The apparatus further comprises an electrical circuit that automatically shuts off power to the liquid reservoir pump whenever the drain becomes obstructed, while energizing the pressure pump and opening the valve to permit the generation of positive pressure into {HEAD ~ the drain} to dislodge {TAIL ~ the obstruction} 
to dislodge
The apparatus further comprises an electrical circuit that automatically shuts off power to the liquid reservoir pump whenever the drain becomes obstructed , while energizing the pressure pump and opening the valve to permit the generation of positive pressure into { HEAD ~ the drain } to dislodge { TAIL ~ the obstruction }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL