What Is A Reverse Osmosis Tank? – Useful Information For RO’s Users

The RO has become one of the top choices among other selections for filtering water systems. Nonetheless, some people still have doubts about the tank design and believe it’s an unnecessary installation.

So, what is a reverse osmosis tank and how does it work? Is it the same with other storage tanks? Explore the detailed answers in our article below.

RO Tank
RO Tank

What Is A Reverse Osmosis Tank And How Does It Work?

Let’s dive in and see how this wonderful tank works.

What Is A Reverse Osmosis Tank?

Before getting insight into the reverse osmosis (RO) tank, we first need to learn the meaning of the RO system. Reverse osmosis is a water filtration technique operating by reversing the natural osmosis principle. This process utilizes pressure to push water from higher to lower salt concentration through a permeable membrane.

So, where does water flow to after this filtration?

It is where a reverse osmosis tank comes in. The RO tank is a hydropneumatic tank that stores purified water after filtration. This pressure tank includes two basic partitions: a water reservoir and an air chamber, divided by a butyl bladder. Normally, it is designed under the sink and next to the filtration part of the RO system to ensure the aesthetic aspect and most effective operation.

Though the filtering process happens slowly, the presence of the storage reservoir at the end of RO filtration allows it to accumulate and provide water by the inner pressure. Thereby, you can have a glass of clean water as soon as turning a faucet on without waiting. 

Reverse Osmosis Principle
Reverse Osmosis Principle

How Does The Process Of RO Tank Work?

Now, let’s explore how it works in the whole RO system.

In simple terms, the RO tank works as a connector between RO units and the faucet. After filtration, water flows into the RO tank and keeps on accumulating. The tank then stores purified water and gets ready to supply when needed.

Yet, how does this tank provide water without any pumping tools? 

The secret lies in the air chamber within the RO tank. When a reservoir is full of water, its weight will produce pressure on the air chamber. The compressed air will create a propulsive force to supply water without the pump supports as soon as you run the faucet.

What’s more, this tank operates simultaneously with the sensor pressure valve to automatically open and close. When the tank pressure reaches the standard rate (⅔ of the total line pressure), this automatic shutoff valve will interrupt the amount of water flowing into the tank as well as stop all the water production.

As a result, the setting of the shutoff valve in each tank is different depending on the regional pressure level of the water source. If the water supply pressure is below 50 psi, the RO may have difficulty continuously providing water.

The Importance Of RO tank

If called “tank” – of course, the main role of RO tank is to store water. Don’t be surprised, it’s more than that!

Thanks to the hydropneumatic function, this storage tank speeds up the water supply. Suppose the RO system does not contain a hydropneumatic tank; what then? – Perhaps, you have to wait for even more than 4 minutes for only one glass of water as the treated water is still in a filter process.

According to RO tank suppliers,  the automatic shutoff valve of the tank can help save thousands of gallons of water each year. Without it, the filtration system will continuously pump the water down to the drain, not to the full-water tank. 

How To Sanitize The RO Tank

Regardless of any filter system, it would be best to sanitize the RO tank at least once a year to remove the built-up and ensure a germ-free environment for RO water. Below are three steps to clean the RO tank you can refer to.

Step 1: Remove The Storage Tank Out Of RO System

Turn off the valves linking to the main water supply pipe. Generally, these shutoff valves are found under the sink.

RO tank installed position
RO tank installed position

Next, locate the point where the incoming water line connects to the RO water tank. This point often comes covered by a plastic nut. So, it would be best if you had a plie to loosen it.

It would be best to place some old rags under the tank and surrounding areas. Or else, the water inside the incoming waterline will spill out the floor when loosening the nut.

Step 2: Clean It Up 

Prepare some cleaning solutions, either handmade or specialized sanitizers, and pour into the tank through the opening you’ve just disengaged the incoming waterline. 

Wait for a few minutes, then use a bottle brush to scrub the tank insides and clear the contaminants out. For the cover, use a sponge with dishwasher soap to clean the outside surface. 

Step 3: Dry Up And Reconnect

Wipe the surface with a dry cloth, use a plie to tighten the nut, and turn the shut-off valve on. Now check if the RO system works by opening the faucet and observing whether the water flows out. 

It’s worth noting that the first amount of water probably contains some drops of cleaning solution. Hence, make sure you only use it for household purposes after at least the first 5 gallons.


Does Reverse Osmosis Remove Microplastics?

Yes. Many studies have indicated that the RO system can get rid of even microplastics as small as 0.001 microns in size, which can cause fatal diseases such as weakened immune systems, cancer, and childlessness. Consequently, you can rest assured while using purified water produced from this system.

How Large Is The Tank Capacity Of A Reverse Osmosis Tank?

RO tank suppliers currently offer a variety of tank sizes. The smallest capacity tank can hold up to 2 gallons, while the largest endures 14 gallons. It is important to note that the actual tank capacity of the RO system differs from the volume of the standard tank index.

Specifically, it depends on the inside structure, including spaces for the air chamber and bladder. Hence, if the catalog shows the storage tank is 4.5, the actual holding is around 3 gallons of water. The amount of water to fulfill the tank also relies on three factors:

  • The air pressure
  • The water pressure
  • The shutoff pressure
4.5 gallons inside capacity
4.5 gallons inside capacity

If the present volume is not enough, you can insert one more tank to increase the tank capacity. Alternatively, adding a booster pump for the pressure valve can also speed up the water filter process.

What Should We Do To Repressurize The Reverse Osmosis Tank?

Your RO might have a noisy drain or low/slow water flow due to less tank pressure after long-time usage. This status occurs because of the infinite air releases and the ineffective bladder work.

When it happens, you need to check the tank’s weight, which must be about 20 pounds. If less, let’s re-pressure by the following steps:

  • Step 1: Close the shutoff valve and disassemble the tank from the RO system. Make sure the tank is empty, and the water can not penetrate inside it.
  • Step 2: Using the bicycle pump to gain the pressure coming up to approximately 7 psi. Please note that you have to measure carefully to avoid getting under or over the standard pressure.  
  • Step 3: Reinstall the tank and open the valve back.

After finishing all steps, continue to track the tank operation. If it fails, it means you should replace the bladder or even the entire tank.

Is Reverse Osmosis Water Good For You?

Yes! The clean water from the RO system is beneficial to your health. RO filtration can take out more contaminants than other normal filters, including bacteria, sulfates, fluoride, chloride, etc.

That being said, some people wonder whether it removes essential minerals in the water. Our answer is: it does remove the minerals, but they are not as nutrient as those provided by food. According to the studies, using water that lacks these minerals doesn’t affect your health. So, there is no need to worry that the RO system will remove your required minerals.

There are also opinions that the exposure between the water and external material impacts the quality of water. The truth is that water doesn’t expose directly to these metals. It only exposes the butyl bladder surface, which is unharmful to your health.

Treated Water from RO process


Now that you got the detailed answer to the questions – what is a reverse osmosis tank? How At the same time, you can also understand why the tank installation in the RO system is necessary – to store water and avoid its wastage. Though it does not contribute to creating pure water, we can not underestimate its main role in the whole RO process.

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