The O-Rings in a simple Ball Valve cannot be accessed so there is no way to replace them. When the valve starts to leak, the whole Valve has to be replaced. If you want to access the O-Rings, you must buy a Ball Valve that has one or two unions. The Ball Valve shown here has a single union that will allow you to pull out the Valve Stem and replace damaged O-Rings. You will still have to cut out the Valve on the side that has no union.