It consists of a tire valve on one end with a pipe thread on the other plus a blanking cap for the fuel fitting. The fitting screws into the tank drain and is used to gently pressurize the tank with a bicycle pump after first taping a party balloon to the vent fitting.
The procedure is to pump up the tank until the balloon inflates. It should stay inflated if there are no leaks. While the tank is pressurized you brush the joints and seams with soapy water. Any small leaks will generate bubbles in the soap solution. Ignore bubbles/leaks around the filler cap and the balloon since they are hard to seal.
The balloon acts as a safety valve and an indicator. Some people instead use a clear plastic tube formed in to a U shape and filled with water to form a manometer. Again pressurize the tank until there is a change in the height of the water on either leg of the U. It shouldn't vary if there are no leaks.
DON'T USE COMPRESSED AIR - you could easily blow the tank!
Jim Sharkey
Fuel Tank Testing
Linear Mode
