# Why don't I see a pressure loss in downstream junctions after my TCV?

 Product(s): Bentley WaterGEMS, Bentley HAMMER, Bentley WaterCAD Version(s): 08.11.XX.XX, 10.XX.XX.XX Area: Modeling

# Problem

Why don't I see a pressure loss in downstream junctions after my TCV?

Or

Why doesn't changing the valve diameter for a TCV using a discharge coefficient effect the pressure loss?

# Solution

The pressure loss across a TCV valve is based on the discharge coefficient. If the discharge coefficient is large enough there won't be much of a loss across the valve device.

If you wanted to test this you could progressively make the discharge coefficient smaller and create a graph of the pressure loss and headloss at the valve to see how they react to the changes.

*Note that changing the valve diameter in conjunction with the discharge coefficient will not induce more headloss or pressure loss as might seem logical. The reason for this is because when you're using a discharge coefficient for a valve the diameter property is really just there for reference purposes, so you know how large the valve is. The diameter of the valve is taken into account via the discharge coefficient value.