What Is A Reverse Osmosis Pressure Tank and How It works?

If you own or are considering a reverse osmosis (RO) water filter , you’ve probably come across the term “pressure tank.”

While it might sound like a minor part of your filtration system, this small tank plays a huge role in ensuring that you always have a steady supply of pure, great-tasting water right at your faucet.

In this guide, we’ll break down what an RO pressure tank does, how it works, common issues, maintenance tips, and when to replace it.

By the end, you’ll know exactly how this unsung hero keeps your drinking water clean and flowing efficiently.

An RO pressure tank serves as a water storage tank designed to fit underneath your sink, and work in-line with your existing Reverse Osmosis system . This add-on acts as a collection tank for any resulting purified water produced by your RO unit.

Since the RO filtration process is slow, it can take several minutes to produce just a few ounces of water — the tank acts as a buffer to make sure filtered water is available instantly when you open the faucet.

Without a tank, the RO system would have to filter water on demand every time you turn on the tap, which would mean waiting quite a while for just one glass of water.

So, in short:

• The RO pressure tank stores filtered water.
• It provides consistent water pressure on the faucet.
• It ensures a steady flow, even during high demand.

In short, a pressure tank surrounds an internal inflatable air bag that makes up an RO pressure tank. As water enters into the bladder, the bladder is thereby squeezed to enable the inlet water to be subjected to pressure of the opposite direction. The pressure barrel is filled with water once the pressure equalizes to that of the inlet water pressure.

Inside the tank, there are two chambers separated by a rubber bladder or diaphragm:

1. The upper chamber holds purified water.

2. The lower chamber contains compressed air.

As your RO system filters water, it fills the tank and pushes the bladder upward, compressing the air below. When you open your faucet, the compressed air pushes the water out through the line, giving you strong, consistent flow.

This design is simple but highly efficient. The air pressure does all the heavy lifting, no electricity needed.

It is completely necessary to understand that regardless of the size of your pressure tank, it will have zero influence on the overall water production efficiency of your RO system.

Because an RO system which lacks a storage pressure tank will need to run continuously throughout the day, it isn’t recommended that you connect it directly to a fridge or ice maker.

To combat this issue, the pressure tank was created to enable users to store filtered water for various appliances, including ice makers.

One of the common problems you have probably faced with your RO system is the need to wat for water to be produced. An RO membrane takes more time to filter water due to the small size of the pores.

This is necessary for the removal of tiny, seemingly insignificant contaminants – something an RO system is known for.

A storage tank eliminates this issue, by storing filtered water for instant use at any time of the day.

Reverse Osmosis system is completely reliant upon electricity to operate, it could leave you “stranded” in dire times.

This means, in the event of a power outage , you will be unable to utilize your RO unit to produce filtered water for consumption. However, by installing a pressure tank, you are poised to store water for emergency use.

When reverse osmosis is connected to appliances in long-distance, there would be pulse problems.

The pressure tank perfectly resolves this problem by improving water flow with no decay. The suitable distance of PMT between tank and RO system is up to 16 feet.

The Waterdrop PMT Pressure Tank is an accessory designed primarily to optimize the performance of tankless Reverse Osmosis systems, especially when they are connected to auxiliary appliances like a refrigerator or an ice maker.

• Creative solution for tankless RO system: Faster water output in long distance connection. With this tank, you never worry about frequent reboot caused by unstable water pressure
• DIY installation: The manual provides simple instructions on how to install this water pressure tank. You get a ¼” quick-connect design out-of-the-box.
• Best-in-class quality: This pressure tank has undergone several tests, such as burst, pulse, static pressure, fall off, and tightness tests. The tank is super-durable and will not even leak in the event of high pressure.
• Premium and safe materials: Only high-quality food-grade materials make up each component of this product. They are 100% safe and sustainable.

If you need more water, you can upgrade to a high-flow RO system like Waterdrop X12 or Waterdrop X16 , which delivers 1200-1600 gallons per day.

They're designed for family efficiency, they deliver a rapid flow of healthy water, ensuring no more waiting, just instant, pure hydration for you at home.

Check it once a year or whenever you notice reduced water flow. The ideal air pressure for an empty tank is around 7–8 psi.

Yes, it’s relatively simple. Here’s how:

• Turn off the water supply and release any pressure by opening the faucet.
• Disconnect the tubing from the old tank.
• Install the new tank and connect the tubing.
• Turn the water back on and check for leaks.

Here are a few telltale signs that your tank might need replacement:

• The water trickles instead of flowing smoothly.
• You hear gurgling sounds when the tank fills.
• The tank feels full but no water comes out.
• You can’t maintain proper air pressure (it keeps dropping).
• You notice bad taste or odor in the water (stagnation).

Common indicators include frequent on/off cycling, noticeable water hammer, reduced water pressure, and signs of leakage or a waterlogged tank. A professional can test the bladder, check air charge, and verify the pressure switch to confirm a failure.

A pressure tank itself does not filter drinking water. It sits upstream in the system to regulate pressure. For better tasting and cleaner water, pair the system with appropriate filtration, like the whole house water filtration system . Make it suits your water quality goals without compromising tank performance.

Whether you choose a traditional RO system with a pressure tank or a modern tankless design . The goal is the same, to enjoy a steady supply of clean, safe, and great-tasting water.

A pressure tank offers reliability and consistency, especially for households that use moderate amounts of water throughout the day.

On the other hand, tankless systems provide fresher water on demand, faster flow, and more under-sink space, a perfect fit for modern kitchens.

No matter which system you choose, investing in a quality reverse osmosis solution ensures your family always has access to pure, refreshing water — every time you turn on the tap.