Are you on city or a well system? Most well systems do not have the pressure to run a unit at max efficiency. I have a well system with a 30/50 pressure switch on the pump. I put a ro pump on my new unit and it really produces. I think there is a optimum pressure to run at. If the pressure is too low then more waste water is produced since it can't force it through the membrane. I think the more pressure the more effective the unit becomes. I have a 100gpd unit 6 stage with UV, a pressure tank, sink faucet (for drinking), Dual in line TDS meter, auto shut off switch and a booster pump. There are threads here talking bout ro/di's and efficiency also.