Water and Draining Fuel Filters

The Filter Guys

Most primary fuel filters have drains that allow the operator to drain the water that has been separated by the filter. The frequency with which the primary fuel filter needs to be drained is ultimately dependent on the quality of fuel that is being used. Most OEMs recommend draining your water separator daily. It is also recommended to pay attention to how much water is removed at each drain and adjust the frequency of servicing accordingly.

Why Remove Water in Fuel?

Water in fuel can prematurely wear and oxidize the steel components within the fuel injectors, leading to:

  • Rusting and corrosion of components
  • Governor/metering component failure
  • Sticky metering components (both pump and nozzle)
  • Injection component wear and seizure

Free or emulsified water must be removed from the fuel to prevent corrosion and damage to the fuel system. Fuel additives may claim they remove water, when really they dissolve the water. Which in turn, will pass through the filter and enter fuel injectors.

Types of water contamination in diesel fuel:

1) Emulsified water: water suspended in the fuel

2) Free water: water separated from the fuel and generally collected at the bottom of the fuel or the fuel storage tank

3) Dissolved water: water chemically dissolved in the fuel

Maintenance Recommendations & Guidelines

  • Drain water from your primary filter daily when refueling
  • Carry a spare set of fuel filters in case you receive a “bad” load of fuel
  • Never switch to more open filter to get longer filter life, you are trading away fuel pump and injector life
  • Never use fuel to lube the gasket. Fuel isn’t as slick as oil and if you use fuel it could cause gaskets to bunch or pinch when it is tightened, causing the filter to leak.

If using biodiesel:

  • make sure your fuel supplier meets current fuel standards
  • make sure your engine is compatible with the concentration (or percent) biodiesel you wish to use
  • When using your own fuel storage tank, remember that removing contaminants before they reach the vehicle is the best practice. Ensure you have effective bulk storage tank filtration.