US Patent 9908122 Waste fluid holding tank drain system and method

A waste fluid containment and draining system may have a black waste water holding structure for holding black waste water and a grey waste water holding structure for holding grey waste water. First and second valves may be included for enabling selective emptying of the two holding structures. A macerator pump may be used which has an input in flow communication with both of the first and second valves. A discharge conduit may be in flow communication with an output of the macerator pump. A control subsystem may be in communication with the first and second valves and the macerator pump for controlling the first and second valves, together with the macerator pump, to enable selective pumping out of the holding structures by the macerator pump through the discharge conduit.