Reverse osmosis storage tank (Best pressurized)

Reverse osmosis system treats water slowly, so you need a storage tank that will collect purified water that is gradually treated. Without the tank, you can end up waiting for long to fill a glass of water or a pot when you open the kitchen faucet. The tank collects water so you can have immediate access to treated water.

The reverse osmosis storage tank is designed to be stored under the sink in line with your under sink reverse osmosis system.

The storage tank is where filtered water is stored waiting to be transported to its point of use. Storage tank comes in different sizes and this depends on the amount of water your family consumes

How does a reverse osmosis tank work?

Most people ask themselves as they physically look at the tank the way out is at the top not at the bottom as many tank how does the tank deliver water right on your faucet or point of use.

Reverse osmosis tanks use air pressure to deliver water to the kitchen faucet. The air pressure help deliver water without the use of a booster pump.

Inside the tank, there is an air pressure chamber and water pressure chamber. The air pressure chamber is at the bottom while the water chamber at the top.

As purified water gets into the storage tank, the weight of the water will compress the air chamber. The more the air chamber compresses it will continue to increase the pressure. When you open the faucet the pressure will force water out of the tank to the faucet.

If the tank did not have pressure even if is filled with water it will not be capable of delivering water to the faucet unless you are using the delivery/demand pump.

So reverse osmosis tanks are special they are Pre-Pressurized to provide water efficiently to the faucet.

In case your tank that came to the RO system is not providing water and you have done troubleshooting you need to replace the tank by buying a new one.

That’s why we have provided a review of reverse osmosis storage tank replacement

Express Water RO132-TNK 4.0 gal Reverse Osmosis RO Water Storage Tank by TANKRO

Reverse osmosis storage tank

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The tank pre-charge about 5-7 psi

Express tank is manufactured using finest FDA best material such as stainless steel, polypropylene, and butyl rubber.

The tank is 4 gallon and holds 3.2 gallons of water.

iSpring T32M 3.2 Gallon Pressurized Storage Tank for Reverse Osmosis (RO) Systems

ro storage tank

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The tank size is 3.2 gallons and designed for reverse osmosis application

To guarantee safety, the tank is constructed using stainless steel, food grade material, and FDA compliant material. It is NSF approved.

6.0 Gallon (5.5 Draw-down) Reverse Osmosis RO Water Storage Tank by PA-E

RO storage tank

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To ensure you are consuming standard water the tank is manufactured using FDA compliant material and food grade material. It is NSF approved

The tank size is 6 gallons and 5.5 drawn down

Purenex PRO 3.2 Reverse Osmosis Water Storage Pressure Tank

Reverse osmosis storage tank

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To make sure the tank is safe for human use it is certified by NSF and CE. It is also made of FDA approved bladder, food grade, no rubber smell, no plastic smell, stainless steel connection on top

 The tank is 4 gallons and holds 3.2 gallons of water

It is pre-charge with the 5-7Psi pressure of air.

What to consider when buying a reverse osmosis storage tank


Capacity is the amount of water the tank is capable of holding.

The storage tank comes in different sizes measured in a gallon. The size you require depends on your household usage. If you have a large family you need a bigger tank for you to get enough water and vice versa.

In addition to the capacity of the storage tank, you should know the tank does not hold the amount of water the manufacturer says. If your tank is labeled 4.5 gallons remember that tank has two chambers inside one for the air and the other for water. You will find that the tank will hold 3 gallons of water and the other part will be occupied by air. 

The 4.5 gallons is the total amount of water the tank will hold without air but if it is pre-pressurized it will hold less. 

Can I increase the tank capacity with a second tank?

You can find the case where you bought a RO system with small tank storage capacities in such incidences you will receive less water required for your household. 
You can increase the tank capacity by adding the second tank.
Also, there are incidences you will find the tank is getting less water than its capacity you can increase the capacity by adding booster tank.
This happens if the water supply has low pressure, more water will go to waste and less water will go through reverse osmosis membrane leading to less water going to the storage tank.
By increasing incoming water pressure the tank will accumulate treated water faster.

How do I add pressure back to the tank if lost?

If the storage tank has lost its pressure there is a valve at the tank mostly at the bottom part you can use to add pressure.
You can use a bicycle pump to add pressure to the tank.

How long does the storage tank last?

Most storage tank last 10-15 years

How do you know it’s time to replace the storage tank?

Counting 10 years or so is not easy for you to know it’s time to replace the storage tank but some signs can tell you it’s time to replace the tank. Such as 
If you add pressure to the tank as described above and purified water fails to come out of the tank to faucet it’s time to replace the tank.
If the water comes out at the air valve this means the bladder that divides air and water chamber is damaged. There is no way to repair the bladder that means the tank requires to be replaced.


How to add a pressure tank using a bicycle pump

Open the cap covering the valve. Use a bicycle pump to ad pressure. The standard pressure required for the majority of the tank is 7PSI. You can use a pressure gauge to monitor pressure not to over/under pressure. Add pressure until water will start coming out of the tank.

If you add more pressure that required that is above 7psi you will reduce the amount of water the tank will hold.

Reverse osmosis tank pressure 

The standard pressure required for the majority of the tank is 7PSI

Reverse osmosis tank not filling up

There are incidences you will find the tank is not filling up. 

If the tank is not filling up it is mostly caused by feed water pressure (check the water pressure gauge to measure your incoming water pressure). If the feed water pressure is low, water is not capable of going through the RO membrane leading to more water wastage, therefore the system produces less purified water to go to the storage tank.

If less water is purified you will end up having your storage tank not filled with water.

To solve the problem increase your incoming water pressure using a booster pump 

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