How to Fix this Water System?
Zane; I gave a suggestion in your duplicate ask, however the picture is now worth a thousand words , "as the saying goes". I can't see how having that large tank mounted somewhere in the house will be of any value since you can not elevate it high enough to produce any decent pressure. For each foot of height of the water level above the point of use you will get .433 pounds of delivery pressure. so, to get even 20 pounds water pressure to take a shower, the top of the water level would have to be about 46.5 feet above the shower head. (1 LB = 2.33 feet or 20 LB = 46.5 feet). If your picture is how the system was installed there are a few things you could do: 1)"Fire" that plumber and hire one that knows how to plumb a booster system.  2)Replace the red pressure tank with a very large bladder tank. and get rid of that large tank that is somewhere in the house. 3) Make the big tank just a storage tank with a double swing check mounted on the top of the tank. (A good plumber will know how to do this) and move it to between the house water supply piping and the booster pump. 3) convert that large tank to a bladder tank similar to the red tank or just use suggestion 2, and get rid of that tank.  My 2 cents