Beyond Sampling: Preventing Diesel Fuel Contamination

Routine fuel sampling and analysis are critical components of any effective fuel quality maintenance program. Fuel testing and tank inspection services are core offerings because protecting your diesel fuel from contamination protects equipment uptime and your bottom line.

Whether managing bulk fuel storage tanks, on-site diesel tanks, or off-road fuel systems, oversight and routine testing helps detect contamination before it leads to costly damage.

How Professional Fuel Sampling Works

We collect fuel samples using a cylindrical stainless-steel sampling device known as a bacon bomb or fuel thief. This tool is lowered into the tank to collect representative samples from multiple tank levels including top, middle, and bottom.

This multi-level approach is essential because fuel quality can vary significantly within the same tank. A sample taken from the top may appear clean, while contamination, especially water and microbial growth—often settles at the bottom.

Beyond Sampling:

While visible signs of contamination may sometimes be detected with the naked eye, that is not always the case. A clean and bright sample does not guarantee clean fuel. That’s why we encourage independent laboratory analysis that benchmarks results against  ASTM methods that evaluate water content, microbial activity, sediment and fuel stability.

BEYOND SAMPLING Left: A bottom sample collected shortly after a fuel delivery appears relatively clean. Right: Further inspection revealed corroded metal debris collecting on the cylindrical fuel thief stainless-steel sampling device.

Case Study: Hidden Diesel Fuel Contamination in a 10,000-Gallon Tank

During a recent inspection of a 10,000-gallon off-road diesel tank, we collected a bottom sample shortly after a fuel delivery. The fuel sample appeared relatively clean at first glance—great news for the customer.

However, further inspection revealed corroded metal debris collected on the fuel thief. The debris responded to a magnet, confirming the presence of tank corrosion.

Where there is corrosion, there is usually:

• Water contamination

• Microbial growth in fuel

• Accelerated tank deterioration

Turbulence from a recent delivery temporarily disturbed and suspended settled contaminants in the tank, but heavier corrosion particles quickly settled to the bottom, where proper sampling allowed us to detect a potential problem before it had a chance to create operational challenges.

What Causes Water and Microbial Contamination in Diesel Fuel?

Water can enter fuel storage tanks through:

• Rainwater intrusion through tank vents and unprotected fueling sites

• Condensation from humid air during fuel withdrawals

• Delivery of “wet” fuel

• Improper tank sealing or maintenance

  
  

Once water enters the tank, it creates the ideal environment for fuel microbes—bacteria and fungi commonly referred to in the industry as “bugs.” These microorganisms:

• Live in the water at the bottom of the tank

• Feed on hydrocarbons at the fuel/water interface

• Degrade rubber gaskets, O-rings, hoses, and tank linings

• Produce sludge, corrosive acids, and additional water as waste

In temperatures between 68 and 86°F, bacteria can multiply quickly. Over time, they form gel-like colonies known as biofilms, which are highly destructive. Modern ultra-low sulfur diesel (ULSD) and biodiesel blends can hold more dissolved water than older fuels, which can increase the likelihood of microbial activity in storage tanks.

The Risks of Ignoring Fuel Contamination

Unchecked microbial growth and tank corrosion will lead to:

• Premature fuel filter failures and fuel line clogging

• Corroded pumps and injectors

• Damaged tank bottoms

• Swollen hoses and connectors

• Fuel degradation

• Poor fuel economy

• Increased equipment downtime

For fleet operators, construction companies, municipalities, and agricultural operations, these issues can lead to major operational disruptions and costly repairs.

How to Treat Microbial Contamination in Fuel Tanks

If contamination is confirmed through fuel testing or laboratory analysis, corrective action may include:

1. Draining water bottoms from the tank

2. Applying a professional-grade biocide treatment

3. Polishing or filtering the treated fuel

4. Physically removing sludge or floating biofilm

5. Manual tank cleaning in severe cases

The severity of contamination determines whether polishing or filtering the treated fuel to remove dead microbial mass and suspended solids is sufficient or if full tank cleaning is required before refueling.

Preventative Fuel Maintenance: Best Practices

The most cost-effective solution to diesel fuel contamination is prevention. A proactive fuel maintenance program should include:

Draining Water Regularly

Drain water bottoms at least every six months (always before winter).

Treating Remaining Water

Use a water-soluble biocide every six months to inhibit microbial growth

Keeping Tanks Full

Maintain tanks at or near capacity to reduce condensation from moist air

Scheduling Routine Fuel Sampling

Sample tank bottoms every 3 to 4 months and conduct periodic laboratory fuel analysis

With consistent monitoring, small amounts of water can be managed before becoming microbial infestations or corrosion problems.

Protect Your Diesel Fuel Investment

Fuel contamination is preventable, but only with routine inspection, testing, and professional maintenance. Regular diesel fuel sampling, fuel tank inspection, microbial testing, and fuel polishing services can dramatically extend the life of your storage system and equipment.

Don’t wait for clogged filters or equipment failure to signal a problem; contact us to request a FREE fuel analysis.