Multi-tank indirect liquid level measurement system and method for holding tanks in a recreational vehicle

An apparatus for indicating the depth of a liquid in a plurality of tanks, wherein:

• the apparatus comprises an air pump, a pressure indicating device, a pressure switch, a tank selection unit, and a user-operated electrical switch that are organized into an air tube system and an electrical circuit;
• the air tube system is configured for selectively and pneumatically communicating air pressure between:
• a bottom of a tank selected from the plurality of tanks;
• the pump, wherein the pump further comprises an electrically-powered air pump;
• the pressure switch;
• and
• the pressure indicating device;
• the tank selection unit comprises a multi-port plug;
• the multi-port plug comprises:
• a plurality of outlet ports configured for connection to a plurality of air lines that are configured for pressure communication with the bottoms of the plurality of tanks;
• and
• at least one pressure relief hole configured for equalizing the pressure inside the system to atmospheric pressure when an outlet port of port selector is rotated from a position aligned with a first outlet port of the multi-port plug to a position aligned with a second outlet port of the multi-port plug;
• and
• the electrical circuit comprises:
• an electrical current source configured for powering the pump;
• a manual switch configured for manually turning the pump on and off;
• and
• the pressure switch, wherein the pressure switch is configured for turning off the pump when the pressure in the air tube system exceeds a threshold value.

A method for measuring the depth of liquid in a plurality of tanks, wherein:

• the method comprises providing an air pump, a plurality of air tubes, a user-actuated electrical switch, a pressure switch, a tank selection unit, a pressure indicating device, and a battery, wherein:
• the tank selection unit comprises a tank selection unit housing and a selection knob;
• and
• the selection knob is retained inside a cylindrical interior of the tank selection unit housing by a retainer clip that engages with the cylindrical interior of the tank selection unit housing;
• placing one end of each of the plurality of air tubes in the bottoms of each of the plurality of tanks;
• putting the other end of each of the plurality of air tubes in pressure communication with the outlet of the air pump, the pressure indicating device, and the pressure switch;
• using the battery to start powering the air pump when the user-actuated electrical switch is closed and to stop powering the air pump when the pressure switch responds to a threshold pressure;
• using the pressure indicating device to read the pressure of the air in at least one of the air tubes.