Oxygen dissolved in the water would normally be less than 8 pm and {HEAD ~ a manually selected ratio} assuming 8 ppm would be adequate for {TAIL ~ smaller installations} 
adequate for
Oxygen dissolved in the water would normally be less than 8 pm and { HEAD ~ a manually selected ratio } assuming 8 ppm would be adequate for { TAIL ~ smaller installations }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL