F wrote:
On 10/10/2009 13:37 Andrew Gabriel wrote:

One possible cause of water hammer is a deadleg with air trapped in it.
Now, a Water Hammer Arrestor is simulating a deadleg with air trapped
in it,
so you might want to see if you have some more real ones on the pipework.

I'm pretty sure there's a horizontal dead-leg (remnant of a water supply
into the garage) and I have long suspected it's the problem but I can't
get into that space to check.

Seems odd that introducing a simulated dead-leg is supposed to cure the
problem...


Changes the resonant frequency of the system.

Andy