An apparatus for use in a septic system such as an aerobic wastewater treatment plant connected to a drip irrigation system for dispensing wastewater from the septic system. The apparatus includes a pump having a pump outlet for a pumping treated wastewater from the septic system, a filter connected to the pump outlet, the filter having a first output for directing filtered water to the drip irrigation system and a second outlet for disposal of backwash water used to clean the filter. There is an accumulator or canister having a predetermined volume for receiving water from at least one of the drip irrigation systems and the second output of the filter. The accumulator has an outlet connected to a pressure actuated normally open flush valve, which closes in response to pressure from water in the accumulator and which moves to the normally open position when the pump is deactivated.