Product Description Reverse Osmosis Water Filter Automatic Shut-Off Valve with Quick-Connect fittings, 1/4" - Allows your system to turn off the water supply when the tank pressure reaches approximately 65% of the supply water pressure; - 1/4" fitting; - Easy to install, as the picture shown. The "in & out" markings are on the top of the valve. The top side of the valve is the high pressure side and the bottom side is the low pressure side. The high pressure from the filter housings goes to the "in" on the top of the valve. Then the high pressure "out" goes to the membrane housing inlet. The membrane housing low pressure outlet connects to the "in" on the bottom side of the valve. The "out" on the bottom goes to the tank. Remark: Continual drain problem can be caused by different factors, including automatic shut-off valve, check valve, flow restrictor, or tank pressure. Replacing the ASV may not help if the problem is caused by other factors. From the Manufacturer Reverse Osmosis Water Filter Automatic Shut-Off Valve with Quick-Connect fittings, 1/4" - Allows your system to turn off the water supply when the tank pressure reaches approximately 65% of the supply water pressure; - 1/4" fitting; - Easy to install, as the picture shown. The "in & out" markings are on the top of the valve. The top side of the valve is the high pressure side and the bottom side is the low pressure side. The high pressure from the filter housings goes to the "in" on the top of the valve. Then the high pressure "out" goes to the membrane housing inlet. The membrane housing low pressure outlet connects to the "in" on the bottom side of the valve. The "out" on the bottom goes to the tank. Remark: Continual drain problem can be caused by different factors, including automatic shut-off valve, check valve , flow restrictor, or tank pressure. Replacing the ASV may not help if the problem is caused by other factors.