Leak In showing on basement wall

[Mike Mazzla]

I noticed a leak on my basement wall that seems to be happening when I run my shower on the 2nd floor of my house . The wall in the basement is sort of recessed pushed outward to accomodate a largeish white pipe that goes behind it that was put in when I dormered my house 10 years ago and added the 2nd floor bathrooms. There is no indication of a leak in my upstairs bathroom, nor on the wall or ceilings on the 1st floor under the 2nd floor bathroom.

Do you think it is safe to assume that the leak is coming from that pipe behind the basement wall ( the wall at that part juts out to accommodate the pipe. Would it make sense to check behind that first before anything else? Im hoping that it is a simple leak in the white pipe behind the basement wall.

Thoughts? Thanks folks!!

 

[Jadnashua]

Gravity will move water potentially a long ways, so it's hard to say where the leak really is. Since it seems to be occurring when you run a shower, I'd probably start up there. If you get yourself a drain plug, you could fill up the shower and let it sit to see if the level drops. Note, though, that depending on how it is built, some will potentially soak into the structure above the liner that doesn't actually indicate a leak, but it should stabilize and never go down (except for evaporation) after it reaches equilibrium. You could take the trim off of the shower valve and try to look behind the wall there to see if any of the supply pipes are leaking. Carefully check the room outside of the shower for evidence of water - blistering paint, discolorations, etc. You might cut a section out of the wall on the back side (if you're lucky, it's in a closet and easier to patch) to check or moisture. If you have, or can borrow or rent, an inspection camera (one with a fiber-optic cable), you might be able to probe around and isolate the problem.

If you've had lots of rain lately, it could just be rain water leaking past the vent pipe's roof seal, and is a roofing problem. That would only happen while it is raining, and maybe a short time after, though, not all of the time you used the shower.

It happens that sometimes, people forget to add the cement on a joint in the drain pipes! Over time, with the expansion/contraction of the pipes due to thermal effects, it could have backed out enough to leak. Or, if it rubbed on a sharp point (a nail or screw), it could eventually wear a hole. Putting up a wall anchor for say a picture could have messed things up...lots of reasons, and none is more likely than the other.

Some statistics I read one time said that 70-80% of the showers built in the USA are not built according to industry standards, so it's not unusual for one to fail, unfortunately. Sometimes, that takes awhile to show up.

 

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[Mike Mazzla]

Thanks...the only blistering paint I see is in the basement wall..nowhere else, and I know there is a pipe right there because that is where the wall juts out at the top to accommodate the pipe that had to be put there. I thought it would be easier to check that first before playing around with the wall etc around the shower lol. ( wishful thinking also)

behind the shower wall is my bathroom linen closet and there is no evidence of any leak there or in the bathroom directly underneath my bathroom.

at the very least I thought if I open the wall in the basement I could at least see if the leak is right there or if it is streaming down the wall or pipe. does that make sense?

 

[Jadnashua]

YEs, take the easy path first, you might get lucky.

 

[Dana]

If the leak appears near the wall-inset for the drain stack (the fat pipe in the outer wall) the leak is probably the shower drain, somewhere near where it ties into the stack. Since it's not staining any of the ceilings below it's likely to be either near the wall, or right at the drain/stack connection in that stack chase.

If you run water continuously for 5-10 minutes in the sink up there does it appear to leak, or is it only when running the shower?