Richard Fangnail wrote:
In my apt the tapping noise can come from my ceiling or one of the
walls. When the tapping got bad a few weeks ago, it got bad in both
places at once. Why would that happen, if the problem is due to the
pipes rubbing against the holders?

Sometimes the noise is in one of the two places and sometimes it's in
both.

A slight tapping noise is not imo likely to be rubbing per se but more
likely thermal contraction/expansion--very similar to the occasional
pop/creak heard in a house's siding when warms up in sun on a cold day.

I had one house w/ a very long horizontal drain run from a sink -- in
it, there was a sound that could be described as a tap that was actually
a drip internally until that drain line finally finished emptying.

Someone mentioned a pressure regulator. What is that exactly, and how
might it cause the tapping problem?

It would be a pressure-reducing valve and is a spring-loaded valve that
could be installed to reduce house pressure from the higher-pressure
distribution system. Normally, if these get noisy they make a more
distinct sound than I would describe as a tap, but I suppose if it were
buried in a wall or a ceiling somewhere it could be muffled.

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