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