Storage tanks

How the tanks work: Water purified by reverse osmosis flows from the reverse osmosis membrane into the storage tank. A special 4-way valve stops and starts the water filtration depending on water consumption and the amount stored in the tank. When the water level drops below a certain point, filtration starts automatically. Whether or not the filtration system has a pressure pump, filtration will start and stop automatically when the tank is full. Water enters and exits the storage tank through a single hose. To operate in this way, the tank has a rubber membrane inside that separates the water from the compressed air. At the bottom there is air pressurized at 0.5-0.6 bar (when the tank is empty). This air pushes the water out of the tank when the filtered water tap is opened.

Types of storage tanks: There are two main types of storage tanks used in reverse osmosis systems. Made of food-grade plastic (BPA Free), which are lighter and cheaper than stainless steel tanks. Plastic tanks are used especially for domestic systems and have a storage capacity between 1 and 15 liters. Stainless steel tanks are durable and corrosion-resistant, but they are more expensive and heavier. These are used in commercial and industrial applications. They have storage capacities of over 30 liters. 

Read more in the article The role of the storage tank in a reverse osmosis purification system.