Gate Valve

A gate valve uses a flat or wedge-shaped gate that moves up and down to block or allow water passage. When fully open, the gate retracts completely out of the line, creating minimal pressure drop—that's why it's called full-port. When closed, the gate slides down across the seat to stop flow.

In the field, gate valves are the standard rough shutoff for supply lines, mains, and underground service. They're cheap, durable, and hold a seal for years if you don't abuse them. The key weakness is that they're terrible for throttling—opening and closing them slowly creates cavitation and erosion of the gate and seat, so use them for on-off only. Never try to regulate pressure by cracking a gate valve halfway.

Watch for creep and settling in old installations. A gate valve that leaks past the seat usually means the gate or seat is pitted or corroded; they're not easily repaired and should be replaced. On supply lines to houses and buildings, gate valves are mandatory at the meter or service entrance for isolation. They're not a check valve and won't stop backflow.