But you don?t need to call a plumber and spend money on a service call with a few easy steps you can become your own ?master plumber? The first thing you need to do is turn off the water supply to the sink, most of the time the valve is located right underneath, if not you need to follow the plumbing line to the nearest shut off valve. If the valve resists being turned, put a drop or two of oil right where the stem disappears into the large nut. Then use a wrench to loosen the nut one complete turn, and tighten it back up by hand. Wait for a couple of minutes and then you should be able to turn the valve off. The second thing to do is remove the stem from the top of the fixture, then there will be nut that needs to be turned counterclockwise to be taken off. Grasp the handle and turn it counterclockwise, as if you were turning on the water. The whole thing will lift out in your hand. If you have a ball-type fixture, there will be a setscrew on the lower surface of the handle itself, remove the screw. There will be a plastic ring or cap just unscrew and remove then pull out the ball assembly. Your almost finished, just need to replace the washer, which should still be attached the ball assembly you just pulled out, there?s a screw holding it on so remove that, replace it with the new washer, tighten the screw back on, be sure not to go to tight where the washer starts to become damaged. Reinsert the stem assembly, and twist it firmly clockwise (don't over tighten it). Tighten the large nut back into place. Turn the water valve back on and that?s it! If it still leaks it may mean you have to replace the valve seat or replace the entire fixture. You will need to purchase a repair kit that you can find at your local plumbing supply or hardware store. Use the following steps to replace the ball type fixture: Using the end of the screwdriver, lift out the rubber seats and springs. Replace them with the new ones in the kit. Tug the spout off the base by turning it from side to side and lifting up. Then use the screwdriver to leverage the old O-rings off the base. If they need to be cut off, make sure that you clean off any remaining pieces. Roll the new O-rings over the base to replace them. Re-seat the faucet by turning it from side to side while pushing down. Place the ball assembly back in there, and screw the rounded, knurled cap back on. Before retightening the adjusting ring with the special tool, turn the water back on. Then tighten the ring until no water leaks, but don't over tighten it. Replace the handle, and tighten the setscrew. You should be all set! It?s a good idea before starting this job to go to your local plumbing supply with the make of your faucet just to make sure that all the necessary parts are available