Why You Should Soak And Flush Water Filters


Soaking a water filter before first use is necessary to optimize the filtration process. 58% of individuals use some form of home filtration system. For many, it may seem silly to soak a water filter as it’s going in water anyway, but knowing why soaking is important, and how to do it properly filter can go a long way in making your water filter work efficiently.

A water filter must be soaked to make filtration quicker and more efficient, as soaking increases the surface area of the adsorbent (filtering mechanism). This allows water to be filtered at a uniform rate throughout the filter cartridge.

While it is a general rule that you must soak your water filter before using it for the first time, instructions may vary from brand to brand (more information below).

In this article, I’ll explain 5 reasons why you should soak a water filter, how long you should soak them, and go through a step by step process on how to soak different water filters properly.

First, here are the 5 main reasons why you have to soak a water filter.

5 Reasons Why You Have to Soak a Water Filter

1. Aiding Chromatographic Filtration

Most water filters operate on the principle of liquid chromatography. This technique is useful in separating different components of water, like heavy metals, hard water, and other contaminants.

Here, tap water flows through the filtration column that contains a chromatographic filtration mechanism (usually activated carbon and/or ion exchange resins).

Pre-soaking your water filter increases the amount of area it has in contact with the water. Liquid chromatography does not work as efficiently if there are any trapped air bubbles or particles in the water filter. Soaking a water filter will make your water filter more efficient.

Activated carbon removes contaminants through three main processes:

  • Adsorption
  • Absorption
  • Chemical reactions

Adsorption effectively removes contaminants from the water by causing them to stick (adhere) to the carbon surface. This “stickiness” is caused by an electrostatic attraction – kind of like a magnet – that tightly holds the contaminants in place.

Some filters may use carbon in an impregnated cellulose mesh. The same principle (adsorption) is used here to remove contaminants. 

Absorption is different from adsorption. Absorption removes contaminants like a sponge – contaminants get “trapped” in the carbon pore spaces, but do not get stuck to the carbon surface like adsorption. Absorption is the process of mechanical water filtration.

Chemical reactions occur both in activated carbon and ion exchange water filters. Some water filters may use both processes in the one filter.

Activated carbon chemically alters some contaminants into products that are less harmful or simply may make the water taste better. A good example is chlorine. Activated carbon chemically alters chlorine and turns it into chlorine ions (this means it now holds a negative charge). Luckily you can’t taste or smell chlorine ions, unlike chlorine, which makes the water taste better.

Ion exchange resins removes heavy metals through electric charge transfer. Other ion exchange resins, like the ones used in coffee machines, work by exchanging limescale forming minerals – namely calcium and magnesium – with other minerals such as sodium or potassium.

2. Increasing Surface Area of Adsorbent

When you soak a water filter, water enters and completely wets the chromatography column.

When all of the tiny channels in the water filter are completely soaked, the contaminants have a greater chance of being adsorbed, absorbed or chemically altered within the filter. This allows only clean filtered water to run through.

If you don’t soak your filter beforehand, the channels within the filter are not fully formed, and the whole surface area of the activated carbon column is not used.

Even a small area of carbon makes a huge difference – a gram of carbon has a surface area of more than three thousand square meters (or thirty-two thousand square feet), because of its high microporosity.

Therefore, not utilizing all the carbon available in the filter would prove detrimental to the filtration process.

3. Flushing Out Carbon Dust

Activated carbon is a fine black powder that contains micropores. The water filter’s chromatography column is packed with activated carbon, usually with a coconut mesh. Since water filters use activated carbon, there is often carbon dust that gets dislodged during initial use.

Soaking and flushing your water filter helps remove this carbon dust. You will notice that when you flush your filter, these black flecks flow out with the water. Discard this water and continue using your filter. 

Refrigerator water filters may need to be flushed a few times. Run one or two gallons of water through the filter before drinking. If you still notice cloudy water or black flecks coming from the water dispenser or in your ice tray then it probably needs flushing again. Remember to discard the first one or two trays of ice after a water filter change.

4. Removing Clogs in the Pores

While the filters are securely sealed, there may be packing material like Styrofoam flakes or plastics lodged in the device. Soaking and flushing your water filter helps remove any clogs that may be blocking the fine pores of the filter.

Most water filters also have a mesh or screen at the top before the water can reach the filter itself. This mesh may also be clogged. Soaking and flushing the filter removes any small particles and frees up the pores for optimal filtration.

5. Quicker Filtration

As soaking your water filter helps increase the filtration capacity and removes any clogs, it makes filtration faster.

As time passes, however, filters lose their efficiency as the contaminants build up inside.

If you don’t pre-soak your water filter, you may be using less of the available spaces on the filter, which means the filters lifespan by get prematurely shortened. This can result in slower filtration speeds and means you may have to replace the filter sooner than necessary.

Keep in mind that you must soak every replacement filter before first use.

How Long Should I Soak a Water Filter

Water filters should be soaked for 10-15 minutes before first use. After soaking, flush the water filter 2-3 times under running water to remove any lose particles including carbon dust.

While this may vary between brands, a minimum pre-soak of 10-15 minutes is a good guide for all water filters.

You can’t over soak your water filter but it can be under soaked.

If you accidentally left your water filter soaking for longer than 15 minutes it won’t do it any harm, but it will start to adsorb some contaminants from the water.

It’s important to follow the recommended soak time for your filter but make sure you don’t under soak it. Otherwise the filter may not work as efficiently, it can run slower, and it can become used up sooner.

Keep reading to find soaking times for common water filter brands. 

How to Soak a Water Filter

  1. Wash your hands with water and soap for at least 20 seconds.
  2. Remove the filter from its sealed bag.
  3. Place the filter upright in a jar of cold water for 10-15 minutes.
    • Do NOT use boiling hot water to soak your filter. This may damage the filtration mechanism and ruin your filter. You may use water at room temperature but use cold water if available.
  4. Then, hold the filter upright as you flush it under cold tap water for a few seconds.
  5. Keep in mind that your water filter is to be used to purify water that comes out of your tap only, as it cannot remove any microorganisms. Therefore, do not use untreated well water, spring water, or any water that comes from an underground aquifer to soak your filter. This may contaminate the filter with bacteria and other microorganisms.
  6. After soaking and flushing your filter, attach the filter to your device following the manufacturer’s instructions. Usually, there is a twist-and-lock mechanism involved. You will be able to hear a snap as the filter locks securely into position.
  7. Do not forget to also wash your filter device (e.g. pitcher, faucet filter mount, coffee machine water tank etc.) with soap and warm water while soaking your filter. Dry off your filter device before inserting the filter. Discard the first 3 volumes of water to remove any remaining carbon dust and soapy residue.

Do All Filter Brands Need to be Soaked?

Water filters that rely on gravity to filter the water, such as water pitchers and coffee machine filters, will need soaking first. Water filters that work by having water forced through them, such as reverse osmosis, cation exchange, refrigerator filters, and faucet filters, do not usually need to be soaked before use. In general, all filters should flushed.

However, it does depend on the brand of the filter and the type of filter.

S.No. BrandShould the Filter Be Pre-Soaked?Additional Instructions
1Brita Filter PitcherYesSoak for 15 minutes
2PUR Pitcher DispenserYesSoak for 15 minutes
33M Foodservice Water FiltrationNoFlush filter 2-3 times
4Epic Pure Water FilterYesFilter can be soaked within the pitcher itself
5Aquaboon RO FilterNoFlush filter 2-3 times
6ISpring RO FilterNoFlush filter 2-3 times
7Paper Coffee filtersYesSoak for 5 seconds
8ZeroWater FilterNoFlush filter 2-3 times

When it comes to pre-soaking paper coffee filters, it is recommended to gently pour hot water over it before use. This helps to unclog the pores and remove any papery taste from the coffee. It is not recommended to use a paper filter more than once.

The Bottom Line

Caring for your water filter, be it a pitcher or an RO filter, is necessary for efficient performance. Soaking your filter before use is a simple way to ensure you get the best out of your device. Make sure to read the instructions from your filter’s brand so you can get tailored guideless for your model.

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