Leak Testing the Tanks   September 6th, 2009

The last step in building the fuel tanks is to test them for leaks. This is done by pressurizing them to about 1psi and making sure they are airtight.
The tanks have a total of four openings:
1. Fuel Cap
2. Fuel drain
3. Fuel pickup tube
4. Vent Line
I installed the fuel cap with a latex glove to make sure it was airtight. I also capped the main fuel pickup line, and installed a bicycle-style stem on the fuel drain. I left the fuel drain line open.
There are two ways to pressure test the tank. One is to hook up a balloon to the fuel vent line, and inflate it through the fuel drain. You then make sure the balloon doesn’t deflate after a few days. The problem here is that you have to compensate the expected diameter of the balloon for any temperature changes. This sounded difficult.
The other way to do this test is to connect a clear plastic hose to the fuel vent line, and pour some water in it to form a water column (making sure the water doesn’t go into the tank!). This also requires compensating for temperature changes, but I figured it’d be a lot easier to accurately measure the distance between two water levels than a balloon diameter. So, I got me some clear hose from Home Depot (they have them in the plumbing section) and used food coloring to dye some water for my test. I then mounted the tank up high on two special platforms and used my little bicycle pump to get about 27″ of water (~1psi). I installed an old thermostat nearby, and I would check the temperature two or three times a day, as well as the water level.
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