Thus, {TAIL ~ the check valve} is between the furnace and {HEAD ~ components} 4 8 in the feed line 
Thus , { TAIL ~ the check valve } is between the furnace and { HEAD ~ components } 4 8 in the feed line
OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH