Flow Coefficient (Cv) for the 0818 Series Gate Valves.

Flow Coefficient (Cv) for the 0818 Series Gate Valves.

The chart below provides the Flow Coefficient (Cv) for the 0818 No Lead Brass Gate Valves. Flow Coefficient (Cv) is the number of U.S. gallons that can pass through a valve when it is in the fully opened position at a pressure drop of 1 PSI. Testing is typically done by running water (specific gravity of 1.0 centistoke viscosity) at 60°F (°C) unless stated otherwise.

The Cv is used to properly size valves, so they have minimal effect on the hydraulic efficiency of your system. Flow Coefficient or Cv is one of the most important things to know for selecting the right size of valve. Flow velocity is also very important to take into consideration when selecting a valve, larger pipe is more expensive, however keeping the water velocity low is important to limit pressure losses due to friction, water hammer, and pipe movement due to water momentum changes inside the pipe. It is recommended to size piping to maintain a water velocity of 5 ft/second (1.524 LPM). Five feet per second is a threshold that is widely accepted by engineers and designers because beyond this velocity, the friction losses, danger of water hammer, and pipe movement due to water momentum changes are deemed to be too high.