Water and microorganisms
Microorganisms can grow where water is present in stored fuel. Water can enter through damaged seals or openings, or accumulate through condensation. It can support contamination at the fuel–water interface.
Operations guide
Diesel contamination, fuel age and storage care
Understand what can affect stored diesel and how to investigate a change in fuel condition.
Practical guidance
What “diesel bug” means
The term describes microbial contamination rather than one specific organism.
Recognise a change
Repeated filter blockage, sediment or an unexplained change in fuel appearance warrants investigation. These observations are not a diagnosis: particles, water and cold-weather wax can also cause operating problems.
Separate fuel quality from stock monitoring
A tank gauge reports its configured measurement. A stock balance or bund alarm does not identify microorganisms or certify that fuel is fit for use.
Arrange appropriate sampling
Record the affected tank, delivery dates, symptoms and filter changes. Ask the fuel supplier or a competent fuel-quality specialist to specify representative sampling, testing and corrective action. Avoid improvised sampling or entering a tank.
Practical guidance
Why stock turnover matters
A large tank with low demand can retain fuel for longer than the purchasing plan suggests.
Ageing and oxidation
Fuel can change during storage as it reacts with oxygen. Temperature, contamination and the fuel formulation affect stability; there is no single safe storage period for every product and installation.
Tank breathing and condensation
Air moves through the tank’s designed venting as contents and temperature change. A compatible desiccant breather can help control moisture entering through the venting arrangement. It must suit the tank’s required airflow and operating conditions. Keep venting clear and include it in the agreed maintenance routine.
Review stock age as well as volume
Use first-in, first-out stock planning to avoid leaving older fuel unused: keep delivery dates, quantities and product details, and match replenishment to consumption. Fuel can mix in a tank, so a new delivery does not make all residual stock newly supplied fuel or guarantee a physically separate first-in, first-out flow.
Plan an action, then check it
Agree any water removal, cleaning, filtration or treatment with the relevant supplier. Use only a specified treatment and method for the diagnosed problem; monitoring alone cannot remove contamination.
Practical guidance
A useful fuel-condition record
Keep observations separate from confirmed test findings.
| Record | Detail to retain |
|---|---|
| Tank and product | Site, tank identifier, product specification and supplier. |
| Timeline | Delivery dates, stock movements, first symptom and subsequent changes. |
| Evidence | Service observations, filter findings and the specialist’s sampling/test report. |
| Action and release | Who approved the corrective work, what was completed and the criteria used to return the supply to use. |
Your site
Keep the records and the equipment working together.
Discuss your fuel installation and its support requirements with Fueltek.
