Pressure vessel for Reverse Osmosis (RO) membrane is made of fiberglass reinforced (FRP), specifically manufactured to contain the membranes and withstand the high pressures required by RO system to run. The manufacturing process is computer controlled with each strand of glass fiber placed at a specific location and orientation to achieve optimum strength. The glass fiber and resin mixture is wound around a precision-machined mandrill, which accounts for the perfectly circular, defect free interior of today’s RO vessels. The vessels are often painted white to reduce light transmission through the vessel to minimize growth of algae and other biological concerns.

RO vessels are available in a range of pressure ratings depending on the membranes being used and the type of water being treated. Sea water has high osmotic pressure (~400 psi), meaning that high operating pressures are required to overcome the osmotic pressures developed in the concentrate stream. Other common pressure ratings are 300, 450, 600 and 1,000 psi. Newly developed higher pressure ratings (up to 1,800 psi) are now available.