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, the DELTA M switch mounted higher in the tank activates a pump when it detects water and it pulls the water off of the bottom of the tank. When fuel reaches the switch mounted closest to the bottom of tank it senses the presence of the fuel and shuts off the pump. This allows for very inexpensive automatic control.