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