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Gate Valves

Gate valves are used when a straight-line flow of water with minimum flow restriction are needed.

They get their name from the gate-like disk that slides across the path of the flow. Gates are formed by machining both sides of the metal disk and both faces of the vertical valve seat.
Gate valves are classified as either rising-stem or non-rising-stem valves.

In the non-rising stem design, the stem is stationary and the gate rises on a spindle. As the handwheel on the stem is rotated, the gate travels up or down the stem on the threads while the stem remains vertically stationary. This type of valve will almost always have a pointer indicator threaded onto the upper end of the stem to indicate the position of the gate.
In a rising stem design the gate is affixed to the stem and the stem itself rises along with the gate. Valves with rising stems are used when it is important to know at a glance whether the valve is open or closed and when the stem and gate could become damaged by fluid contaminants if exposed to the fluid. In this type of valve, the stem rises out of the valve when the valve is opened.

The non-rising stem type is more common in residential water systems.
In either case, the gate is usually wedge-shaped. When the valve is wide open the gate is fully drawn up into the valve bonnet.

This leaves an opening for flow through the valve the same size as the pipe in which the valve is installed.

The valve provides an unobstructed waterway when fully open. It is best suited for main water supply lines and for pump lines.

Flow-control is impractical with these valves because of their design, and the flow of fluid pressing against a partially open gate can cause extensive damage to the valve. Except as specifically authorized, gate valves should not be used partially closed.
Gate valves are available in either IPS threaded (FIP) or CTS sweat styles in all common sizes.

They’re typically sold with a handwheel handle. These valves usually require several turns of the handle to fully close or open.

They have long been the choice for main shutoff valves in residential plumbing systems, but are now often being supplanted by ball valves.

Their main weakness is the gate itself, which sometimes detaches from the stem and fails after long-term use. And in an emergency, they require several turns of the handle to close whereas a ball valve closes in a quarter turn.

 

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