Why Does My Outside Faucet Back up Into Basement?

It sounds like your hose bib froze during the winter and you have a crack in the pipe from the faucet. You probably have a frost-proof sill cock, which actually has a shut off valve inside the house, through a long stem from the handle. The crack is probably tight enough to prevent water from leaking when there is no back-pressure, but the moment you put a hose on and increase the back-pressure it leaks into the house. You will probably need to install a new sill cock. This is not a job for the average do-it-yourselfer. To prevent your outside faucet’s hose bib from freezing, always disconnect water hoses before freezing temperatures arrive and cover the hose bibs with an insulation kit.