have you tried turning off the water and replacing the washer inside?

DFWNurse - hi, if there's not already an access port through the interior wall behind where the hose bibb is located - yes, the plumber would have to cut into the wall. The hose bibb is likely soldered to the water pipe and he can't get to that joint from outside the house - unless he were to cut a fairly large hole around the hose bibb where it sticks through the outer wall. I doubt you or he would want to take that on!

Dircom has a good suggestion to try unless the plumber's already shown you that the hose bibb is cracked or otherwise damaged. Even though the hose bibb may be frost-free, I've seen them get damaged when a garden hose has been left attached to the bibb connection with the water left on in the winter.

I hope this helps you some - good luck! Jim D/West Point, VA

I join Jim in his comment about hydrant barrels that have split because the hose was left on and the water was not allowed to drain out. They freeze, expand and split the barrel. The quick disconnects will also hold the water in on vacuum and result in freezing.

Some hydrants do get worn with age resulting in the stem threads becoming smaller and not holding into the barrels threads.

I replace 5 to 10 freeze-resistant wall hydrants a year and do need access to change them.