I have never had a problem with ANY of my installations about leaking air, i simply make sure to cut the tubing squarley and make sure it is all the way on the fittings... I have used plastic BVM fittings and the plastic robart and spring air fittings, I have never used the metal fittings yet..If the fittings are marred from improper cutting or line removal this may be your problem also you may have the wrong diamator line..These guys have covered all the possible ways that you should remove a line if you have it messed up.. I have always used the robart line but latley i have used the colored line from Todd, Still no leaks.. Make sure you are using the right diamator line on your install, i "think" air line is 3mm or just a shade smaller, NOT the 4mm you use for fuel... Russ