Don't listen to "them!"
It depends on which On/off valve you get. A lot of the on/off valves that have screw knobs leak freaquently. I had htis problem. instead of getting a new vavle I got a smart parts on/off valve. They're really easy to turn and you only have to turn the little knob 1 revolution to open and to close it. I have yet to have problems with it. If you want a co2 on/off valve then get a smart parts on/off valve. Its the one with the little blue knob on it.
-WGP '02 Autococker : Powerlyte Scepter Kit, KAPP Reflex Hinge, Besales Hollowpoint 3-Way, Palmer's MicroRock adj., KAPP F.A.T. Ram, PMI Pure Energy 4500 68ci,
-'99 F4 Illustrator w/upgrades