The Terminator T-2000 automatic shut off valve for reverse osmosis system. The Terminator 2000 will monitor the tap water pressure and the purified tank pressure. As the tank fills to about 2/3 of the tap water pressure, the Terminator will turn the system off. This can save as much as 1,500 gallons of water per month when compared to a system without a valve. The system is designed to turn back on after a significant amount of purified water has been drawn from the holding tank. This feature helps reduce TDS Creep (artificial increase of TDS in the holding tank) which is caused by rapidly turning on and off RO systems. The Terminator can be installed in a vertical or horizontal position. The valve uses 1/8 inch FPT ports, allowing you to use OE or 3/8 inch tubing Installation: 1. Pre-filtered tap water goes into port #1 on the end. 2. This water then comes out port #2 and goes to the inlet side of the RO membrane housing. 3. Purified RO water must pass by port #3. Put a T or an L fitting here