The back-flow preventer on my outside tap was leaking where the preventer screws onto the tap. When I tried to loosen the locking screw to tighten or remove the preventer, the screw snapped off. Yep. The back flow preventer doesn't bother me per se, but I would like to use timer value on the tap for irrigation. Right now, if I add a timer valve and open the tap, I get a steady drip from the tap. Is there any way of sealing the tap-preventer junction?