OS&Y Valves

Critical Access to the Water Source When You Need It Most

The OS&Y valve may have an intricate name, but its mechanical function is very basic. First, it is a gate valve, meaning that the flow of water is controlled by the movement of a barrier, also known as a gate. The gate is perpendicular to the water’s path, and when it is pressed down against the valve seats, a seal is formed, and water cannot flow. Pulling the gate away from the valve seat lets the water through.

This is part of our fire protection products because an OS&Y valve is often used to control the water flow to a fire sprinkler or standpipe system. If the main control valve is closed, the system is effectively off. Every sprinkler system needs at least one main control valve—usually on the riser between the water main connection and the system’s network of pipes.

What Is An OS&Y Valve? 

A common question, not often asked but usually thought: “What do the letters OS&Y stand for?”  The letters stand for “outside screw and yoke” (or, occasionally, “outside stem and yoke”). The gate is attached to a threaded screw or stem that is fitted into a handwheel, and the handwheel is held in place by a yoke. Turning the handwheel moves the stem and gate up and down.

Why An OS&Y Valve Is Helpful

OS&Y valves make excellent fire protection valves because they have these two critical features: 

1. they are indicating 
2. they take at least five seconds to close
3. they are UL-listed and FM approved

As their name implies, indicator valves indicate whether a valve is open or closed. This feature is vital because control valves that are closed by mistake are the number one cause of fire sprinkler failure.

Secondly, a sprinkler valve must close slowly to avoid water hammer. A water hammer is a dangerous surge in pressure that can happen when water flow is stopped quickly.

The OS&Y valve clearly indicates its state: it’s open when the stem is up. When the stem is down, the valve is closed. The handwheel must be turned multiple times to close the valve, taking at least 5 seconds. This incremental closing protects against pressure surges.

We Have The OS&Y Valves You Need

The OS&Y valves at United Brass Works are made of brass, bronze, steel, and iron and are 100% pressure-tested. Whether you need a large order for a construction project or just one replacement component, we’re your resource for fire protection valves.