The forged brass valve body has a full port 7/16" drain orifice. This large orifice virtually eliminates clogging by rust, scale, or other air system debris and can discharge more than two gallons of condensate per drain opening at 100 psig. It is recommended the use of a strainer in front of any diaphragm valve. The valve does have a large orifice, but the diaphragm needs to be protected.
This is a diaphragm and its function is to lift up to expose a large orifice. If the bleed orifice in the diaphragm clogs then the diaphragm will not lift up, the valve is deemed blocked, and stays closed.