Diesel fuel filters use a connected water separator to remove water from the fuel before it enters the vehicle's fuel injection system. The water collects in a small tank located below the fuel filter. In time, the water collection tank fills to a point where the water separator does not adequately remove any more water from the fuel. Emptying the water collection tank on a regular basis ensures the fuel filter performs properly and keeps corrosion causing water from entering the vehicle's fuel injection system.
Open the bonnet of your vehicle. Look along the vehicle's firewall to find the fuel filter.
Hold a plastic container under the valve located at the base of the fuel filter.
Turn the nut located on the valve counterclockwise to start draining the water from the fuel filter. Turn the valve nut with a pair of pliers if it will not turn by hand.
Turn the valve nut clockwise to close the valve when all water has drained from the fuel filter. Wipe any spilt water from the area around the fuel filter with a rag.
Dispose of the drained water. Send discoloured water or water containing diesel fuel to a testing facility to diagnose potential internal engine problems.