I am attempting to plumb the garage so we can move the washing machine out. We have had the mains supply extended so we now have water in the garage in the form of 25mm MDPE pipe capped with an MDPE tap coupler. I have made a T for an outside tap and a washing machine hose connector out of copper pipe and compression fittings and just need to join the two together. For this i have bought the 2.49 Screwfix MDPE to 15mm copper reducer to fit in the MDPE tap coupler. The problem is i dont seem to be able to tighten the MDPE coupler tight enough for the reducer to grip the copper pipe tight enough- when the tap is turned on the pressure slowly but shorely eases the unsecured copper pipe T out. My question is:
1. If tightened enough would the reducer hold it securely or would an MDPE wall plate elbow be better and more acceptable?
2. How would the professionals do this and what would they use to do it?
Many thanks in advance.