In my guest bathroom (which we hardly ever use) I noticed a pulsating
sound coming out of the drain. It's freaky. It's rhythmic, about two
'thuds' per second. I checked under the sink, there's no leak. There
are no exhaust fans running in the house. I don't know if there's
anything else I need to check. Could there be an internal leak
somewhere? It's a hollow sound I dont' know how else to describe it.

wrote:
In my guest bathroom (which we hardly ever use) I noticed a pulsating
sound coming out of the drain. It's freaky. It's rhythmic, about two
'thuds' per second. I checked under the sink, there's no leak. There
are no exhaust fans running in the house. I don't know if there's
anything else I need to check. Could there be an internal leak
somewhere? It's a hollow sound I dont' know how else to describe it.

My guess is the P-trap has dried out, try running the water in the sink for
a minute then listen.

Rich

On Jan 17, 2:53 pm, " wrote:
In my guest bathroom (which we hardly ever use) I noticed a pulsating
sound coming out of the drain. It's freaky. It's rhythmic, about two
'thuds' per second. I checked under the sink, there's no leak. There
are no exhaust fans running in the house. I don't know if there's
anything else I need to check. Could there be an internal leak
somewhere? It's a hollow sound I dont' know how else to describe it.

Does it make the sound when water is draining?
If so it could be a mechanical vent under the sink.
Mechanical vents are used when it is not possible to get a pipe to the
roof.