To repair a single-lever faucet, you need groove-joint pliers, an Allen wrench, screwdrivers and needle-nose pliers. You also need the appropriate replacement parts to complete the repair job.
Leaky single-lever faucets are not too difficult to fix if you have the correct tools. Turning off the water is the first step to repairing a dripping faucet. After shutting off the water supply, turn on the taps, and let any remaining water run down the drain. Next, use the Allen wrench to remove the screw on the faucet handle; be careful not to strip the screw. Pull off the handle, and put it aside.
Plug the drain so that small objects like screws do not fall inside. Use the pliers to gently remove the collar around the handle. Find the cam and ball assembly beneath the collar, and remove it. With a screwdriver, carefully remove the springs and washers for the cam and ball assembly.
Fit the new seats and springs with a screwdriver. Next, insert the ball assembly, taking care so that the holes in the assembly line up with the holes in the faucet. Fit the cam over the ball, and put the cap back in place, tightening it so that the ball still feels loose inside the faucet. Finally, attach the handle, and turn the water back on. If the faucet continues to leak, tighten the adjustment ring until it works satisfactorily.