A battery operated flush assembly for a portable toilet. The flush assembly includes a pump and motor mounted to the toilet's seat section. A battery pack is removably mounted to the seat section and includes terminals which, as a result of mounting, become coupled to the motor. The battery pack supplies electrical power to the motor and includes an actuator, protected from inadvertent actuation within a recess, for electrically closing the electrical circuit and causing operation of the pump to discharge flush water into the bowl. A check valve, located in-line with the discharged flush water, opens in response to the pumping of flush water and is maintained open with minimal line pressure to increase the life of the battery pack. An O-ring is also used to ensure that the battery pack can be easily removed and reinstalled with a fluid tight seal therearound.