Water hammer - not TRV

[DJM]

Recently started to get a water hammer like sound - very much like a stuttering TRV. Gone round every radiator and none seem to be the issue.
Finally chased it down to the airing cupboard and pipes from the hot water cylinder. Motorised valve situatred there and if manually turned then noise stops.

Any suggestions as to cause and repair?

 

[D_Hailsham]

Just one valve - like this?

View media item 5946
Is valve connected right way round? Port A to rads, Port B to cylinder (port names on side of valve brass part)

Which make valve?


It could be the inside of the valve has broken.

 

[DJM]

Sorry, better clarify.

System has worked fine for the past 5 years and has only recently started the hammering, so connections must be assumed to be correct.

I am at work, so can't check for certain, but am pretty sure that we have seperate motorised valves for heating and hot water. Heating valve down by boiler and HW in airing cupboard by HW cylinder.

Water hammer is not constant and does not always happen. Mostly at night later in the evening, when I suspect the cylinder is at thermostat temp.

When I get home I'll have a look for make etc.

 

[DJM]

Motorised valve is a honeywell

 

[Biguns]

Whats your boiler/system? I recently had this problem on my system- old apollo boiler. What I found was, after the heating had been on for a while, the room stat would demand heat the boiler would fire but occaisionally the pump would'nt which caused hammering with the boiling water going straight to the EF tank. kevplumb advised renewing the pump overrun stat, which I did and it worked

 

[DJM]

Boiler system is an Ideal balanced flu Fl100 IIRC gravity fed. All radiators have TRVs so no room stat, but obviously frost stat near boiler. Bathroom radiator controlled by hot water timer. Pump runs when on so don't think it's the problem you suggest snugib

D_Hailsham, yes it is a std Honeywell valve similar to your picture.

 

[D_Hailsham]

D_Hailsham, yes it is a std Honeywell valve similar to your picture.

It can't be similar.

You either have (a) one 3-port valve, as in the left picture, or (b) two 2-port valves, as in the right pic. Which is it?

View media item 5946 View media item 11762

 

[DJM]

Sorry for not being clear, but I did say we had seperate valves and not a 3-way, so like your RH picture.A couple of snaps below

 

[D_Hailsham]

Sorry for not being clear, but I did say we had separate valves and not a 3-way, so like your RH picture.

I missed that bit about two valves - must read more carefully.

Can you check that the valve shown in the pic is the correct way up? There is an arrow on the brass body. This should point up, in the direction of flow.

 

[DJM]

I'll have a look tonight when I get home, but as it has worked perfectly for the past 5 or more years since it was put in, I suspect it is the right way round.

 

[jackthom]

I've got one of those valves next to me and I'm pretty sure from the photo the direction will be upwards. The power cable and lever are on the input side.