FIFFCO OS & Y Gate Valve commonly used to control water flow to fire sprinkler systems. OS&Y means “outside stem and yoke” or “outside screw and yoke”. OS&Y gate valves operate by opening and closing via a gate, which lowers into or rises out of the valve. Raising the gate allows water to flow through the valve while lowering the gate cuts off the water flowing through the valve. When fully open, the typical gate valve has no obstruction in the flow path, resulting in very low friction loss.
When water flow control matters most, you need a valve you can trust without question. The FIFFCO Standard OS & Y Gate Valve (Model FS101) is engineered specifically for fire sprinkler systems where precision, durability, and compliance are non-negotiable.
OS&Y stands for Outside Screw and Yoke — a design where the valve’s open or closed position is always visible from the stem, making it the industry standard for fire protection applications. When the stem is extended outward, the valve is open. When it’s flush, it’s closed. Simple, reliable, and inspection-friendly.
FIFFCO has built this valve to perform in demanding environments, backed by a ductile iron body, full waterway design, and fusion bonded epoxy coating for long-term corrosion resistance.
The FS101 is not just another gate valve. Every specification is chosen for fire protection performance:
This combination of materials and engineering makes the FS101 a dependable choice for fire protection engineers and contractors across the UK and Middle East.
The FIFFCO FS101 fits into a wide range of applications beyond standard sprinkler systems. Fire protection engineers specify this valve across:
The flanged design makes installation straightforward, and the visible stem means maintenance teams can confirm valve status at a glance — an important advantage during fire drills and compliance inspections.
For projects requiring UL Listed gate valves, FIFFCO also offers the FC115 UL Listed OS&Y Gate Valve, designed to meet AWWA C515 valve standards for North American-influenced specifications.
Q1: What does OS&Y mean in a gate valve?
OS&Y stands for Outside Screw and Yoke. It refers to a gate valve design where the threaded stem is located outside the valve body. As the valve opens, the stem rises visibly — allowing inspectors and engineers to confirm the valve position without touching it. This makes OS&Y gate valves a preferred choice in fire sprinkler systems.
Q2: What is the working pressure of the FIFFCO FS101?
The standard working pressure is 300 PSI. Upon request, FIFFCO can supply the FS101 rated at 175 PSI, 200 PSI, or 262 PSI to meet specific project requirements.
Q3: Which flange standards does the FS101 support?
The FS101 supports EN1092-2 PN10 and PN16 (European standard) as well as ANSI B16.1 Class 125 and Class 150 (American standard). This dual compatibility makes it suitable for international projects with mixed piping systems.
Q4: How often should an OS&Y gate valve be inspected?
According to NFPA 25 (Standard for Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems), OS&Y gate valves should be visually inspected weekly to confirm they are in the open position, and fully exercised (opened and closed) annually.
Q5: What is the temperature range the FS101 can handle?
The FS101 operates reliably between 0°C and 80°C, covering most indoor fire suppression environments as well as moderate outdoor climates.
The FIFFCO Standard OS & Y Gate Valve FS101 delivers what fire protection systems demand most: proven pressure performance, durable materials, and a design that makes inspection effortless.
Whether you’re specifying valves for a new build, retrofitting an existing fire suppression system, or sourcing replacements, the FS101 gives you the confidence that comes from a product engineered specifically for life-safety applications.
Ensure total safety with FIFFCO. Contact us today for a quote on our Standard OS & Y Gate Valve FS101 — and let our technical team help you find the right specification for your project.