water pressure: hammer/reducing valve?

Before reducing you pressure have a dig around you CW system for any ?dead legs? that might have become air filled. These can be a potent cause of mains water hammers.

Tim

Tim+ laid this down on his screen :

Actually I would have expected the opposite - the bubble of air would help buffer the the sudden surge in pressure, when a valve shuts suddenly and the rushing water has nowhere to go.. Which is what causes the hammering noise.

Fit an isolator and half-turn it ? When I redid all our plumbing I fitted isolators as a matter of course anyway.

It might be worth fitting a hammer arrestor, like one of these

Jethro's suggestion is probably better, because it limits the flow to the individual machines, not the whole house. But it may mean a modification to the plumbing.

Jethro_uk <jethro snipped-for-privacy@hotmailbin.com wrote in news:q4e6ua$1o0$ snipped-for-privacy@dont-email.me:

They can be noisy though.

Sometimes hammer can be due the the filler hose being too elastic.

Also some pipes that have dips in their runs or where the clips have failed. Its amazing how much racket just a tiny vibration can cause. I often also think that recent improvements in water pressure generally has exposed bad joints and hence started to reveal leaks in the street etc. Round here at least. Water is a strange thing as it cannot really be compressed but any trapped air of course does! Brian

I'm sure unsupported or insufficiently supported pipe work is the cause but it was fitted by a previous owner and is behind the kitchen units and under floorboards, so I cannot do anything about it until I have a major redecoration.

Thanks, Stephen.

Yes, I've heard that throttling the isolator can cause the flow to be more noisy. I think the problem is that with washing machines and dishwashers, the valve is either open or closed, so it is quite harsh in it's operation; there's no gentle opening or closing of the valve, like you do with a tap.

Thanks, Stephen.