The fill pipe should go to the first prefilter. I'm presuming that all the filters have been installed. The hose from the second prefilter must go to your r/o. It goes onto the end with only 1 port. The third photo is of the other end of the r/o with 2 ports. The centre port goes to your tank via a Di vessel and that's the pure. The other pipe goes to the drain with waste water.
While producing water you should have about 60% waste water and 40% pure.
Thanks so much for the explanation Spruce , you have been helping members in this community for years. I took a closer photo of the pre-filters. It just seems to me that where it says "Fill" is where the tap water go straight into the tank. This is weird because like you said it should be connected to the pre-filters. Maybe there's a section inside the tank that stores tap water before it get send to the pre-filters? (the 2nd yellow circle)
Pretty poor to pay for a system and them not to do a walk through with you though.
Believe it or not, this is considered one of the top companies in our trade. (I won't name them)
Usually you get a red “gate valve” that is more accurate. The little yellow lever is what you’ll need to control to set the waste ratio. Don’t mess it up otherwise you’ll kill Your membrane very quickly. Adjust it to the ratio spruce said above.
Thanks so much for that piece of information, potentially saved me from a disaster. Will look into the red valves and hopefully it's not difficult to replace