The Role of the Storage Tank in a Reverse Osmosis Purification System

The storage tank is an essential component of a reverse osmosis system, playing a crucial role in ensuring efficient operation and quality drinking water. Water purification through reverse osmosis is a slow process, and this is the main reason we need to store water and use it when needed. It is true that modern reverse osmosis systems have a high filtration capacity and provide a direct flow, without the need for a storage tank. However, it takes 4-5 seconds for the flow of a direct-flow reverse osmosis system to reach its maximum, which is why we also recommend a very small tank (0.5 litres) for these systems, to provide you with instant water.

Main functions of storage tanks:

• Water storage: The tank stores water purified by reverse osmosis. This allows a constant flow of purified water, even when the system is not active. The tank provides pure water even when the supply is turned off.
• Optimal pressure: The tank maintains a constant pressure of the purified water. Adequate pressure is essential for the proper functioning of appliances and devices that use purified water.
• Comfortable flow rate: The tank provides purified water at an optimal flow rate for consumption. The flow rate is approximately 2 litres per minute.

How storage 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 level, filtration starts automatically. Regardless of whether the filtration system has a pressure pump or not, 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 contains an internal rubber membrane that separates the water from the compressed air. At the bottom, there is pressurised air 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. Food-grade plastic (BPA Free) tanks are lighter and cheaper than stainless steel tanks. Plastic tanks are used mainly for residential systems and have a storage capacity of between 1 and 15 litres. Stainless steel tanks are durable and corrosion-resistant, but are more expensive and heavier. These are used in commercial and industrial applications and have storage capacities of over 30 litres. 

Available tank models:

• Mini tank for direct flow reverse osmosis, for instant flow, total volume 1 litre, useful volume 0.5 litres
• Slim tank for residential reverse osmosis, total volume 7.5 litres (2 gallons), useful volume 3.8 litres (1 gallon)
• Standard tank for residential reverse osmosis, total volume 12 litres (3 gallons), useful volume 6.8 litres (1.8 gallons)
• Medium tank for commercial reverse osmosis, total volume 34 litres (9 gallons), useful volume 20 litres (5 gallons)
• Large tank for industrial reverse osmosis, total volume 76 litres (20 gallons), useful volume 44 litres (12 gallons)

Choosing the right storage tank depends on your specific needs. Factors to consider include:

• Size: Choose a tank large enough to store the amount of purified water you need.
• Material: Consider the advantages and disadvantages of stainless steel and plastic tanks.
• Budget: Stainless steel tanks are more expensive than plastic tanks.

Maintenance: It is important to regularly clean and maintain your storage tank to preserve the quality of the purified water. Follow the manufacturer's instructions for cleaning your storage tank. At FILTRO, we recommend sanitising the storage tank every time the reverse osmosis membrane is replaced. This sanitisation procedure is carried out using a special chlorine-based solution, which is introduced into the filtration system when all cartridges have been removed. Allow the solution to act for a few minutes, then rinse thoroughly multiple times.

The storage tank is an essential component of a reverse osmosis system, offering a range of important benefits, including constant water availability, constant pressure, regulated flow rate and improved water quality. Choosing the right storage tank and performing regular maintenance are essential to ensure you get the best results from your reverse osmosis system.