I suspect there is no problem with the faucett. The problem is a slight operator error because no one bothered to explain to the homeowner how a frost proof faucet works.
Notice from the illustration, the wall flange is mounted flush with the exterior wall of the structure and there is a long tube which passes through the wall with the actual valve seat and bibb washer on the interior end of the assembly which is within the heated portion of the structure (this is what is technically referred to as a Hydrant).
When water is turned off the stem presses the bibb washer against the seat and the water is cut off on the interior end of the tube. The residual water remaining in the tube from the bibb washer to the mouth of the faucett is intended to then drain out so there is no water in the exterior part of the faucett that could freeze.
Quite often ppl who do not understand the function assume that residual water that still comes out is leaking past the valve so they attempt to further tighten the valve, which only leads to excessive mechanical pressure on the bibb washer causing the washer to be distorted and premature washer failure.
The problem can appear even worse if there is a hose attached that has a closed nozzle on the output end. In this situation as the faucett is turned off the residual water is trapped in the faucett & hose. The actual working pressure drops but both the faucett and hose still remain full of water so if the hose happens to be heated by sunlight the water in the hose will expand and cause a backpressure to the silcock, which is then discharged through the anti-siphon backflow preventer and giving the illusion that the valve is leaking.
Properly a hose should be disconnected from a frost proof silcock as soon as you turn the water off, but in the real world we all know that is seldom if ever done.
There is a quick, simple and cheap solution. Install a plastic "Swiss Tee" on the hose thread of the faucett, then attach the hose to one side of the swiss tee. When you need the hose you can open the swiss tee to the hose and when you want to fill a pail or something directly from the faucett you can switch the hose side off and open the other side of the swiss tee to use the faucett directly.
When turning the water off, open the side of the swiss tee opposite the hose connection and leave it open. The frost proof silcock can then drain in its proper manner.
Q
