77 Ill. Adm. Code 890.760
Pressure Type Water Treatment Units
Section 890
Section 890.760 Pressure
Type Water Treatment Units
Wash water and rinse water drain
lines from water softeners and other types of water treatment units shall
discharge through a vertical air gap at least twice the diameter of the pipe,
but not less than two (2) inches. Any water softening unit which depends on a
venturi created by the flow of water from the water supply line to the
softener, for the purpose of siphoning brine solution for regeneration, shall
not be required to have a backflow preventer on the water supply line. All
other types (those that depend on internal check valves to prevent backflow
and/or have the inlet supply of water stopped during regeneration) shall have a
double check valve backflow preventer assembly installed on the inlet water
supply line.