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