banging rad

[snipper]

help......... i have a problem ......sime frendly format combi boiler working fine but i have an upstairs rad (first inline from boiler i think) that seems to bang as the boiler fires up as the rads warm and then bangs as the boiler cuts out and pumps the water round.you can feel the slight knocking on the pipes to the rad as they come out the floor.this has me baffled as nothing has been touched all the years its been in so i dont think any of the pipes are tight in the joists and ...radiators bled....boiler pressue correct.....water temp set at 65/70.............so any help would be greatful

cheers snipper

 

[kevplumb]

have you got a trv on it ?

 

[snipper]

trv??

 

[kevplumb]

thermostatic radiator valve
has it got numbers on it ?

 

[snipper]

no numbers lol....just a main thermostat to the boiler...........could it be the water pump in the combi not circulating that water as fast as it was so the first bit of pipe and rad are to hot ? just a thought

 

[kevplumb]

could be the diverter valve not closing properly and slowing the flow
recent problem

 

[snipper]

wouldnt a faulty diverter valve affect the hot water supply ? i dont know much about boilers

 

[kevplumb]

not if sludge crud in the system is restricting the movement of said valve
i assume you hit the wrong smieley

 

[snipper]

do you think if i drain the system and refill it will help at all?

 

[kevplumb]

no