Alternatively, would any type of partial pipe clog cause a temporary dripping sound? In fact, can anyone think of a reasonable cause for a drip sound that starts about 30-60 seconds into a shower and only lasts 10 - 20 seconds, then stops - all while the water is running? I was thinking perhaps the start might be from when someone steps into the tub, but I can recreate the sound by flushing the toilet while the shower is running. I haven't yet gotten into the tub while some someone is listening downstairs. Any ideas or new things to check would be welcome.
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I have an upstairs bath creating a dripping noise in the wall which is baffling me. There is one scenario (only one been able to identify so far) which creates the drip noise. Shower/tub water is turned on, and the spout diverter is pulled up to initiate the shower. Then the toilet in the same bath is used (shower still running). I hear a drip - drip - drip sound, lasting maybe 20 seconds or so, then stops. No signs of water leaking out in wall or ceiling (although we have had problems with the bathtub overflow leaking when in bathtub overfills - not the situation here). I can hear the sound clearly at the 90deg bend of the PVC pipe in the basement pretty much underneath the 2nd story bath. In fact the sound there seems to be drip-drip-drip, then eventually a gush of water, then eventually I can feel the pipe warm up as the hot shower water warms it. The pipe and area around the pipe in the basement seems dry.

Any ideas on the cause or things to check? This just started a few weeks ago. Would a partly clog pipe cause this? The drip sound always stops well before the shower is finished. Thank you.

Not an answer - just pinging this to see if anyone has any ideas of cause or even what to check (without just tearing a big hole in the wall to see if I can see anything leaking). I don't have any visible signs of water. And the dripping sound doesn't persist for the entire shower. It can be reliably created when flushing the toilet while the shower is running (in the same bathroom) - but either by itself doesn't generally create the sound.

The sound of a pipe expanding, due to hot water, and sliding againist a stud can sound just like a drip. Are your pipes copper, PVC, PEX or what?

The drain pipes are PVC, the water feeds are copper. It may be pipe expansion. It's just baffling in that the sound just began about six months ago (been in the house for several years).