The moisture ejector valve is optional.

The valve automatically drains moisture and contaminants from the air reservoir. It mounts to the reservoir at the valve supply port with the exhaust port pointing down.

The supply and the exhaust ports are normally closed. When the air compressor turns on to increase reservoir pressure, the supply port opens. This allows air and contaminants to collect in the sump of the moisture ejector valve. The supply port remains open until the reservoir pressure reaches the governor cut-out pressure. The valve spring then closes the supply port.

When the air reservoir pressure drops about 14 kPa (2 psi), the sump cavity pressure opens the exhaust port and ejects the moisture and contaminants. The exhaust port remains open until the sump pressure is exhausted. The length of time the exhaust port remains open and the amount of moisture and contaminants ejected depends on the sump pressure and the reservoir pressure drop.

The valve can be operated manually by pushing a wire up the exhaust port. Remove the wire when draining is complete.