Water hammer

[Johntheo5]

Yeah checked that!

I was just having a play now and I'm wondering if the hammer is coming from the multibloc - you said there's a one way valve in there? Could these make noises?

I have seen posts where replacing them did apparently get rid of the problem but obviously no guarantee.

What vol is the under sink shock arrester?, You say? the 3bar pressure doesn;t change with the mains isolated or not, I would suggest reducing the charge pressure to 2bar as that will act in a better fashion to absorb any shocks.