When the spindle is turned down, the washer or disk attached to its lower end is pressed tightly against a smoothly finished ring or ground-seat that surrounds the flow opening to shut off the water flow. If the washer and seat do not make a firm contact at all points, water will leak. This usually happens when the washer becomes worn.
Seats in faucets that are not removable may be reground with reseating tools.
DIY Frequently Asked Questions / Compression Faucet')">
Also known as a washer-type or stem faucet.