Things You Will Need
Wrench (open end or adjustable), Phillips or flat blade screwdriver, Teflon pipe tape, Replacement washer, Vaseline or silicone grease
The first step is to turn off the water supply upstream of the faucet. Usually the best place to turn off the water is at the valve located on the house side of the water meter. Sometimes there is a shut-off valve located in the basement for the individual outside faucet. Turn the faucet on to make sure the water is off.
Open the faucet completely. While holding the faucet in place with a wrench or large pair of adjustable pliers, remove the valve assembly by using an adjustable or open end wrench on the section below the compression nut. (The compression nut is the nut just below the handle.) Many houses in colder climates have freeze proof outdoor faucets that have valve stems that are 12 to 15 inches in length to keep the water in the warmer areas of the house to prevent freeze damage. In warmer regions the valve stems are only a few inches long. The seating washer (compression washer) is located at the end of the valve stem. Remove the retaining screw holding the washer and use a small flat blade screwdriver to pry the old washer out. Replace the washer with a new one of the same size and shape. Replace the retaining screw tightening it with a screwdriver.
Make sure that the handle of the valve is opened completely. Wrap Teflon pipe tape on the outer threads of the valve assembly. Reassemble the faucet by screwing the valve assembly into the fixture and tighten it with the adjustable wrench. Be sure to hold the faucet in place where it connects the building while tightening the valve assembly.
Turn the water supply on. If the faucet is leaking around the packing nut try to gently tighten the nut. If the leaking does not stop, the packing washer or graphite string will have to be replaced. Turn the water supply off and remove the handle. Loosen and remove the packing nut. Replace the packing washer with another packing washer or graphite string and retighten the packing nut. Replace the handle and turn the water supply back on to check for leaks.
Replacing a washer that is wearing out is easy and straight forward. The whole job takes only about 10 minutes. So practice your DIY skills and save yourself money by replacing the washer without having to pay for a professional plumber.
Tips & Warnings
There are inner threads on the valve stem that can be lubricated with Vaseline or silicone grease to help make the faucet turn easier.