The ET109-001 reverse osmosis water filter drain adapter is designed to connect discharge line from a RO filter to the drain. The ET109-001 converts the plumbing of a single sink with garbage disposal to receive the reject water from an under-counter reverse osmosis appliance or a distillation system which has an automatic backwash feature. The ET109-001 is most commonly used in condominiums, apartments, and cottages and is preferred way to connect RO system to the drain line. The ET109-001 eliminates gurgling sound and provides a safe and effective way to comply with local plumbing codes. The ET109-001 reverse osmosis drain adapter is listed by UPC and tested for compliance with IPC and NSF standards.