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