ChatterBank2 mins ago
Central heating
Answers
No best answer has yet been selected by Loosehead. Once a best answer has been selected, it will be shown here.
For more on marking an answer as the "Best Answer", please visit our FAQ.Loosehead, check to see if you have little plastic inserts in the support brackets where the radiator sits in them. A big radiator will move slightly in them when heating/cooling and they should help it move quietly. Replacing some of the copper pipe to the rad with plastic will negate any expansion in the pipe.
Jaytee, I recently answered a similar question. This is water hammer, a hydraulic shockwave usually caused by loose copper pipes moving when a tap or valve is turned off quickly. You can fit a water shock absorber or accummulator in the cold supply to stop it or replace some of the copper pipe with plastic or secure any loose pipes.