One of the advantages of yard hydrants is that they are adjustable. For instance, if the handle is almost all the way down before the resistance felt when the plunger hits the valve seat, the hydrant may need adjusting. This problem occurs when the linkage is starting to show wear and does not force the rubber assembly all the way into the valve seat. You can often fix the problem by adjusting the nuts or by a combination of replacing the gaskets and adjusting the nuts.
Loosen the set screw located in the side of the pivot while the hydrant is in the closed position.
Raise the handle. The linkage should lift with the handle while the stem stays in place. When the handle is in the correct position, retighten the set screw.
Repeat the adjustment until it's perfect. If increasing the tension does not fix the problem, try loosening the tension.
Lift the handle part of the way up. Loosen the set screw.
Lower the handle a little bit. This will move the linkage without moving the stem.
Tighten the set screw with the handle in the new position. The handle should snap closed at the end of the closing stroke.
Remove the lower link bolt, which connects the lower link to the clevis assembly.
Loosen the set screw in the lower link. Turn the lower link counterclockwise to increase the tension. To decrease tension, turn the link clockwise. Test the pump. The handle should snap closed. Adjust until it closes correctly.
Tighten the set screw and reinstall the lower link bolt.