Diesel and water Don’t Mix. Here’s How to Fix It

April 1, 2024 | By Wendall Stroderd, Tank Wizards

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Diesel and water Don’t Mix. Here’s How to Fix It

Some things — like bread and butter — go well together, while others — like diesel and water — not so much.

The combination of the latter two can spell major headaches for owners of diesel tanks and accompanying equipment. The big problem is that diesel attracts water, literally. Like Romeo and Juliet, it’s almost impossible to keep these two apart, thanks to diesel’s hygroscopic qualities, which absorbs moisture from the air at a molecular level. Unfortunately, this can be a fatal attraction for fuel tanks, filters and engines, because water in diesel fuel makes a perfect breeding ground for bacteria and microbes, which multiply rapidly, forming acids that rust and corrode tanks and clog fuel filters.

Water connects with diesel during transit, storage or handling. It can sneak in through fuel delivery from a supplier, through leaks into a tank caused by pressure washing, rain or even ground water, from humidity and condensation in a tank and through broken seals or unprotected vents.

While the best amount of water to have in a diesel fuel tank is zero, it is not realistic to expect that, given all diesel contains some water. Keeping it as low as possible is the trick. When the amount of water reaches saturation point, the excess becomes free water. Free water separates from the fuel and settles to the bottom, where it becomes a home for rust-inducing bacteria. Suspended water is miniscule water droplets that remain suspended in stored fuels. Emulsified water is another problem altogether and a topic for future discussion. At this stage, corrective measures must address both removing the water in the tank and killing the bacteria.

Warmer climes like Florida’s have many benefits, but for diesel tank owners, one of the disadvantages is that we have extremely high humidity, which also plays a big part in the picture. When it is warm outside, condensation will form over extended periods, providing a chance for this “sweat” of water to enter a tank and create more free water. The relative humidity in diesel also tries to replicate the relative humidity in the air as moisture in the diesel is released back into the dry air so it is eventually as dry as the air. If the air is humid, you could say the diesel fuel has no incentive to become dry.

Testing for free water in a tank bottom can be accomplished by dipping the tank with a long dip stick covered with special indicator paste. Water monitors that measure free water are also a reliable method of measuring water content. This method can provide specifics on the amount of free water in the tank.

Good diesel fuel management depends on minimizing water content and prohibiting free water from forming. Treating diesel fuel with demulsifiers and NOT water-dispersing fuel additives is advisable when the water is still within acceptable levels. If diesel reaches saturation point, free water will form and then the only option is to drain/remove the water, clean the tank interior and remove any rust and corrosion. The fuel should be treated with a broad spectrum microbicide and then “polished” to remove microbial and other contamination. Neither tank cleaning or fuel polishing are DIY jobs, since both require the expertise and equipment of professionals.

Meet Our Thought Leader

Wendall Stroderd is president of Tank Wizards, a Brevard County-based company that for more than 20 years served Florida, Georgia, Mississippi, Louisiana and South Carolina with fuel tank cleaning, diesel fuel polishing and related services.

For more information, visit tankwizards.com or call 321-285-8878.