double check valve - noise & screw

[gregd72002]

Hello,

I've got a new boiler installed recently. The system was converted from vented to sealed. It has also 2 double check valves - first on the mains just before pressure reducing valve for my property and the other one on mains inlet to the boiler.

This overall works great, though the second double check valve (one installed on mains inlet to the boiler) makes horrible noise when DHW is on!

The valve looks like this one:

I think I will simply get a new one and install it in place of this one, however before...
Can someone tell me what is the screw on top of the valve for?

Thanks[/b]

 

[Dan Robinson]

Might be some c7ap in it.

 

[gregd72002]

Might be some c7ap in it.

Thanks Dan. What about the screw on top of the valve - what is it for? Can I turn it left-right ... without shutting off mains?

 

[Dan Robinson]

Its just there to verify the valve is "checking".

It is a cap.

It won't affect any noises.

 

[gavinda]

Could he not get rid of the non return entirely or am I missing sOmething.

 

[gregd72002]

Could he not get rid of the non return entirely or am I missing sOmething.

gavinda, actually I did not have the valve at the first place at all and
I had a problem..

whenever I switched on cold water the boiler was firing up for a second or so. This was due to an interim pressure drop on the mains inlet to the boiler and the boiler was heating up the wrong side of DHW I could confirm it by simply touching the inlet pipe and indeed, it was getting warm.

Fitting in the valve solved the problem.

I guess your next suggestion will be that there must have been a dead leg somewhere. This is very true, there possibly is one but is buried under a concrete floor so I do not really fancy looking for it....

 

[gavinda]

fair play

 

[doitall]

Actually

Is the valve the right way round, otherwise as Dan said it may have a bit of crap init.

The thing in the middle, for education purposes only, is to drain the valve for frost protection/winterizing.

 

[gregd72002]

[...]
Is the valve the right way round
[...]

I would not have hot water at all if the valve was the wrong way in? (the valve would block the inlet).. I do have hot water - so I presume is the right way in

[...]
The thing in the middle, for education purposes only, is to drain the valve for frost protection/winterizing.
[...]

Can I open it to clear the insides? Ie. remove the crap

 

[gavinda]

if to remove it, you MIGHT be able to push it open and flush it through. do it into a clean sink with the plug is. then you will see if any shiz came out. if not then i guess its time for a new one. possibly put a line filter in front of it so save le hassle in le future.

 

[doitall]

You could try, turning the mains off and removing the cap, then give the mains a quick blast into a bucket.

 

[Charnwood]

The thing in the middle, for education purposes only, is to drain the valve for frost protection/winterizing.

Is it really? And there's me thinking it was a test point.

Strangely, most manufacturers call it a test point. Perhaps they ought to read this forum and learn a thing or two.

 

[doitall]

The thing in the middle, for education purposes only, is to drain the valve for frost protection/winterizing.

Is it really? And there's me thinking it was a test point.

Strangely, most manufacturers call it a test point. Perhaps they ought to read this forum and learn a thing or two.

Always been for draining the water out between the checks, if you need to winterize the pipework etc.

 

[Dan Robinson]

Not had it with double check valves that I can remember, but have had this with single check valves, which turned out just to be an iffy valve.

 

[silverback]

The thing in the middle, for education purposes only, is to drain the valve for frost protection/winterizing.

Is it really? And there's me thinking it was a test point.

Strangely, most manufacturers call it a test point. Perhaps they ought to read this forum and learn a thing or two.

Always been for draining the water out between the checks, if you need to winterize the pipework etc.

No it is not, it is a test point for monitoring correct functioning of the downstream check valve

http://www.rwc.co.uk/Public/backflow/flowdcv.pdf