The apparatus further comprises {TAIL ~ 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 the drain to dislodge {HEAD ~ the obstruction} 
The apparatus further comprises { TAIL ~ 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 the drain to dislodge { HEAD ~ the obstruction }
OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL 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