What Causes Water Contamination in Fuel Tanks?

Water is one of the biggest threats to fuel quality. Many sites don’t realise there’s a problem until equipment starts failing.

Water contamination can reduce fuel quality, encourage microbial growth (“diesel bug”), accelerate corrosion and lead to blocked filters, damaged pumps and costly downtime.

The most common causes include:

Condensation: Temperature changes cause moisture to form inside partially filled tanks. Over time, this condensation settles at the bottom of the tank.

Damaged tank seals or vents: Worn seals, damaged inspection covers or poorly maintained vents can allow rainwater to enter the tank.

Contaminated fuel deliveries: Although uncommon, water can occasionally be introduced during fuel deliveries if contamination exists within the supply chain or delivery equipment.

Poor maintenance: Without regular inspections and water checks, even small amounts of water can accumulate unnoticed for months or years.

Microbial contamination: Where water and diesel meet, bacteria and fungi can grow rapidly, producing sludge that blocks filters, corrodes tanks and damages fuel systems.

How can you prevent it?

✔ Regular fuel sampling

✔ Routine water checks

✔ Tank inspections

✔ Tank cleaning when required

✔ Maintaining vents, seals and associated equipment

Preventative maintenance is significantly more cost-effective than dealing with contaminated fuel, damaged equipment or an environmental incident.

If you’re unsure about the condition of your fuel storage system, BMS Group can help assess, inspect and maintain your assets. Get in touch with us for specialists advice or a quote, call 0345 230 7887 or email sales@bms-ltd.com.