***Note, this is not something you can buy and add-on to a Jenny compressor it must be ordered when buying the compressor new.***  I don't recommend this option, but it is something we can do.  This is the pneumatic style tank drain for your Jenny Air Compressor. 

Designed For Use on All Compressors with an Unloader Port. Complete Drainage is Assured by Double Action of the Valve (which opens when the compressor starts and stops). Long, Trouble-Free Service is Provided Through Simplicity of Design and the Use of Rust-Resisting Materials.

A minimum pressure of 30 PSI is required to permit this valve to function properly. Maximum operating pressure 300 PSI. 

Valve Specs:

• Inlet Size: 3/8" NPT 
• Outlet Size: 1/4" NPT (hose barb in photo not included!)
• Pressure Rating: 30-300 PSI
• Min Temp: -40°F 
• Max Temp: 225°F