On our 94 Fleetwood Wilderness trailer, I have grey tubing that goes to the water heater. These lines are both cut and I believe the tubing is called PEX, is that correct? I know that PVC fittings do not glue on to them because I tried and it didn't work. The fittings are all crimped on the original pipes. Do I have to get a crimping tool and special fittings to connect these lines together or is there some other way. I was going to change all lines to PVC but I can't get to the lines in the bathroom without tearing a lot of things out. I do need some advice here.