There are three primary types of curb valves that we use in NYC.
The first valve is a mechanical joint curb valve that we use for all pipe size three inches and larger. On this type of valve we use ductile iron pipe for the installation. The installation usually requires the curb valve to be installed within 2′ of the curb line. If you did want to use a different type of material, the only change would be the gasket to assist with the pipe fitting as required.
This type of valve functions similar to other valves and requires to be turned clockwise in order to close. When the valve is closed the gate drops in the middle which is what stops the water from flowing beyond the valve.
Another type of valve is gate valve with a square nut on the top. Most commonly in NYC we use copper pipe when being installed with a this type of curb valve. The pipe requires a flare x male adapter which is connected to the copper, and then screwed into the threads of the curb valve. This valve functions by spinning the square nut clockwise to close and counter clockwise to open.
The final type of valve we use is a flared curb valve. The primary difference is that a different type of curb key is required to open the valve and the flared copper is connected directly to the body of the valve. The fittings used in a gate valve are no longer required. The best way to think about this is that the fittings are built into the valve itself.
When the valves opens and closes, there is a ball that drops down, which is different than the gate as previously discussed.