water pressure: hammer/reducing valve?

[Stephen]

Hello,

I have some water hammer caused by the washing machine and dishwasher. Should I get some of those arrestors and fit one by each appliance?

I measured the water pressure and it is 4 bar. I'm sure I read here that it is useful to have a pressure reducing valve set to reduce incoming pressure to 3 bar. Is that right? Would that be a better idea?

Thanks, Stephen.

[Tim+]

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

[Harry Bloomfield]

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.

[Jethro_uk]

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

[Chris Hogg]

+1

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

Another thing you might try is turning down your under-sink stopcock quite a bit to reduce the flow rate when the washing machine or dishwasher are drawing water, although paradoxically, in my previous property, I found that opening it up fully stopped the hammer.

[Chris Hogg]

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.

[DerbyBorn]

Jethro_uk <jethro [e-mail] wrote in news:q4e6ua$1o0$ [e-mail]:

They can be noisy though.

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

[Brian Gaff]

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

[Stephen]

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.

[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.