I know about water hammer - the loud noise associated with a rapidly
closing valve causing the water to slam inside pipes causing them to
bang. I also know most of the solutions - arrestors, expansion tanks,
securing pipes, draining the pipes, etc.

The water hammer I'm experiencing is different.

- Instead of a single loud bang, I get a rapid fire dull
thump-thump-thump almost like the rat-a-tat-tat-tat of a machine gun.
- They happen when just about any faucet, toilet, shower, appliance,
etc. is turned ON or OFF.
- When a device is turned ON, I'll get 4 or 5 rapid thumps lasting a
second or two.
- When a device is turned OFF (even slowly turning off a faucet) I'll
get anywhere from 20 to 50 rapid thumps lasting 3 - 7 seconds.
- It happens with both hot and cold water, single valve devices or
dual faucet fixtures.
- It happens 85% - 90% percent of the time.
- I have drained the system and refilled it. I thought it helped,
because it didn't happen for a few hours, then it started again. It may
have just been the 15% - 20% of the times when it doesn't happen.

Anybody heard of this type of water hammer?