I am trying to guess if it is possible to relocate the blue pipe to the right of the vertical one This is the basement, concrete slab. I can't quite figure out the plumbing for the main drain and I am not sure if I will break the concrete above it. It is essential for me before starting the work, to know that what I want is possible and there is enough room to install the horizontal blue pipe above the horizontal grey drain

enter image description here

I am tying to move the yellow pipe in the picture below in the position where the vertical red pipe is The red pipe is what I am planning to install, the yellow is what I am planning to remove enter image description here

Suggestion by ecnerwal enter image description here

Here are the real distances for the existing pipes in the basement 16" for the fist to the left vertical black line in the picture (the sink I am relocation and whose pipes are discussed here as a possible replacement for the lower section of the yellow pipe) 4' for the second one. I also highlighted the contour of what appears to be where the opened the floor to install these to the left you can see the clean outs of the soil stack and the dry vent (1.5") this is the yellow pipe I am trying to relocate enter image description here

And here is the updated Sketchup model including Ecnerwal's changes The bath tub will rotate 90 degrees counter clock wise and will be replaced by a shower pan The sink will move to the south of the picture in the corner where the bath tub ends enter image description here

  • Missing a picture with red and yellow pipes? You might get a little bit of insight with one of those "drain cameras" (I think you can rent them? Or hire an operator with one for an hour or so.) But it may not be easy to really get a sense of the layout even then.
    – Ecnerwal
    Aug 16 '20 at 0:03
  • I don't see any yellow or red pipes... and you shouldn't assume anything under the slab unless you get it all traced out.
    – JACK
    Aug 16 '20 at 0:04
  • sorry I just added the picture let me put it this way ..I am not worried about where the main drain is I am worried about the way the WC and the drain from shower and sike and the vent are stacked there/ The picture is a representation of my wishful thinking. If so will that comply with the code?
    – MiniMe
    Aug 16 '20 at 0:26
  • If pipes are iron, a metal detector might read through the slab. Aug 16 '20 at 1:31
  • Having to repair plumbing under a slab I found the best way to locate the pipe mid slab is to have a person tap on the pipe with a hammer while you use a dowel on the slab to your ear move around to the loudest point you can track the pipes very accurately using this method sometimes how they were run was for cheap others for access.
    – Ed Beal
    Aug 16 '20 at 1:36

That should work if your wishful thinking is correct, though you might find it more practical to leave the stack alone and re-route the yellow vent around to where the red pipe is, rather than tearing up the stack to put the vent connection on the opposite side. Messing with the bottom of a stack is not trivial.

IF the pipes to the sink are big enough (and probably not if they were not intended for this) you could also route an above-the-slab dry vent from the sink and the sink drain line would wet-vent the rest, but if it's not big enough that won't fly.

Unclear from your comment, but if the place you "need to move" the yellow pipe is the upper floor, you can run it (properly sloped back to the drain) "horizontal" once it is 6" above the flood level of the highest fixture in the floor it serves (the basement.) Not the highest fixture it serves, the highest fixture on the floor it serves. So you could make the move (if the upper floor is the area of concern) without getting into the concrete.

  • The horizontal segment for the existing sink in the basement has 1.5" and I could change it but the yellow pipe is 1.5" too. Just to be clear thw red pipe is not there, it shows the new position I was considering for the yellow pipe. I did not think about removing it and trying to us the existing sink pipe as wet vent. Isnt this pipe too far up to help the toilet with ventibg?
    – MiniMe
    Aug 16 '20 at 2:45
  • The existing sink pipe junction with that horizontal pipe that goes to the tub in less around 1ft away from grey vertical pipe (soil pipe).
    – MiniMe
    Aug 16 '20 at 2:58
  • I added the third picture...is this what you are suggesting ? Build the red pipes as dry vent for the new sink (top left corner of the basement floor) and the existing shower and use the old sink piping to wet vent the toilet ?
    – MiniMe
    Aug 16 '20 at 3:42
  • Note that all the horizontal runs in your latest picture need to be "6 inches above the flood level of the highest fixture." The venting rules are complex and depend on which code applies to your locale - I'm under IPC with a few local changes. I think you'd be fine wet venting if you have 2" pipe for the wet part,- your current setup appears to be a dry vent at minimum size, so I doubt that wet venting at that same size is allowable, but there are a number of overlapping rules about allowable wet venting for bathroom groups...
    – Ecnerwal
    Aug 16 '20 at 11:00
  • my current setup is in the second picture, that is closer to wet vent than dry vent for the basement, the red pipe segments in the third picture are not there, that is what I would do since I am not sure how well the wet vent would work. I am not sure if the current design (yellow pipe in place ony) is OK. I have had no clogs or odors but I never paid attention to the sound the water makes when it goes down the drains in basement. The tub/shower has not P trap! ...I guess that was part of the wet vent plan (took the risk of getting odors but it provided two venting pats for the toilet?
    – MiniMe
    Aug 16 '20 at 12:19

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