no doubt.. i couldnt believe how much waste water there was with an RO unit.. luckily water is included with rent at the moment :D

The waste water will go way down if you get a booster pump!

26 is definitely low and thats your problem.

I have dual 100gpd membranes (so 200gpd) and I get about 100-150gpd out of them with a booster pump, but im on a well with SUPER cold water, with just the pressure tank supplying the R/O unit, I was getting like a 7:1 waste/product ratio, but now with booster its more like 2:1 waste/product.

Many homes have a Pressure Reducing Valve in their plumbing. Standard setting is around 60 psi. Should be adjustable to bring up the pressure, but since you're renting, I wouldn't mess with it, if you find one. With pressure at 25 psi sounds like you're on a well or something.