Knocking pipe

[Naggedalot]

The radiator in my bedroom knocks/bangs at where the pipe fits the valve at the bottom everytime it fires up. It only does this maybe 10 times in rapid succession and then stops....till it cools down and then does it again. Its the side opposite where the thermostat is...any suggestions what it can be?

 

[shorticus]

how long has it been happening?

 

[villa_tom]

Is this an old valve making this noiseor have you had new valves fitted?
It could be the valve on its last legs or the valve could be on the return and not the flow

 

[shorticus]

I was wondering if it might be the pipe creaking against the floor boards as it expands and contracts

 

[Naggedalot]

Its only noticable in winter when the heating kicks in. Its been happening since i bought the house 3 years ago but i thought it was expansion of the pipes on the floorboards...but since the new bathroom (radiator removed to fit tiles) and new boiler were fitted its making a hell of a lot of noise....however, i did loosten the nut that grips the pipe as it comes up from the floor and heard a little rush of air and now its not nearly half as bad as before..but theres still a little tapping coming from there.....how do i extinguish the rest of the air???

Your help is always appreciated no matter how valid it is!!..so thanks guys!

 

[wheeto]

... i did loosten the nut that grips the pipe as it comes up from the floor and heard a little rush of air and now its not nearly half as bad as before..but theres still a little tapping coming from there...

Any chance of a pic?

 

[GrahamM]

Just a simple test to rule out if TRV is on wrong leg.
Put heating on from cold. Feel the two legs. The one with TRV (thermostatic valve) should heat first.

 

[Naggedalot]

Any chance of a pic?

Not got the lead for my camera to hook it up to the comp so cant put a pic up...Its just the standard copper pipe that comes up to a silver right angled valve that connects to the bottom of the radiator....standard setup for a home!

 

[Naggedalot]

Just a simple test to rule out if TRV is on wrong leg.
Put heating on from cold. Feel the two legs. The one with TRV (thermostatic valve) should heat first.

Ahhhh the clicking/knocking valve heats up a lot hotter and quicker than the trv!...and its the same with all the other radiators in the house!!!!!