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