Big Brand Water Filter offers many reverse osmosis membranes for different water conditions :

Tap Water reverse osmosis membranes Tap Water reverse osmosis membranes are for water with a TDS below 2,000 ppm.
Within the tap water membranes there are standard and low energy membranes. Newer membrane technology allows high rejection at lower pressures. Sometimes with cold water we run low energy membranes at 180-200 psi to compensate for the loss of reverse osmosis water production due to cold water temperatures.

Brackish water reverse osmosis membranes are similar to the tap water RO membranes and usually you can use brackish water membranes for tap water reverse osmosis applications. Brackish water membranes have a fiberglass outer wrap instead of tape to be able to withstand higher operating pressures. Brackish water membranes also often have a bigger spacer between each membrane leaf to allow for more cross flow along the membrane surface.

Sea Water Reverse Osmosis membranes cannot be used on tap or brackish water applications. Sea water RO membranes operate at much higher pressures, anywhere from 650-1100 psi in order to overcome the osmotic pressure of sea water. A rule of thumb is each 100 ppm of TDS (total dissolved mineral content) resuced the pressure across the membrane by 1 psi. Seawater averages about 35,000 ppm so it takes more than 350 psi just to overcome backpressure caused by the salinity.