Optionally, a pressure sensor may be placed on the output side of {HEAD ~ the pump} to provide {TAIL ~ an indication} of an empty reservoir or a substantial blockage in the distribution system  
to provide
Optionally , a pressure sensor may be placed on the output side of { HEAD ~ the pump } to provide { TAIL ~ an indication } of an empty reservoir or a substantial blockage in the distribution system
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 OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH