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Engineering ToolBox > Kv Diagram Water Valves
The diagram below can be used to estimate the kv values for valves in water systems.
The maximum pressure drop through a modulating regulating valve in a water flow system is estimated to 100 kPa. The flow through the valve is 5 liter/s. The kv value of a required valve can be estimated in the diagram below to ~ 20.
Note - a larger valve (with larger kv) will reduce the maximum pressure modulating span - and reduce the ability to provide stable regulating of the process. As a consequence it is quite normal that regulating valves are one or two dimensions below the dimensions of the connecting pipes.
Example - with a flow 5 liter/s the common pipe size may be in the range 3 - 4 inches (80 - 100 mm nominal). The common modulating valve size with kv ~ 20 is in the range 2 - 3 inches (50 - 80 mm nominal).