US Patent 8225819 Portable waste transfer tank

A includes a main body portion defining a waste holding chamber, a vent path extending from the waste holding chamber to atmosphere, and a float member. The float member is coupled to the tank for movement between a first position and a second position. The float member is movable from the first position to the second position in response to an increase in fluid level within the storage chamber. The vent passage remains open for venting the storage chamber when the float member is in the first position and is blocks the vent passage in the second position.