PEX expands and contracts more than copper, so don’t stretch it tight. Let it droop a little between fasteners. On long runs, it’s a good idea to install a loop as shown to allow for contraction. Another advantage of the loop is that if you mess up and need a little extra tubing, you can steal it from the loop. Also, since PEX moves as it expands and contracts, make sure to drill oversize holes through studs or joists so it can slide easily, and don’t use metal straps to attach it. Use plast...