Clunking noise - Desperate - Please advise.

[QuickQuestion]

I have an old Potterton Kingfisher floor standing boiler. My hot water is gravity fed and my heating is pumped.

The problem I have is there is a loud "clunk clunk" noise from somewhere (sounds like from a pipe). This noise occurs when the HW only is on, and when it gets to a certain temperature. When the boiler fires down, so the "clunks" get slower until it stops. Now, this is the strange bit, if I turn on the CH, the noise does not occur. Even more strange is the fact that when the HW only is on and I isolate the pump, the noise stops. As soon as I turn the wheel to re-instate the pump (not pumping of course), the noise starts again. Now, when my kitchen was modernised, the pipes from the boiler run behind a stud wall. I did notice before that there was a check valve on the CH flow pipe half way up the wall. My only thought is that this has failed and the heating of the water in the flow pipe is enough to agravate the check valve (loose part inside maybe) and it makes it rattle, but I haven't convinced myself this is the problem. If the valve was faulty, surely upstairs rads would become a bit warm.

So you see, I am totally puzzled! Anyone got any suggestions as the noise is doing my head in!

Many thanks.

 

[kevplumb]

boilers kettling get some cleanser in the system

 

[mickyg]

An old cast iron floor stander on gravity hw....clunking.
I would be more surprised if it wasn't!

 

[QuickQuestion]

boilers kettling get some cleanser in the system

Thanks for the reply. It's not kettling. It's not coming from the boiler. Had kettling before and treated the system with boiler silencer. It really sounds like a noise from a pipe. Besides why would kettling stop when the pump is isolated?

 

[mickyg]

aah..just bothered to read the whole post
yep, it sounds like the non-return valve maybe rattling. Had it couple times before.

 

[QuickQuestion]

aah..just bothered to read the whole post
yep, it sounds like the non-return valve maybe rattling. Had it couple times before.

Ah, so I am assuming isolating the pump stops any movement of water up the flow pipe via gravity? Therefore, if I was to put in a 2 port motorised valve on the flow pipe, to open when the pump starts, that should cure it? I can't get to the check valve as it is behind a wall! Thanks for the replies so far.

 

[kevplumb]

err methinks not

you could try a "c" plan

 

[QuickQuestion]

err methinks not

you could try a "c" plan

Why not?

 

[kevplumb]

you don't put a valve on the flow

exepting the one you have

 

[QuickQuestion]

you don't put a valve on the flow

exepting the one you have

I have no valves at all on my system. C plan is where the valve is on the gravity hw circuit, right? Then that would make no difference to my annoying clunking noise.

 

[kevplumb]

if mickeyg is right you have an anti gravity valve on the flow

 

[QuickQuestion]

if mickeyg is right you have an anti gravity valve on the flow

Yes, I do, behind a wall. But no motorized valves.

 

[kevplumb]

alright pedantic

you don't put a valve on the flow exept

on a "c" plan it goes on the return

 

[doitall]

What non return valve did they install, is it the sprung loaded or clacker type.

The later usually is more a metal to metal tinkle/rattle.

 

[mickyg]

I can't get to the check valve as it is behind a wall!

well live with the noise then!