(1) Vent valve. (2) Drain valve.
Some engines have a water separator. The water separator is installed between the fuel tank and the rest of the fuel system. For efficiency in the action of the water separator the fuel flow must come directly from the fuel tank and through the water separator. This is because the action of going through a pump or valves before the water separator lowers the efficiency of the water separator.
The water separator can remove 95 percent of the water in a fuel flow of up to 125 liter/hr (33 gph) if the concentration of the water in the fuel is 10 percent or less. It is important to check the water level in the water separator frequently. The maximum amount of water which the water separator can hold is 0.4 liter (0.8 pt). At this point the water fills the glass to 3/4 full. Do not let the water separator exceed this water volume before draining
Drain the water from the water separator every day or when the water level gets to 1/2 full. This gives the system protection from water in the fuel. If the fuel has a high concentration of water, or if the flow rate of fuel through the water separator is high, the water separator fills with water faster and must be drained more often. To drain the water separator, open drain valve (2) in the drain line and vent valve (1) at the top of the water separator. Let the water drain until it is all out of the water separator. Close both valves.