DELTA M has many customers that use our switches to determine if water is present in fuel storage tanks. Several large northern city rapid transit authorities use DELTA M switches to continuously remove water from fuel storage tanks. Two switches are mounted close to the bottom of the tank with one being slightly higher than the other. As water separates from the fuel, it settles to the bottom. When the DELTA M switch mounted higher in the tank detects water, it activates a pump which pulls the water from the bottom of the tank. When fuel reaches the switch mounted closest to the bottom of the tank, the switch senses the presence of the fuel and shuts off the pump. This allows for very inexpensive automatic control.