Repeated burst mains water, any plumbers?

Hi everyone,

Apologies for a multiple post but I thought some plumbers might be reading this forum....

A few weeks ago a cold water mains PVC pipe split just above its joint to a copper elbow leading to the cold water intake on the HWS. Luckily it was reasonably accessible. Thinking I didn't have the tools (ie crimper) to fix it I got a plumber to come out. He replaced the split section using joiners fairly similar to those you'd use on your garden hose, which is fine but of course I could have done that myself. Anyhoo about a week later the pipe burst again, the old hose about 2 inches above the fix. Thus nothing to do with the plumbers work but how unlucky eh? SO this time I fixed it myself using a longer piece of new pipe and the clamps/fittings used in the previous fix. Job done. Until today when the old pipe, about an inch above the fix burst AGAIN. Each time it's been when the washing machine's on which I initially thought was the culprit but the last 2 times I've had the cold water dialed right down to relieve any of those "pressure surges" solenoid's can create. In any case the mains should be able to handle it and for it to burst 3 times in the same spot is really weird. The pipe was fixed to the framing pretty well and not rubbing against anything. Why has it done this?!?! Now i've replaced about a 4m section with the join in the roof. The only idea I had was that that part of the pipe that failed might have had some manufacturing flaw that resulted in the 3 ruptures. going 4m's back I'm hoping that this will be the end of it but i'm scared of it happening again in a) the roof of b) elsewhere in the plumbing.

The plumbings 8 years old.

Any advice guys?

Sean

YOU CAN INSTAL HAMMER ARRESTORS MADE BY RMC BEHIND THE HOT AND COLD TAPS FOR YOUR WASHING MACHINE THIS SHOULD REDUCE THE SHOCK