Water in Your Fuel Tank: The Most Expensive Problem You Can't See

When facility managers think about fuel system failures, they often focus on pumps, filters, generators, or mechanical equipment. Yet one of the most costly and common threats to fuel system reliability is something much less visible: water.

Water contamination inside fuel storage tanks is a growing issue affecting commercial facilities, healthcare organizations, municipalities, fleet operations, and backup power systems across the country. Left untreated, even small amounts of water can lead to fuel degradation, microbial contamination, equipment damage, and unexpected downtime.

The problem is that most facility operators do not realize water is present until performance issues begin to appear.

By then, the damage may already be underway.

How Water Gets Into Fuel Tanks

Many people assume water enters fuel tanks through obvious leaks or equipment failures. While this can happen, most water contamination develops gradually through everyday operating conditions.

One of the most common sources is condensation.

As temperatures fluctuate, air inside the tank expands and contracts. Moisture in that air condenses into water droplets that eventually settle at the bottom of the tank. Over time, these small amounts accumulate into a significant problem.

Other common sources include:

• Damaged tank lids or seals

• Improperly maintained sump systems

• Faulty spill containment equipment

• Fuel deliveries containing moisture

• Aging infrastructure

• Stormwater intrusion

Because water is heavier than diesel fuel, it settles at the bottom of the tank where contamination problems begin.

Why Water Is Such a Serious Problem

Water itself is harmful, but the secondary effects are often far more damaging.

Once water accumulates inside a tank, it creates an environment that supports microbial growth. Bacteria and fungi thrive at the fuel-water interface, feeding on fuel components and creating contamination that spreads throughout the system.

Over time, this can lead to:

• Fuel degradation

• Microbial contamination

• Biofilm formation

• Sludge accumulation

• Corrosion of tank surfaces

• Clogged fuel filters

• Injector damage

• Reduced fuel quality

For generators and critical infrastructure, these issues can significantly impact reliability.

The Hidden Cost of Water Contamination

Fuel contamination often develops slowly, making it easy to overlook during routine operations.

Many facilities continue operating without realizing that water is actively degrading fuel quality and damaging equipment.

The financial impact can include:

• Increased maintenance costs

• Frequent filter replacements

• Fuel disposal expenses

• Emergency service calls

• Generator failures

• Equipment repairs

• Reduced fuel lifespan

As fuel prices continue to rise, every gallon lost to contamination becomes more expensive.

Water contamination is not simply a maintenance issue, it is an operational and financial risk.

Why Backup Generators Are Especially Vulnerable

Generator systems are particularly susceptible to water-related fuel problems because fuel often remains in storage for extended periods.

Unlike fleet fueling systems that cycle fuel regularly, generator fuel may sit for months or years before being used.

This creates ideal conditions for:

• Condensation buildup

• Water accumulation

• Fuel oxidation

• Microbial growth

Many generator failures that occur during emergency situations can ultimately be traced back to fuel quality issues rather than mechanical failures.

A generator can be perfectly maintained and still fail if the fuel inside the tank is contaminated.

The Connection Between Water and Microbial Contamination

One of the fastest-growing concerns in the fuel industry is microbial contamination, sometimes referred to as "diesel bug."

Microorganisms require water to survive. Once water enters the tank, bacteria and fungi begin multiplying at the interface between the water and fuel.

These microbes produce a slimy biofilm that adheres to tank walls and bottoms. Over time, this contamination creates sludge deposits that can clog filters, foul injectors, and continuously contaminate otherwise clean fuel.

This is one reason facilities often experience recurring contamination problems despite changing filters or conducting routine maintenance.

The source of the problem remains inside the tank.

How Fuel Polishing Helps

Professional fuel polishing is one of the most effective methods for restoring fuel quality and removing contaminants from stored fuel.

The process typically removes:

• Water

• Sediment

• Particulate matter

• Microbial contamination

• Fuel degradation byproducts

Fuel polishing helps restore fuel quality while improving system reliability and reducing the risk of equipment failures.

However, in cases where microbial sludge has attached itself to tank surfaces, additional treatment and cleaning may be necessary to fully eliminate contamination.

The Importance of Preventive Maintenance

The best way to manage water contamination is to identify and address it before problems develop.

Regular inspections, fuel testing, and fuel quality assessments allow facilities to detect water intrusion early and take corrective action before contamination spreads.

Proactive fuel maintenance can help organizations:

• Protect fuel investments

• Extend equipment life

• Improve generator reliability

• Reduce maintenance expenses

• Minimize operational downtime

For facilities that depend on backup power or uninterrupted operations, these benefits can be significant.

Why Don Wood Inc.

At Don Wood Inc., we help facilities identify and eliminate fuel contamination before it becomes a costly problem.

Our services include:

• Fuel polishing

• Fuel quality assessments

• Tank cleaning

• Microbial contamination treatment

• Generator fuel maintenance

• Fuel system inspections

Our team understands the challenges associated with long-term fuel storage and provides practical solutions designed to improve reliability and protect critical infrastructure.

Final Thoughts

Water contamination is one of the most common, and expensive, fuel system problems affecting facilities today.

What begins as a small amount of moisture inside a tank can eventually lead to microbial contamination, equipment failures, fuel degradation, and costly downtime.

The good news is that these issues are largely preventable through proper fuel maintenance, fuel polishing, and routine inspections.

If your facility relies on stored fuel, understanding what is happening inside your tank is one of the most important steps you can take to protect your operation.

Contact Don Wood Inc. to learn more about fuel polishing, fuel quality testing, and fuel system maintenance services.

Frequently Asked Questions

What causes water in a diesel fuel tank?

Water can enter fuel tanks through condensation, damaged seals, sump failures, stormwater intrusion, or contaminated fuel deliveries.

How do I know if there is water in my fuel tank?

Common signs include cloudy fuel, microbial growth, clogged filters, corrosion, generator performance issues, and recurring fuel contamination.

Can water damage a generator?

Yes. Water contamination can lead to fuel degradation, microbial growth, clogged filters, injector damage, and generator failures.

What is microbial contamination in diesel fuel?

Microbial contamination occurs when bacteria and fungi grow inside fuel tanks, typically at the fuel-water interface. These microorganisms create sludge and biofilm that contaminate fuel systems.

Does fuel polishing remove water from diesel fuel?

Yes. Professional fuel polishing systems are designed to remove water, sediment, and other contaminants from stored fuel.

How often should fuel tanks be tested for contamination?

Facilities with backup generators or long-term fuel storage should conduct routine fuel testing and inspections as part of a preventive maintenance program.

What are the benefits of fuel polishing?

Fuel polishing improves fuel quality, removes contaminants, reduces equipment wear, extends fuel life, and helps ensure reliable system performance.

Why is water contamination becoming a bigger problem today?

Modern fuel formulations, biodiesel blends, longer fuel storage periods, and aging infrastructure have increased the likelihood of water-related fuel quality issues.