US Water seems a little
US Water seems a little slow with order fulfillment, but they do have Techs available to help with issues.
My unit (as purchased) continuously had "Brine" water going down the drain. Also, the permeate Pump is very noisy, but I ultimately found out this is normal. I had to call US Water for help with wasted "Brine" water.
A Check Valve was diagnosed over the phone and would be shipped to me.
I continued online research. Some (US Water) says an Automatic Shut Off (ASO) valve is not necessary with a permeate pump. Others say that an ASO Valve is still needed. Personally, I don't see anything to stop fresh water from entering the system and going down the drain without an ASO valve. An ASO valve also helps with TDS Creep.
While waiting for parts from US Water, I fixed by adding an ASO Valve long before the check valve arrived. Installation diagrams are available on US Water's site by downloading documents AS IF you purchased a Permeate Pump by itself. Hope this helps others.