How might water inadvertently get into the fuel tank?

Water can inadvertently enter the fuel tank through condensation in the fuel system due to temperature fluctuations. When the temperature of the air in the fuel tank changes, it can cause moisture to condense inside the tank. This typically occurs when warm, moist air enters the cooler tank, resulting in water droplets forming on the interior surfaces. Over time, this condensation collects, and if not managed properly, it can lead to significant amounts of water in the fuel, which can affect engine performance.

Other scenarios, while they may contribute to water contamination, do not reflect the more common and unsuspected method of water intrusion as effectively as condensation does. For example, while improper sealing of fuel caps and certain fuel handling practices can indeed allow water into the system, the gradual and often unnoticed issue of condensation is a more subtle but significant source, especially in aircraft where fuel systems are exposed to varying environmental conditions.