When either of our two toilets is flushed,
we get a jackhammer oscillation in the supply
line until the tank is filled. Turning on an
additional faucet while the toilet tank
is filling increases the frequency of the
oscillation, so it seems to be related to
the volume of water flowing, but it occurs
only when a toilet is involved. It can't be
invoked by turning on two faucets, for
example. This plumbing has been in place
for 23 years, but this condition didn't
exist until a couple of years ago.
What's going on?

--
Charles Packer
http://cpacker.org/whatnews
mailboxATcpacker.org