Possible water hammer?????

[zooankski]

I have been suffering from a strange issue the last few months.
I appear to be getting water hammer in the cold feed to my megaflop cylinder.
the noise starts when any tap or toilet flush , any where in the house is operated and starts off a quite a fast knock which progressively slows and stops over 30 seconds to a minute.
I rang heatre sadia to ask because the feed is to the tank and they suggested an arrestor fitted before the 3 bar inlet valve. I had this fitted but it has made no difference.
The only thing that will stop the knock instantly is shutting the balanced supply feed down off.
Does any one have any suggestions for a fix?
I thought perhaps a one way valve just before the down shut off as i cannot see this effecting the cylinder feed?? also perhaps a one way valve in the 15mm feed which was tapped off to teed the shower in the loft just to illuminate any possibility that is the cause?

Untitled

• zooankski
• 14 Jan 2015
• 1

Untitled

• zooankski
• 14 Jan 2015
• 1

Untitled

• zooankski
• 14 Jan 2015
• 1

 

[Groovejet]

Usually things like this are caused by a loose jumper valve/washer inside a gate valve ,stop cock wc ball valve or service valve ....the latter the least!

A case of methodically checking individual fittings. Get a screwdriver, i normally use a long 600mm one, and hold it to a gate valve or whateva and listen with your ear on the shaft end.
It acts like a microphone and you can hear noices your wouldnt normally be able to hear

 

[zooankski]

I will give it a go.

 

[Alex10]

My advise is install a shock arrester to cold main.

 

[zooankski]

shock arrestor has made no odds. I noticed last night that i can here the 8 bar pressure relief valve "clicks" before you get the thud in the pipe, click, thud, click, thud .....
Matbe relacing that although i don't understand why shutting cold service down off stops it.

 

[gigz]

Get a qualified engineer to check the combi valve.

 

[Madrab]

Just to be clear, is it the Pressure relief/combi valve you are talking about? -

View media item 88513,
if so do you see water, drips in the tundish when it happens, should be position downstream on the relief valve's pipework

or the pressure reducing valve/strainer?

View media item 88514
Either or, as Gigz mentions, get an engineer qualified in un-vented supplies, to give it the once over, should really be checked once a year to check/test all the safety devices.

 

[Alex10]

Might be prv chattering then. As above replace combination vlv