Banging despite arrestor being fitted

[Beercan]

Hi all,

Whenever a cold tap or the washing machine is used in our house there is a single bang each time as it is turned off. This can be heard around the house but is loudest at the combi boiler in the upstairs airing cupboard. There is a shock arrestor fitted near the boiler which I have recharged to 5 bar as per the label, but the bang persists.

I have reduced the mains pressure via the stopcock which fixes the bang but now the flow is insufficient.

How can I fix this please?
Thanks for reading!

 

[Aquarius]

I have reduced the mains pressure via the stopcock

No you haven’t, you’ve answered your own issue, as you have reduced the flow, not presssure. To reduce the pressure would require a pressure reducing valve.

Are your pipes clipped correctly? Is it a new build property? Is it plastic piping?

 

[John.g]

I presume you are talking about the pre charge (air) pressure. If this equals or is > the mains pressure then it won't do much good, if you don't know the mains pressure suggest reducing this to say 2 to 2.5 bar and see how you get on.

 

[Beercan]

Thanks for your replies.
I don't know the mains pressure as I don't have a device to test this.
Pipes are clipped everywhere I can get to them.
The house is c. 1960. It's got a mix of copper and plastic on both the hot and cold.
Thanks!

 

[Scott_D]

What boiler is it?
Does it try to fire for hot water each time?
Any obvious deadlegs in an airing cupboard for example?

 

[townfanjon]

The shock arrester is to protect the boiler not the house plumbing .
As above from all the guys ^^^^^^ is your way forward, can be a nightmare to find , its usually a badly clipped pipe in my experience.