I have a new ro unit from aqua safe there is a threaded fitting on the top that my supply line goes in from the ro and out to faucet fitting. On the side of the tank there is something with a little blue plastic cover over it. What is the thing on the side? And should it feel like it turns freely? 
Any insite appreciated I want to start hooking up. Curt
Any insite appreciated I want to start hooking up. Curt
