I upgraded my 75gpd brs rodi to the 150gpd. Being unsure how it would save water even though it runs the waist line though the second ro membrane I timed filling a one gallon jug and measured the waist water before I installed the second membrane. It was a few years ago so I do not remember the exact timing but before I filled one gallon of rodi and 4 gallons of waist in say 45 minutes. Once I installed the additional membrane I filled one gallon of rodi and 4 gallons of waist in about 20 minutes. I never actually saved water, or reduced waist as brs claims. It was the same ratio, just twice as fast.