Due to the unique conditions that we operate in on the inland waterways, it is good practise to consider your narrowboat diesel system as a component that requires looking after in its own right.

On-going maintenance costs need to be factored in to living costs on a narrow boat
Narrowboat diesel filter
Eliminating diesel bug from a narrow boat fuel tank is often a job for professionals

Diesel Management… Looking After The Mechanical!

Routine Maintenance

Regular filter changes will keep most debris away from your narrowboat fuel pump and injectors. When changing filters, look for discolouration, clouding or gelling.

Keeping the narrow boat fuel tank topped up reduces oxidation by limiting exposure of fuel to air. If fitted, regularly drain your water trap.

Keep on top of oil and filter changes as the mix of oil and un-burnt diesel fuel in your engine becomes highly corrosive to engine components. Blockages in oil galleries can occur in extreme cases of neglect.

At least once a year draw fuel from the base of the tank by either the tank drain plug, if fitted, of by use of a siphon tube that reaches to the bottom of the tank.

This will help in the removal of any water or debris that has collected in the bottom of the fuel tank. We would suggest a good few litres until the fuel is seen to be clean and clear. Dispose of the drawn off fuel responsibly.


Additives are available that can decrease diesel fuels susceptibility to atmospheric contamination by water. Others are available to stop microbial growth occurring and that will lower the cloud point in winter to stop diesel waxing in low temperatures. Waxing is caused by dissolved solids coming out of solution at low temperatures. This is not a desirable property in the depths of winter especially if you rely on running your canal boat engine for power generation or your heating is diesel fired.

If you see evidence of clouding or gelling in the fuel, there is a potential microbial infestation.

Liquid additives are available that will kill any microbes. Remember that the dead bugs will still cause problems. They, and all the associated debris, must be removed.

Filtration and “Polishing”

By far and away the best way of preventing bad fuel reaching the delicate narrowboat fuel system components is to fit an in-line decontamination filter.

Fitted between the tank and the fuel lift pump, a decontamination filter uses a simple reusable lifetime filter. The simple filter element is stuffed with high technology to ensure both water and undesirable particles that have formed in the diesel fuel tank never reach the fuel delivery system.

Decontamination filters will not remove diesel bug from narrow boat fuel tanks, but what they will do is to totally prevent the contamination from reaching the engine.

Kits are available to modify a decontamination filter to return cleaned fuel to the tank rather than deliver it to the engine. In this case, over a period of time, a decontamination filter can be used to “polish” or completely clean diesel in the fuel tank.

Diesel “polishing” is a service offered by companies who own industrial scale decontamination filters. Fast throughput equipment is used to remove contaminants. Often an inhibitor is dosed into the tank to help prevent future build-ups.

We have learned though, that due to the nature of diesel fuel, removal of contaminants will not prevent problems from reoccurring.

The only sure way to prevent running issues is to fit an in-line de-contaminator.


Inexpensive self-test kits are available to test for excess water, bacteria, mould and fungus. The presence of any of these contaminants can be dealt with if detected soon enough.

Diesel Management

Not what you're looking for? Try some other items within this chapter...

crick boat show 2024

(Saturday 25 to Monday 27 May 2024)


Britain's biggest inland waterways show.

Advance tickets can be ordered by phone and online until 12midday on Friday 17 May 2024. If you are planning to purchase advance tickets, we recommend that you do so well before this deadline to allow time for postal delivery.
Children 16 and under – free entry Saturday, Sunday, Monday

Trade & Preview Day – Friday 24 May 2024
Get ahead and visit The Fit Out Pontoon before everyone else on Preview Day!
Preview Day tickets are strictly limited to a maximum of 1,000 pre-booked visitors and give entry to the Show from 10am – 6pm on Friday 24 May.