacting the plumbing company that did the rough in. They said:

1-Drain and vent for basement sink

2-Toilet rough-in

3-Backwater Valve

4-Tub Drain


Here is my best guess. #2 is a shower drain. The #1 pipe is the vent for the shower. The tee is to connect the lavatory trap arm, making the pipe between the tee and the shower trap arm (below slab) a wet vent. Wet vents are allow only in certain situations, this is one of them. #3 is the toilet drain. #4 is most likely a vent for the toilet, unless you know of another pipe within 7 feet of the toilet that may be a vent. #1 is too far to vent the toilet. If it is a vent, it needs to be carried up and tied into the main vent system somehow.

You could also wet vent a lavatory through the toilet vent if that location is better than the #1 pipe. Removing the caps and determining which direction the elbows below turn would be useful information in corroborating my guesses. Or if they are not elbows but tees or wyes, though it may be impossible to tell the difference. Also if any to the elbows appear to be a 45 degree bend instead of the usual 90 degree. If #2 is a shower, there should be a trap below that holds water, as opposed to an elbow that does not hold water. Tub, shower, and floor drains are the only fixtures that have traps below the floor level, so the existence of a trap is an important clue.


/#2 = Shower

/#3 = toilet

/#4 = sink

/#1 = vent - most new home rough-ins include no venting in basement because this is usually very easy to integrate. You got one. You can use this to vent everything up to main stack.

Your basement has a very very common configuration. #4 is supposed to be in wall. Putting a wall there would given you the right spacing for a toilet being near wall. Showers are very hard to rough-in before knowing what type of tub or pan you get. That is what I would be most worried about. Only thing a little odd is that sink drain/toilet are so far from your outer wall.

  • So if I understand correctly, there'd be a wall running parallel to the silver insulation that'd be about 1' away and incorporating #4, and that the toilet would face from the right to the left? It seems really odd to be that far out? Maybe for easy access??? So would the vent from #4 go to #1? Isn't the connector A) facing the wrong way (left to right) and B) sloping down instead of up? I haven't looked at what it takes to put a shower in yet. I assume it has to be right over #2? Seems like the drain would be really close to the wall. Commented Aug 13, 2013 at 13:52
  • Yea I guess on the wall. You know you have the pipes in there. Don't be afraid to take a jackhammer or sledge hammer to the area and put the pipes where you want them. This isn't hard to accomplish and is DIY. 1B- your exhaust doesn't drain. As long as #1 leads to a non draining part of your main stack you are good to go. 1A- cut it out and put it in the way you want. #2 - this is always the tricky part of any bathroom - lots are based on shower location. I would pick out your shower base and build from there - there are good plumbers who can custom cement you a base too.
    – DMoore
    Commented Aug 13, 2013 at 15:01

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