On Oct 13, 10:06*am, dpb wrote:
DerbyDad03 wrote:

...

- New problem, started about a week ago.
- The last modification to the system was a replacement fill valve in
a toilet, but this was many months ago, with many months of no noise.
- Yes, I have a pressure reducing valve.
- No, I have not checked the pressure.

I think that isolating the toilets should be my first (and easiest!)
step.

That can find if it is one of them, obviously. *I've had issues w/ the
reducing valve failing in full open spot. *Pressure itself isn't the
direct cause of hammer, of course, but higher pressure could be the root
cause of the cycling of a toilet valve. *Or, it could be the reducing
valve spring itself chattering as it cycles.

--

Any chance it could be the meter itself? When things are working fine,
I can always hear a slight ticking at the meter. The frequency of the
ticks is close to the frequency of the thumps. I don't know if there
are digital water meters for homes, but mine is analog in that that
there is a large dial for gallons and a little red triangle that spins
when the water flows.

One thing that I have noticed for many years is that if I turn off a
fixture and watch the triangle, I can both hear the flow of water for
a few seconds and the triangle continues to spin, slowly, as if the
pipes are "refilling", perhaps building back up to pressure. I wonder
if the meter itself is chattering, and thereby causing the thumping.

I'll call the town and see what they have to say.