Condensation in the vent tube can damage the electronics in your sensor, resulting in unreliable readings. 

The venting cap is a PVC tube with a hydrophobic patch that allows moisture to pass out of the tube without allowing water in.  The cap is sealed by an o-ring and is easily installed in the field.
APG Gore Patch Filter, Terminating Vent Tube for PT-500
  • APG Gore Patch Filter with Terminating Vent Tube for PT-500 Submersible Pressure Transducer