How to Purge a Reverse Osmosis System

This page may contain affiliate links. If you buy a product or service through such a link we earn a commission at no extra cost to you. Learn more.

Installing a new reverse osmosis system or sanitizing one, or replacing an RO membrane requires a purging process. This step ensures the optimal functioning of the filtration process.

But there is a lot of conflicting information around how to purge an RO system and how long for.

Today, we are going to clear all that up for you!

Key Takeaways

Here is how to purge a reverse osmosis system:

  1. Turn on your water supply to the RO system.
  2. Open the RO faucet and let the water flow through the system for the recommended time frame.
  3. Once complete, close the RO faucet.
  4. Allow the system to fill the storage tank.

How to Purge a Reverse Osmosis System

So, how do you purge a reverse osmosis system?

Purging your reverse osmosis system essentially just means running water through it with the faucet on for an extended period of time. The water flow will be slow, and you shouldn’t consume any water from the system during this period. After a duration of time, close the osmosis faucet and give the unit a few hours to fill the storage tank. The duration can vary depending on your tank’s size. Once the tank is full, your system is ready for use.

The following is a step-by-step guide for how to purge your RO system:

  1. Turn on your water supply to the reverse osmosis system.
  2. Open the reverse osmosis faucet and let the water flow through the system for the recommended period of time.
  3. After this, close the RO faucet.
  4. Allow the unit to fill the storage tank.
  5. Your system is now ready for use.

If due to system sanitization there is still bleach smell after purging, continue to let the water run until the smell is gone. Do not consume any water that smells like bleach, as it can be harmful.

under sink reverse osmosis system

How Long to Purge a Reverse Osmosis System

Many sources suggest purging a reverse osmosis system for 24 hours. This time frame guarantees the removal of any installation debris, membrane preservative, bleach, and other particles and chemicals, maintaining the safety and cleanliness of the water.

However, a total 24-hour purging for an RO system could be excessive for certain scenarios. When initially setting up the system, following the manufacturer’s guidelines on how long to purge is a good idea. Usually, in cases of changing the RO membrane or sanitizing the system, the process can be simplified to filling and discarding between one and three tanks. This usually takes less than 24 hours, with a single tank taking roughly 2-4 hours to fill and discard, depending on the capacity of the water tank. Smaller tanks may require less time.

Another practical way to determine a suitable purging duration if you have cleaned your RO system with bleach is the absence of bleach odor. Only stop purging when you no longer detect the smell of bleach.

How Often to Purge a Reverse Osmosis System

There are three specific circumstances where purging an RO system is recommended: immediately following the installation of a new RO system, after the replacement of an RO membrane, and after sanitizing an RO system using bleach or another cleaning agent.

An RO system is designed with various stages, each consisting of different types of filters. The initial stage involves a pre-filter that efficiently removes larger contaminants like dirt, sand, and sediment from the water. This pre-filter requires replacement every six to twelve months, aligning with the recommended purging schedule.

The subsequent stage incorporates a carbon filter for eliminating odors, chlorine, and other chemicals. The longevity of the RO membrane greatly depends on this carbon filter, which also needs replacement after six to twelve months.

The third stage of the process, the actual reverse osmosis phase, involves water passing through a membrane under high pressure. This allows for the separation of pure water from contaminants. While the other filters require frequent replacements, an RO membrane can function effectively for over two years if conditions are optimal.

The final stage of the process involves another carbon filter that eradicates any remaining odor or taste in the water. Similar to the earlier carbon filter, this one also needs replacement about every 12 months, coinciding with the purging schedule.

Why Purge a Reverse Osmosis System?

Purging has three primary purposes in maintaining a reverse osmosis system: it removes chemicals post-sanitization, eliminates debris after installation, and primes an RO membrane (and the other filter elements).

blue reverse osmosis membrane

Freshly Installed RO System

To flush a new reverse osmosis system, open the RO faucet and let the water slowly drip out for the recommended duration. This purges manufacturing debris and primes the filter elements, removing carbon dust and preservatives. Don’t drink the water during this process. Some manufacturers recommend a 24-hour purge, while others suggest filling and discarding the tank 1 to 3 times. This method flushes the tank, removing debris and eliminating unpleasant tastes or odors.

New RO Membrane

Once an RO membrane is replaced, a subsequent step of purging is necessary. This process eliminates any preservatives that manufacturers may have applied to the RO membranes.

After Sanitization

Sanitizing an RO system is recommended every 6 to 12 months to eliminate microbial contamination. After sanitizing, thoroughly purge the system to ensure no cleaning chemicals are ingested. Note that opening the RO faucet before the tank fills may bypass the tank. If the tank is connected during sanitization, fill and flush it to remove residual chemicals. The system is sufficiently purged when there is no chemical taste or odor in the water.

If you have any questions about purging a reverse osmosis system please don’t hesitate to leave a comment below!

About the Author Gene Fitzgerald

Gene Fitzgerald is one of the founders of BOS and currently head of content creation. She has 8+ years of experience as a water treatment specialist under her belt making her our senior scientist. Outside of BOS, Gene loves reading books on philosophy & social issues, making music, and hiking.
Learn more about .


Information provided on BOS is for educational purposes only. The products and services we review may not be right for your individual circumstances.
We adhere to strict editorial guidelines. Rest assured, the opinions expressed have not been provided, reviewed, or otherwise endorsed by our partners – they are unbiased, independent, and the author’s alone. Our licensed experts fact-check all content for accuracy. It is accurate as of the date posted and to the best of our knowledge.

Leave a Comment: