How Do You Get All the Water Out of the Fuel Tank?

Here are some essential tips for sumping and contamination prevention for rainy-weather pilots.

Meg Godlewski

Wednesday, March 04, 2026 at 09:00 AM ET

Verified

Edited By:

Travis Tingle

Knowing what kind of fuel your aircraft takes is basic pilot knowledge. [Credit: Meg Godlewski]

Key Takeaways:

Ensure fuel cap rubber gaskets are in good condition and caps are securely fastened to prevent water from entering the tanks.
Improve sumping effectiveness by gently jostling the aircraft and waiting 10 minutes for contaminants to settle before sampling, also performing this after refueling.
Sump all designated points on the aircraft, repeating until at least three clean samples are obtained if any water contamination is found.

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Question: I am a low-time pilot in a rainy part of the world. I know we’re supposed to check the fuel for contamination during the preflight inspection, but how do you make sure you get all the water contamination out of the fuel tank? A guy at my airport tells a story about the time his engine quit just after takeoff because there was water in the fuel. The airplane had been on the ramp in the rain for a few days, and he sumped it and got a clean sample, but it still happened. How do I prevent this?

Answer: I too live in a rainy part of the world, and many of the aircraft I fly are kept on the ramp. The best way to keep water from getting in the fuel tanks is to make sure the rubber gaskets on the fuel caps are in good condition and the caps on securely.