I have recently installed some 15mm JG speedfit pipe for radiator flow/return. On cooling down (i.e. as central heating is turned off) - get a ticking/clicking almost dripping noise near one of the elbow connections in the corner of the room - certain it is not the elbow connection itself rather where the pipe is cliped as it is clipped all along the wall. I have read this might be common as pipe contracts and is tightly clipped - question is whether it is a long term issue or matters?