[Brad Townsend]

While waiting for the new check valve to arrive I disconnected the compressor line from the current check valve and ran the 110 compressor and sure enough air was passing out the check valve instead of going into the dryer. I removed the old check valve and pulled it apart and cleaned it and got it to work, reinstalled it and ran the main engine and got the tank up to pressure shut the engine off and the air pressure still dropped. There is no check valve where the 110 compressor line elbows into the dryer line but I did replace the check valve at the 110 compressor. Seems the only reason for a check valve between the compressor and the dryer is so the 110 compressor would not back feed to the main engine compressor but to go through the dryer.  So the wet tank has a check valve on it and there is a check valve between the engine compressor and the dryer, even if there was no check valve between the engine and the dryer the new check valve at the wet tank should hold the air from back feeding so seems to me the leak is some where else. 
On the wet tank there is a small 1/4 inch line on the end of the tank drivers side that goes up over the frame maybe to tag axle air bag? And there is another heavy line on top of the tank on the passenger side, not sure where it goes.
On the bottom of the wet tank is a Bendix D-2 automatic drain valve, I sprayed with bubble stuff and it seemed to be ok. 

When the air pressure drops to where the 110 compressor comes on, the compressor will bring the pressure up in pretty good time so it seems to be working as should.