whats that noise (dripping)

I recently moved into 3 level, 3 bed, 3 bath townhouse (no basement, ground floor foyer). The buildings about 18 years old. There are houses surrounding mine to the left, right and back (have no deck or backyard). I had a home inspection done which revealed some minor problems.
I then started noticing dripping noise at regular intervals, more frequently when I used the tap, sink, bath on the top 2 floors and not so frequently otherwise. But to date (its been 6 months), I havent seen any leaks appearing anywhere. I have had some plumbers come in to fix fixtures, but even they couldnt figure what it was. Its perplexed me no end.
Can anyone advice what it could be.
Thanks.

Drip Drip Drip

could just be the water dripping down the waste stack and splashing on the bottom or at an offset. If you had a cast iron waste stack I would think you couldn't hear it, but I dont know maybe you have a copper waste stack. Have you tried to narrow down the location that you can hear it at? Try to pinpoint where the noise is.

Clayton said:

could just be the water dripping down the waste stack and splashing on the bottom or at an offset. If you had a cast iron waste stack I would think you couldn't hear it, but I dont know maybe you have a copper waste stack. Have you tried to narrow down the location that you can hear it at? Try to pinpoint where the noise is.

Click to expand...

I know for sure (99%) that the supply and drain pipes in the house is copper.
Actually there are a couple of places I hear the noise. One is right besire the washer/dryer above the kitchen and the other walls adjoining the neighbour (maybe he's hearing it too). My main concern is should I be taking any remedial action or doing anything at all about this.

Thanks.

Also

do you have a diagram that explains this,
"could just be the water dripping down the waste stack and splashing on the bottom or at an offset".
I am no plumber, thats why its not easy to understand.
Thanks.

drip

If it has been that long and nothing has shown up as far as leaking water, then your "drip" may just be expansion of the hot water piping as the pipe heats up when you use the faucet.

Thanks

a bunch !!!