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