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