best way is a brass hoselock female connector, they are expensive each, but dont leak, also if its not the o ring part its leaking from but where the hose connects, unscrew the bit that clamps down on the pipe, then cut off all the little bits that clamp onto the hose, or take out the plastic bit if its a brass one, then leave the screw on part off, and put a jubilee clip over that part, then it will never leak. I have never found plastic hoselocks to be any good they allways leak.
brass is best with the ball bearings that hold it onto the male fitting.