At the pressure side of the pump unit, there is a valve which opens during certain times to form {HEAD ~ a connection} between the pump and {TAIL ~ the pump station} to create a circulation 
between
At the pressure side of the pump unit , there is a valve which opens during certain times to form { HEAD ~ a connection } between the pump and { TAIL ~ the pump station } to create a circulation
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 OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH