Another place a frost proof faucet can leak is from the anti siphon portion of the valve if the faucet has one.
Frost free outdoor faucet repair.
Remove the faucet packing nut by turning it counterclockwise with an adjustable wrench.
The packing nut is located directly behind the handle and has six flat sides to facilitate removal with a wrench.
Use lockjaw pliers to support the frost proof faucet body while removing the packing nut.
If your faucet still leaks the stem may be leaking and you should replace the faucet.
Remove the nut then reattach the handle and use it to pull the valve stem straight out.
This component can go bad with use and to repair it you will most likely need a new anti siphon rebuild kit that is brand specific to your faucet.
If your faucet leaks out of the spout when it s turned off the washer is bad.
Most frost free stems are 24 inches long so keep pulling until it s all the way out.