RO drain question

[barne35228]

I have a Watts Premier 4 stage under sink RO system with an air gap faucet. When I disconnect the RO faucet drain tube from the drain saddle, the water from the drain tube flows continuously. The system makes a noise that sounds like water is constantly running (not loud, but loud enough to hear). Is it normal for a constant flow of water to be running down the drain tube?

[XLXR]

RO systems produce about 4 gallons waste water to 1 gallon filtered water. The waste water flows through the RO membrane with much less resistance. There should be a pressure valve to shut off water flow when the tank is full. Maybe the pressure valve is bad, (I am not sure of the correct name). I am no expert, just trying to learn this stuff myself.