I know how to fix the leak. What I don‘t know is if there still should be pressure when the valve is shut off. Is that a bigger problem that I should have a professional check out or is the pressure, when the faucet is off, just the result of the hole in the pipe?
The water pipe should always be under pressure unless you shut off the water to the whole house. The faucet simply lets water out of the pipe when you turn the faucet on. Shut the faucet off, there is still water in the pipe under pressure. Repairng copper pipe is really simple if you know how to sweat a fitting (use solder to seal the repair). First shut off the water to the entire house. Then cut the copper line with a tube cutter on each side of the leak. Do Not use a saw, that will leave a jagged edge, jagged edges create a gap between the fitting and the copper pipe. Measure and cut a piece of copper pipe to fit in the open gap you made when you removed the piece with the leak. Use a copper pipe brush and remove the glaze / corrosion on the outside ends of all pipe. Remove the glaze inside the pipe couplings. Drain the water from the copper pipe, then stuff the center of a piece of bread in the pipe to prevent any more drips from getting the area wet. Don't worry, the bread will dissolve when you turn the water on and flush out the faucet. Coat the brushed ends and the inside of the couplings with Flux. Install the couplings and repair piece on the copper pipe. Using a torch, heat each side of both couplings enough that the solder will melt and be drawn into the joint when the solder touches the joint. Caution if you get the pipe too hot, you will not get a tight seal. Let cool. Turn the water on and flush the bread out the faucet. If you were good a sweating the parts together, it will not leak. If you do not have a tube cutter, flux, solder, torch and the parts to repair the leak, a plumber will cost about the same as the parts and tools, and will do the job for you in less than 5 minutes.
Is there a ball valve behind the hydrant? If not, there should be. The hydrant will still have pressure on it when the hydrant is shut off. The purpose of the ball valve is to isolate the hydrant from the rest of the system so you don't have to shut off main service to work on the hydrant. If there is no ball valve, you will have to shut the main off to work on the hydrant. As long as you are there, you may as well put a ball valve in and bring it into compliance.
Depends on what kind of spigot is on the pipe. A freeze-proof spigot will have the valve farther back, where it's less likely to freeze in winter. Even so I don't think you'd be able to replace the pipe without turning off the water first; even a freeze-proof spigot will require some dismantling to replace the delivery pipe downstream of the valve.
The water pipe should always be under pressure unless you shut off the water to the whole house. The faucet simply lets water out of the pipe when you turn the faucet on. Shut the faucet off, there is still water in the pipe under pressure. Repairng copper pipe is really simple if you know how to sweat a fitting (use solder to seal the repair). First shut off the water to the entire house. Then cut the copper line with a tube cutter on each side of the leak. Do Not use a saw, that will leave a jagged edge, jagged edges create a gap between the fitting and the copper pipe. Measure and cut a piece of copper pipe to fit in the open gap you made when you removed the piece with the leak. Use a copper pipe brush and remove the glaze / corrosion on the outside ends of all pipe. Remove the glaze inside the pipe couplings. Drain the water from the copper pipe, then stuff the center of a piece of bread in the pipe to prevent any more drips from getting the area wet. Don't worry, the bread will dissolve when you turn the water on and flush out the faucet. Coat the brushed ends and the inside of the couplings with Flux. Install the couplings and repair piece on the copper pipe. Using a torch, heat each side of both couplings enough that the solder will melt and be drawn into the joint when the solder touches the joint. Caution if you get the pipe too hot, you will not get a tight seal. Let cool. Turn the water on and flush the bread out the faucet. If you were good a sweating the parts together, it will not leak. If you do not have a tube cutter, flux, solder, torch and the parts to repair the leak, a plumber will cost about the same as the parts and tools, and will do the job for you in less than 5 minutes.
Is there a ball valve behind the hydrant? If not, there should be. The hydrant will still have pressure on it when the hydrant is shut off. The purpose of the ball valve is to isolate the hydrant from the rest of the system so you don't have to shut off main service to work on the hydrant. If there is no ball valve, you will have to shut the main off to work on the hydrant. As long as you are there, you may as well put a ball valve in and bring it into compliance.
Depends on what kind of spigot is on the pipe. A freeze-proof spigot will have the valve farther back, where it's less likely to freeze in winter. Even so I don't think you'd be able to replace the pipe without turning off the water first; even a freeze-proof spigot will require some dismantling to replace the delivery pipe downstream of the valve.
