An OS&Y Valve (outside screw & yoke) functions by opening and closing via a gate, which lowers both in and out of the valve. When the handle is turned clockwise the gate will close preventing any water from traveling through the valve. When the handle is turned counter clockwise, the gate will open allowing the water to flow through freely. The screws of the valve are held by a yolk on the outer portion of the valve, a wheel in the valve is attached to the nut which turns, allowing the shaft to lower or rise from the lower portion of the valve.
What is the key difference between an OS&Y and a Gate Valve?
OS&Y valves visibly show whether the valve is opened or closed which differs from a domestic water service where you can simply turn on the shower or sink to test its functionality. When the stem of the OS&Y is raised out of the body you know the water is on. With other gate valves, visual inspections will not determine if the valve is opened or closed.
When are OS&Y Valves Required?
OS&Y valves are required by NYC plumbing code on all water lines that provide fire protection meaning, any dedicated sprinkler line or combined water line (domestic & sprinkler in one pipe) must have one installed for new and existing projects. All domestic water lines 3″ or larger must have an OS&Y valve installed as well.
In addition to visual inspection, NYC code also requires that all handles and visual standpipe (sprinkler line) must be color coded
All valve handles must be the following:
Dedicated standpipe valve handles must be painted red
Combination standpipe valve handles must be painted yellow
Dedicated sprinkler valve handles must be painted green
If you are installing a new 2”copper main or a main smaller in size, you will be required to install the same size tap connection on the city main. This differs from a Wet Connection on a domestic water service where the tap connection would be one size smaller than the pipe. In most cases when installing a new 3” ductile iron sprinkler service or larger, you will be required to install a wet connection of equal size to the pipe unless approved plans state otherwise.
Example: A 3” ductile iron pipe would require a 3” wet connection to be connected to the city main.
The only exception to these rules would be if the contractor is making a repair to a existing 2.5” or 3” sprinkler main that was previously hooked up to a 2” tap connection. In this case the contractor would hook-up to the existing 2” tap on the city main.