Water dripping noise when emptying the bath

sbird90

Hey all

wondering if anyone knows what the dripping noise is when I empty the bath. It sounds like it’s coming from the pipes around/behind the toilet(in the wall possibly) however whats strange is if I stop the bath emptying by covering the plug, let a little water drain out slowly for a couple of seconds, then pull the plug again, no dripping noise at all! If it was a leak I’d presume it would drip regardless of stop and starting the water flow? No damp patches etc that I can see on the ceiling below. Always stops every single time I stop draining and then let it flow again. 

JIL

Is it the air admittance valve on the down pipe?  I hear a tapping noise when I empty the bath, it does sound a bit like dripping.

I'm sure if you do a Google search it will explain it.

Another_Level

Sounds like thermal expansion of the waste pipe while warmed water is flowing through the waste pipe, annoying but it can happen when hot water pipes are touching something solid.

It's fixable but needs some detective work