Central heating pipe hammer noise

[GRC]

Elderly in-laws had CH serviced recently, and since then, the system has been making intermittent pipe noise - a low drone, lasting for about 15 seconds or so at a time.

It's difficult to pin down an exact source of the noise, but they tell me it seems focused on one radiator, although it can be heard all over the house. It happened a couple of times on my last visit, and FiL told me that he'd made it go away by moving the radiator thermostatic valve to and fro. When it re-occurred, I tried the same, and I could feel a definite judder through the body of the thermostatic valve as I turned it.

Worcester Bosch boiler, around 4 years old, installed and annually serviced by the same firm. There doesn't seem to be any issue with lack of heat, either in radiators or hot water supply. They're all piping hot.

Does this sound similar to anything the CH experts here have encountered before? If so, what was the solution for you?

 

[cross thread]

Some rad valves only have one direction of flow normally indicated by a arrow ,check it first.

 

[GRC]

'twas working fine from installation thru a number of services, and no valves have been replaced. Don't see how direction could/would have changed after a service....?

 

[terryplumb]

Remove the actuator head from the body of the TRV ,just screws off, and see if it makes any difference.