Towel rail hammering

[STEVEN JOHN]

Hiya, I have a strange issue with - I think my towel rail.

2 years ago I had a new towel rail fitted, and it is located close to the boiler. A few months later I started getting a weird knocking noise just as the boiler switches itself off each time, and a plumber suggested it was something like a "loose jumper" or something of that nature. He sorted it, but a year later it started hammering again as the boiler switches off. I tried turning that towel rail off at its built-in thermostat and the hammering stopped, so I'm certain it's the towel rail. What would cause that and is it easy to fix? I wondered if I can just turn the flow in up a bit to get it warm, but maybe by not having it fully open the pressure won't be as high and the knocking won't happen. Has anyone got any experience of this kind of fault?
Thank you, Steven

 

[Madrab]

That can sometimes be down a directional valve. I.E. the Thermostatic Radiator Valve (TRV) will only work properly with the flow running one way. Check the side of the valve and it may have an arrow on it.

Directional

Bi-directional

 

[STEVEN JOHN]

Thanks for the idea. I can't seem to see any arrows showing me direction. I am attaching images of the towel rail fitting. Does that show anything? Thank you

 

[Madrab]

unfortunately you managed to confuse things by mentioning the built in thermostat. Your towel radiator doesn't have a built in thermostat (TRV), they are 2 manual valves. Your plumber was probably correct and it's down to the manual valves you are using having loose jumpers.

Maybe change to higher quality valves.

 

[STEVEN JOHN]

Ahhh I see. I think I confused myself Rob, as I did ask him to fit a thermostat after the initial installation but held off until I needed other work doing, and it was never done. Loose jumpers on the manual valves makes sense. I turned them down to half way so the rail still heats up, but it seems to have stopped making the noise now so maybe the reduced pressure is helping eliminate the problem. If it returns I'll get the valves replaced. Thank you so much