Diagnosing a possible drain leak
 

A few months ago I noticed a small water stain appearing where a
plaster crown molding meets the ceiling. Recently I noticed a
dripping noise after I shut off a sink in a bathroom that's more or
less above the stain. I might not have noticed it sooner because
there's usually a lot of noise from the bathroom vent fan.

Before I call a plumber or have the ceiling or wall ripped open, I'd
like to find out if the drip actually indicates a leak, and not just
normal water draining through the drain pipe. If I run the sink for
10 seconds, then shut it off, the dripping starts about 15 seconds
later, and continues for about another 15 seconds, at a rate of about
3 drips per second. I can hear it from the bathroom as well as from
the downstairs room. The plumbing is about 20 years old, in a house
that's much older.

Are there any tricks to find out what's going on?

Jimmy

Diagnosing a possible drain leak
 

Diagnosing a possible drain leak
 

Diagnosing a possible drain leak
 

On Sep 23, 4:57 pm, dpb wrote:
The water stain indicates a leak.

Whether it's actually the drips hitting the ceiling or inside the drain
is of little consequence; the leak needs fixing.

The thing is the dark area on the ceiling is so small and slow-growing
that I'm not even sure it's a leak. It's maybe 6 inches long and a
quarter inch wide, along the edge where the ceiling meets the molding.

As another poster said, investigate for dampness in the plaster and the
ceiling area. If it is drain rather than supply, not using the suspect
sink for a while should allow it to dry completely whereas a supply line
leak would continue.

How long should I avoid using the sink to wait for it to dry?

I think the drain pipes are PVC, but if they're copper, does that mean
a dripping noise definitely indicates a leak?

Jimmy

Diagnosing a possible drain leak