What does cv rating mean on a water valve?

Answer 1

The CV value is the flow rate required to generate 1 psid of pressure loss through the valve. Since pressure drop follows a basic square law the relationship between Cv, flow and pressure loss is as follows:

DP = k x Flow^2 eq 1

Where k is a constant that represents the flow shape in the wide open condition.

Since Cv is the flow rate at 1 psi of pressure loss then it follows that

DP = k x Cv^2 = 1 eq 2

solving for k from eq 2 yields

k = 1/Cv^2 eq 3

substituting eq 3 into eq 1 yields

DP = (Flow/Cv)^2

Now you have an equation that will tell you the pressure and flow relationship for that particular valve with a particular fully open Cv value.

In short, the higher the Cv value the more flow the valve will allow for the same pressure loss or the less pressure loss for the same flow.

Good luck