Cold water feed inlet to boiler has burst?

I have a Ravenheat and the cold water inlet pipe to the boiler is plastic. The pipe came away from the filling loop at about 6.30 when the heating came on causing a flood. I repaired it. The next morning about the same time the same pipe near to the inlet underneath the boiler burst. I replaced it. About the same time the following morning the pipe burst in the same place again. What could be causing this? Does the central heating coming on have anything to do with it? I thought maybe not as the cold water feed is to supply hot water. Although it does seem to happen around the time the heating comes on. Please help!