|(a) Water treatment equipment is defined as an appliance, which includes water softeners and reverse osmosis systems, used to: (1) alter the mineral content of water; (2) alter the microbiological content of water; (3) alter other substances found in water; or (4) purify water. (b) Back flush or discharge from water treatment equipment installed on or after September 1, 2003, may be discharged into an on-site sewage facility (OSSF) as provided in this subsection. (1) Water softener. (A) The water softener must regenerate using a demand-initiated regeneration (DIR) control device. The water softener must be clearly labeled as being equipped with a DIR control device as follows: (i) the label shall be affixed to the outside of the water softener so the label can be easily inspected and read; and (ii) the label shall provide the name of the company that installed the water softener. (B) A water softener may be connected to an OSSF with a non-standard or proprietary treatment system only as described in §285.32(c) and (d) of this title (relating to Criteria for Sewage Treatment Systems) if the water softener drain line: (i) bypasses the treatment system; and (ii) connects directly to a pump tank if the OSSF has a pump tank or directly to the pipe between the treatment system and the disposal system if no pump tank exists. (C) An owner may continue to use a water softener that discharges to an OSSF and does not meet the requirements of subparagraph (A) of this paragraph if the water softener was installed before September 1, 2003. An owner must replace any water softener installed before September 1, 2003, with a water softener that meets the requirements of subparagraphs (A) and (B) of this paragraph at such time as: (i) an owner replaces the existing water softener; or (ii) an owner or installer installs, alters, constructs, or repairs an OSSF for the structure or property served by the existing water softener. (2) Reverse osmosis system. (A) Point-of-use (under sink unit) reverse osmosis systems. The back flush from a point-of-use reverse osmosis system may be discharged into an OSSF without including calculations of the back flush water volume in the OSSF planning materials. (B) Point-of-entry (whole house unit) reverse osmosis systems. The back flush from a point-of-entry reverse osmosis system may be discharged into an OSSF if: (i) the owner can demonstrate that the point-of-entry reverse osmosis system does not cause hydraulic overloading of the OSSF; or (ii) the water volume from the point-of-entry reverse osmosis system is accounted for (added to the usage rate in §285.91(3) of this title (relating to Tables)) by providing calculations of the increase in wastewater volume with the OSSF planning materials. (3) Water treatment equipment other than water softeners and reverse osmosis systems. If an owner uses water treatment equipment other than water softeners or reverse osmosis systems, the back flush from the water treatment equipment may be discharged into an OSSF if the water volume is added to the OSSF usage rate in §285.91(3) of this title. This water volume calculation must be provided with the OSSF planning materials. (c) Discharges from all water treatment equipment shall enter the OSSF system through an airgap or an airgap device as required in the Uniform Plumbing Code (2000).