Wow Russ thanks for those labeled pics like that. Helps a bunch! I was getting confused because what I thought was the flow restrictor is actually the check valve. I went on the BRS site to see what a flow restrictor looked like and it looked like that. However, upon further inspection they do look a bit different. Im not home yet, but I will double check and make sure that line has a flow restrictor inside it. On that note, is there any important difference between the "inside the tubing" flow restrictors and those that sit on the outside?
Also, the unit I was using previously was this coral life pur flo 2.
http://www.amazon.com/Coralife-05692-Pure-Flo-50-Gallon-System/dp/B0006JKO9W. I was thinking about switching the membrane housings on the units just because the housing on this unit is kind of crummy looking (I didn't notice any leaks but I forgot to ask why the housing was taped up when I purchased). Just want to make sure, this shouldn't be a problem since both the 50 gpd and 75 gpd membranes are 1812 membranes, right?
edit: actually I just realized that the coral life pur flo 2 unit has those J screw on fittings..not sure if that would be a problem. May just buy another housing...