Closure of the first valve apparatus prevents fluid communication along the first flow path, whereby {HEAD ~ fluid communication} may be diverted to {TAIL ~ the second flow path}, provided the second valve apparatus is in an open configuration 
Closure of the first valve apparatus prevents fluid communication along the first flow path , whereby { HEAD ~ fluid communication } may be diverted to { TAIL ~ the second flow path } , provided the second valve apparatus is in an open configuration
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH