Take an empty propane tank and buy the reverse thread tank valve connector and fit it to the tank. Screw a 1/4 inch T onto the reverse thread valve connector (which is 1/4 inch) and screw your 1/4 inch valve onto one end of the T. Screw the gauge into the other end of the T. Buy the necessary fittings to connect to your pump. Pull your vacuum on the propane tank (and gauge) with your Water Puppy or backwards plumed air compressor. Close the 1/4 inch valve and let it sit. You probably have most of those parts in your diddy box and if you're like me you always have one of your propane tanks empty.