When you turn the handle to shut off the faucet, the stem is screwed down, compressing the washer against the valve seat in the faucet body. The stem is secured by a packing nut, which compresses the packing (twine, a washer, or an O-ring) and prevents water from leaking around the stem. 1  If water leaks around the handle, tighten the packing nut.  If the faucet leaks from the spout, either a washer is defective or a valve seat is badly corroded.