Zip ties on fuel tubing don't work too well. An alternative is to cut a very short piece of fuel tubing (3mm) and use a pair of needle nose pliers to stretch it over the ends of the fuel line and pressure pipes. The outer tubing acts like a very small, strong rubber band and clamps the pipe onto the barbed union.
i dont think I've ever had a fuel line come off.. if they do its prolly time to change them because the rubber is getting weak.. you shouldnt need to zip tie it..