Take a sample from the fuel tank into a clean container. Allow the sample to “settle” and any water to accumulate at the bottom of the sampling container. Ideally, the sample should be drawn from the tank sump or lowest point from a water drain point. Alternatively, draw a tank bottom sample using a dipped sample tube from the tank fill aperture. For vehicle tank testing, if it is impossible to harvest a tank bottom sample then the contents of the primary fuel filter is the next best place. This sample however may not represent the tank bottom. Any sample taken should be tested as soon as possible after collecting and, in any event within 6 hours to maintain the integrity of the sample.
NOTE : When possible, test the water phase of the sample taken from the fuel tank. Testing the water phase will provide more accurate results than testing the fuel phase.