Question: I have a
small water leak inside a wall. There are water supply lines and a
waste line inside the wall that lead to an upstairs bathroom. Near the
baseboard there are paint bubbles and moisture so there must be a leak
on the other side of the wall. One side of the wall is drywall and the
other side is plaster. The drywall side is completely dry, but it is
probably the easiest way to cut into the wall partition to see what I am
dealing with. How would you recommend I go about opening up a small
portion of the wall to see what is the source of the leak is?
Answer: First. it is
important to remember that where a leak is visible is not necessarily where
the leak is originating from.
This said, I would take a careful
look in the upstairs bathroom first before cutting any holes in your walls.
The likely source of the water leak is probably associated with the upstairs
toilet, bathtub or sink. Carefully check these bathroom fixtures for leaks
before contemplating cutting into the drywall/plaster. Specifically check
around the valves and fittings to make sure they are not leaking. Also, take
a careful look around the toilet, as the problem may be associated with a
faulty toilet wax ring. If it is a faulty toilet wax ring, you potentially
may see water leaking out from around the base of the toilet. If this is the
case, you can turn off the toilet supply line and replace the toilet wax
If no leaks are observed, then
one simple test you can perform is to leave the faucets off in the upstairs
bathroom for awhile and see if the moisture problem dries up. If it does,
then the water leak is most likely associated with a waste line or trap. If
it was a supply line leak, then the water problem would persist even if the
faucets were not used.
If there are no leaks around the
supply lines in the upstairs bathroom and the problem dries up when you do
not use the upstairs bathroom for a day or so, then yes you will probably
need to cut into the drywall.
However, just remember the leak
is probably higher up, e.g. in the tub or toilet drain trap area for
example. Ultimately you may end up having to actually cut into the ceiling
to get under a drain trap, as this is most likely the leaking area.
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If you are still inclined to
punch a hole in the wall to observe the source of the leak, I would
certainly go in the drywall side versus the plaster side. However, you may
want to go into the drywall near the ceiling. Again, you will probably wind
up having to cut into the ceiling to actually get to the problem area. If
you can identify the problem bathroom fixture ahead of time, e.g. such as
the bathroom tub you may just want to skip cutting a hole in the wall and go
right for the ceiling, underneath the tub.
Additional Home Plumbing Resources
Bathroom Fixtures from Amazon.com