not sure what brand you have, but if its a culligan, TAKE IT BACK. everything culligan makes is way over priced JUNK
They sold me a filter,water softener, and under sink RO unit $3500 total ripoff price
the RO unit never made enough water to drink,always wasted water to drain 24/7 and tasted funny to boot
(RANT OFF)

the best units are Merlins@$450-$500, as they waste the least amount of water only 3 gal waste for every gal made. and have a shutoff float valve that is supposed to stop the incoming water, so its not wasting h2o because the res. is full. does your unit have a booster pump?, if you don't have at least 50psi of water then you might need a booster.

but honestly unless your water is like mine ,sulfur and hard iron 350ppm,you probably don't need the headache of RO