Trying To Find Source Of Plumbing Water Leak

[JIMMIEM]

I'm trying to find the source of a house plumbing water leak. The corner wall diagonally behind a toilet has peeling paint and feels damp just above the baseboard. This is on the first floor of a 2 story house. There is a full bathroom on the floor above, and the toilet flange 'seems' to be centered over the first floor bathroom's wall that has the dampness. The first and second floor walls that the toilets are against are inside walls and do not line up with each other. Does it make sense and is it legit to have the second floor's toilet flange centered over the first floor wall's top plate? The second floor bathroom's tub is on the far side of the room and doesn't get used. The sink is on the same wall as the toilet and all looks well under it.
I'm guessing either a supply pipe inside the wall or the second floor toilet's wax seal.
Any tips on figuring this out? My current plan is to cut a hole in the first floor wall at the damp area and use an inspection camera to look inside the wall.

 

[Mr_David]

don't cut yet!

pictures help. Those camera don't revile much.
Wax seal leaks often start showing damage on ceiling directly below it.
lot of factors come into play. biggest culprit is tub drain overflow gaskets.

 

[JIMMIEM]

don't cut yet!

pictures help. Those camera don't revile much.
Wax seal leaks often start showing damage on ceiling directly below it.
lot of factors come into play. biggest culprit is tub drain overflow gaskets.

The only thing the picture would show is some dampness just above the baseboard diagonally behind the toilet in the first floor bathroom. There is a bathroom above this on the second floor. The toilet on the second floor is in the vicinity of the first floor toilet but the walls do not line up. From my measurements, the second floor toilet bolts seem to line up with the center of the first floor's wall. I am curious if this is a legit installation i.e. toilet flange centered over the center of a lower wall? If this is the case then a leaky 2nd floor wax ring could leak inside the first floor wall instead of showing up as ceiling stains. Does my logic make sense? That's why I figure I would look inside the wall to see if the culprit is the second floor toilet or something else. FWIW I had a 25 year old copper pipe spring a pin hole leak.....looked like corrosion (flux) was the cause.

 

[JIMMIEM]

2nd floor Tub/shower are on the wall opposite the toilet and haven't been used in several years. The first floor wet spot feels dry today. The roof stack vent comes down through the wall that was wet. Could a leak around the stack flange/boot be the culprit? Hasn't rained in a while. Will check the wall periodically, flush the 2nd floor toilet periodically, and check the vent pipe in the attic next time it rains. Any other suggestions? Thank You.
A picture would only show peeling paint on the wall diagonally behind the first floor toilet. No stains on the first floor ceiling, no water on the floor around the second floor toilet. No other pipes, plumbing or heating, run down the wall with the wet spot. Only pipe in the 'wet' wall is the waste pipe from the second floor.

 

[Mr_David]

Cut it open yet? Did you figure it out?

 

[JIMMIEM]

Cut it open yet? Did you figure it out?

When I went to cut a hole the section of wall that had been wet was totally dry. Had some rain but the vent stack that runs up through the attic and through the roof didn't show any signs of a water leak. Next step is to flush the second floor toilet a lot and see if this is it. Stay tuned.

 

[plumberscott]

You can do a peppermint test

 

[plumberscott]

Get about 1/2 of cup of peppermint oil from a local store.. tape up all the bath tub vents and the fresh air vent outside. Dump the peppermint oil down the vent stack and dump 3 gallons of hot water down the vent stack too. Then cap it.. go inside and start smelling for it.. you'll find which room it is fast

 

[JIMMIEM]

Get about 1/2 of cup of peppermint oil from a local store.. tape up all the bath tub vents and the fresh air vent outside. Dump the peppermint oil down the vent stack and dump 3 gallons of hot water down the vent stack too. Then cap it.. go inside and start smelling for it.. you'll find which room it is fast

Are you being serious about this test?

 

[plumberscott]

Yes I do it all the time on the commercial plumbing jobs I do.. the city plumbing inspector requires it

 

[plumberscott]

Google its, it works great! Let me know if you do it... u can thank me later... hope it helps

 

[JIMMIEM]

Google its, it works great! Let me know if you do it... u can thank me later... hope it helps

I Googled it and found several blogs. Thank you....always good to learn something new.
Should all the drains and overflows (sinks and tubs) be closed/plugged prior to pouring the peppermint and hot water into the roof vent pipe?

 

[plumberscott]

Nope just put some water down all the traps.. that will keep the seal nice.

 

[JIMMIEM]

Nope just put some water down all the traps.. that will keep the seal nice.

Thank You!!!

 

[CT-18]

When I have done them in existing structure I cut the vent in the attic and did it there. It is easier than trying to get on the roof.

 

[JIMMIEM]

When I have done them in existing structure I cut the vent in the attic and did it there. It is easier than trying to get on the roof.

Cutting the vent in the attic would be a lot easier than climbing on the roof. How do you patch the cut vent?

 

[frodo]

with a coupling