Diagnosis of diesel bug contamination

Diesel Bug Tank Cleaning – The Tank Doctors

19.06.2026

The WaterSports editorial team spoke with two tank cleaning experts – Hans Joachim Burmester, owner of MFT Mikrofiltertechnik based in Geesthacht near Hamburg, and his son Christian – about the problem of diesel contamination. When only a complete overhaul through tank cleaning can help, Hans Joachim and Christian Burmester from MFT Mikrofiltertechnik first begin by inspecting the tank using a handheld camera, which allows them to look into many corners of even small, complexly installed tanks.

Why is an inspection hatch on a tank important?

Here, the experts can assess what the inside of the tank looks like.

Of course, access via an inspection hatch is required. Unfortunately, this is not always standard, which is why the specialists at MFT Mikrofiltertechnik also offer on-site systems to retrofit such an opening.

This then enables yacht owners to maintain their tank in the future. If contamination is detected, the fuel must be pumped out and temporarily stored.

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Are any upgrades necessary?

“Ultimately, it is about protecting the system from residues settling in the lines and in the engine’s injection system.”
There is often a need for retrofitting at the connections of the supply and return lines of the tanks. “When you are already working on the system, you should do things properly and thoroughly right away,” explains Burmester.

Should copper fuel lines be replaced with stainless steel lines?

It is recommended to redesign the connections and integrate the lines directly into the inspection hatch to ensure easy access in the future.
Copper lines should be replaced with stainless steel, as copper promotes oxidation and is often part of the problem.
The pumped-out fuel is then finely filtered, cleaned of water and dirt particles, and returned to the tank.

Is there a need for retrofitting?

After cleaning, post-treatment is crucial: in cases of contamination or engine failure, residues or microorganisms may also be present in the fuel system. Experts recommend a specific additive (e.g. from Deutz).
After a shock dosage of 1 litre to 200 litres of fuel, the engine should run for three to four hours to dissolve deposits.

How can future contamination be prevented?

The product cleans injection components, dissolves deposits, and restores engine performance as well as exhaust behavior.
After cleaning, prevention is crucial: additives from Tunap, ERC, or Grotamar prevent the formation of microorganisms in the fuel but must be used regularly and at an early stage.
In cases of severe contamination or advanced degradation, a complex tank cleaning remains the only solution.