Anti-telescoping device (ATD): An anti-telescoping device or ATD is a plastic device located on the ends of a reverse osmosis membrane element in order to prevent the membrane from telescoping under pressure.
Concentrate or Brine: Concentrate or Brine is the water that did not pass through the semipermeable membrane and is rejected with a high concentration of contaminants.
Dry Membrane: A dry membrane has not been tested for quality assurance and has not touched water therefore is dry.
Envelope: One sheet of permeate water carrier sealed on three sides within a folded sheet of membrane.
Feed water: The original water supply that enters the RO system before any of the contaminants are removed.
Membrane casting: Casting is the technique used to produce membranes.
Membrane Element: All membranes are cast inside of what is called the membrane element.
Permeate: Permeate is the product water that passed through the semipermeable membrane and is now pure water free of most contaminants.
PPM: Total dissolved solids which are present in the water supply are measured in parts per million (ppm) which is a common unit of measurement for concentration.
psi: Pound per Square Inch and is a common unit of measurement for pressure.
Reverse Osmosis: Reverse Osmosis is a water treatment technique which removes 99.99% of water contaminants using pressure to force water through a semipermeable membrane filtering out contaminants.
Salt Flux/Salt Passage: Salt Flux or Salt Passage refers to the amount of contaminants that pass through the membrane (less than 1% with RO).
TDS: TDS stands for the Total Dissolved Solids present in the water supply.
Water Flux/Water Passage: Water Flux refers to the flow of water through a semipermeable membrane (net driving pressure and temperate affects water flux). The higher the Flux the higher the quantity of permeate produced.
Wet membrane: A wet membrane element was tested by the manufacturer for quality assurance by testing its performance under ideal operating conditions.
Please add any terms you don’t see here in the comments below.