All RO membranes output is subject to three things, your water quality, water pressure and water temperature. The RO membrane is rated at 77degress and 50 PSI For every pound of pressure lower than 50(psi) subtract 2% of the output. Example. using 40psi water pressure subtract 20% of the rated output. Temperature subtract 1.4 % per degree lower than 77 F. Water is as dense as it gets at forty degrees . R.O. membrane systems operated with 40 degrees F. water will produce one half as much water , as they would at 77 F.