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How Does the Water Filter in Your Fridge Filter Out Harmful Substances from Tap Water?

by Dearfilter - Updated 2022-12-23 15:46:48

Ever wondered how that water filter inside your fridge works? I did, and after some minor research I found out that fridge filters use chemical absorption to remove/reduce contaminants from tap water.

A lot of people believe that water filters are some sort of intricate machine like a microwave which uses laser waves to eliminate things like bacteria, but that’s just not the case.

Ancient Romans had these aqueducts (kind of pipes) to purify and distribute clean water to the city. And these pipes were made from nothing but sand, gravel and charcoal!

In 1996, KX Industries used the same concept to invent disposable water filters for your fridge to be a million-dollar industry it is today.

And I’m sure that if you value the health of yourself and your family, you want to know more about how exactly water filters work?

And is that simple activated carbon thing enough to take down E. Coli, Fecal Coliforms and other big (actually, tiny) baddies that give us diarrhoea and even some forms of cancer?


In this post I will tell you about…

  • What does the law say about water safety and filtration?
  • What contaminants are usually found in tap water?
  • What is the water filter inside your fridge made of?
  • How refrigerator filters work?
  • Is your water filter capable of removing all of the bad stuff in water?
  • How to select a quality water filter for your fridge?


All that and more, let’s get right into it…

The Current Safety Standards of Water Purification as Per U.S. law

Over 286 million Americans get their water from community water systems? Did you also know that over 7 million people fall ill due to contaminated water in the USA alone?

Well, now you do. The Safe Drinking Water Act (SDWA) was passed in 1974 with amendments in 1986 and 1996 to protect the drinking water in the US.

Because of the laws set by SDWA, the Environment Protection Agency (EPA) sets up some concrete standards for the quality of drinking water that must be enforced by the states, local administrations and water supplying mediums.

EPA has also set a maximum contaminant levels for drinking water and requires treatments for over 90 contaminants in drinking water for everyone.

At your local public water distribution system, water is subjected to many treatment methods like ultraviolet disinfection, reverse osmosis, wastewater reclamation and wastewater chlorination.

It is then taken for a round of chlorine disinfectant to be later distributed everywhere.

Common Contaminants Present in Tap Water!

EPA has released a list of over 90 impurities that is commonly found in tap water, they mostly are –

Chlorine – Since the 1850s, Chlorine is known to annihilate microorganisms which give us horrible diseases like diarrhoea, stomach infections etc.

Even though it is an excellent solution against many pathogens, prolonged contact with Chlorine is harmful.

Skin infections, irritations in mucous membranes and even forms of cancer can be some possibilities due to exposure to chlorine for a long time!

But the biggest issue with Chlorine is its taste. People in large numbers have reported to use water filters in the first place just because they hated the taste of chlorine in water.

Fluoride – Fluoride is a controversial issue and a topic of many conspiracy theories but the truth is that it has been stopped in water filtration for a long while now.

However, some places still use it and it could get mixed in naturally too.

But fluoride can easily be removed using even the most basic RO filtration, however, RO also eliminates beneficial substances in the water as well so it isn’t exactly a recommended filtration process.

Sediments – Dirt, silts, sands and other such natural elements cannot harm you much but they do make the appearance of water horrible.

Many water filters now have a sediment pre-filter to take care of this issue.

Chloride – Normal amount of Chloride is good for your blood pressure and overall health. But in excess, it makes the water taste salty. The Maximum Acceptable Level MAL of Chloride is 250 mg/L.

Any refrigerator water filter with NSF 42 certification is perfectly able to remove chlorine, its taste and other aesthetic impurities from the water supply.

Nitrate – Nitrate is harmless to humans unless it is in too much excess, then it can cause Methemoglobinemia (your hemoglobins won’t be able to carry oxygen!). The approximate MAL is 10mg/L.

Sulphate – Is completely harmless. It can make the taste of water a little bitter and might have some laxative tendency too when it is in excess. The MAL for sulphate is 500 mg/L. Sulphate is also rich with minerals.

Calcium, Potassium, Calcium and Magnesium – These are natural minerals and do not harm human beings in any way, even when taken in excess save for a few temporary irritations.

Heavy Metals (Copper, Lead, Arsenic etc) – Even though these too exist naturally in the ecosystem, they can be really dangerous to our central nervous, gastronomical and cardiovascular health.

The MAL for them should be less than a few ug/L.

Volatile Organic Compounds – VOCs along with PFAS (per- and polyfluoroalkyl substances) are found in agricultural water/industrial waste.

And they can get in your water supply. While most VOCs may or may not be harmful, PFAS certainly are. And they are hard to break down and can get accumulated inside you over time to damage your immune system.

Common symptoms of VOC and PFAS excess in your tap water are nausea, vomiting, eye-nose irritation, headache etc.

Just like heavy metals, the MAL of VOCs and PFAS should be under a few ug/L.

Pharmaceuticals – poorly controlled manufacturing facilities let pharmaceuticals enter into our water supply. It is very odd if someone ever catches any adverse effect due to pharmaceuticals in their water.

Even the most concentrated amount of pharmaceuticals detected were many magnitudes lesser than therapeutic dose.

Microplastics – We still haven’t figured out how to properly dispose of plastic waste and so sooner or later, plastic enters our water system and disintegrates into tiny particles.

The smallest of which has been reported to be 2.6 micron in size. It can’t be determined what microplastics can do to you but it’s better to be safe than sorry.

Total Suspended Solids – industrial waste, silts, decaying plants or other bio material that are larger than 2 microns are always found in water.

You rarely find them in drinking water but they can create problems for aquatic and stream health.

Pesticides and Herbicides – Most modern water filters are very much capable of removing herbicides and pesticides from your tap water.

It’s rarely in excess in your tap water but when it is, it can cause stomach infections typically.

Viruses and Bacteria – Usually, chlorine is perfectly capable of taking care of almost all kinds of bacteria and viruses. Unless there is some fault in your local water filtration facility, there should never be any case of virus or bacterial infection from your tap water.

pH – The normal range for perfect water balance is between 6.5 to 8.5. Any more and the water will become alkaline or basic, any less and it will become acidic.

What’s the Size of Various Substances Commonly Found in Tap Water?

The common substances found inside the tap water are measured in microns. 1 micron is one millionth of 1 meter. So, you can guess very few people have any idea of the size of these substances.

Did you know that naked human eyes can see small particles of 20 microns and above only? Those particles that are between 0.03 microns to 19 microns can only be seen with a microscope.

While those particles that are between 0.001 to 0.02 microns need an electron microscope to have a look at.

Below, we give some of the approximate sizes of various substances commonly present in tap water:

Common Substances in Tap Water

Size (in Microns)


0.003 – 0.05


0.03 – 30


100 – 1000


10 – 100


0.01 – 0.15


10 – 40


1 – 10


10 – 40


0.001 – 0.1


10 – 100


0.005 – 5

Industrial gases

0.2 – 0.4

Cement dust

4 – 100

Lung damaging dust

0.14 – 1.6

Human hair

30 – 120

Tobacco smoke

0.01 – 1


What is the Main Structure of Refrigerator Filters?

By now, you must want to know what exactly these handy fridge filters are made out of. Well, there are many videos out there that run a power saw through these things to show you the components inside.

They are fun to watch, I admit, but you will never know exactly what went in there.

The main component that does the actual job of filtering harmful substances from tap water is pure polypropylene (PP) shell and activated carbon.

Polypropylene (PP) has a high pollutant carrying capacity, it has a long service life and it’s really cost-effective too. Most refrigerator filters have charcoal activated carbon blocks that remove the most contaminants from your tap water.

However, in recent years, some manufacturers have started using coconut shell activated carbon blocks since their efficacy at absorbing pollutants from water is 50% more.

And so, the main component of a refrigerator stricture is a coconut shell activated carbon block with PP shell filter material.

What’s more, a coconut shell carbon block comes from a coconut shell as opposed to carbon blocks made from wood or coal which means it’s a renewable source material.

Coconut carbon material is taken from coconut trees that are found in tropical parts of the world where they can continue to keep giving coconuts for years.

Coconut shell carbon blocks also do not leave a taste like the other two since wood and coal both leak ash over time.


What Harmful Substances Water Filter Remove from Tap Water?


Here’s a list of contaminants that can be removed by a water filter from tap water:

  • Some filters can reduce lead
  • Some drugs
  • Hydrogen sulphide and some other volatile compounds that cause odors
  • 90% of Chlorine
  • Tannins
  • Lead
  • PFAS and VOC
  • Phenol
  • Chloramine
  • Smallamounts of metals, such as iron, mercury, and chelated copper

Some chlorine bi-products


What Substances Cannot be Removed by Water Filter from Tap Water?

Here is a list of the contaminants that the carbon blocks can’t remove –

  • Pharmaceuticals
  • Other inorganic sediments
  • Total Dissolved Solids
  • Ammonia
  • Nitrates
  • Nitrites
  • Sodium and most other cations
  • Significant amounts of heavy metals, iron, or copper
  • Significant amounts of hydrocarbonsor petroleum distillates
  • Few types of bacteria and viruses
  • Fluoride
  • Arsenic


How Does Coconut Shell Activated Carbon Filter Harmful Substances in Water?

But how does a water filter in your refrigerator filter out all those harmful substances? It’s all done by the coconut shell based activated carbon inside our water filter.

The coconut shell activated carbon uses two distinct methods to filter harmful substances from tap water, they are:


  1. 5micron Pore Filtration
  2. Adsorption Function of Coconut Shell Activated Carbons


  1. 5micron Pore Filtration –


The pore structure inside the coconut shell activated carbon (CSAC) is something different than other regular coal or wood-based carbon material.

The porosity of normal carbonaceous substances usually falls somewhere between 10 to 15 square meters of surface area per gram, by applying high temperature steam the porosity of such carbon materials can reach 1000 to 1200 square meters per gram.

That’s what an ‘activated’ carbon is.

And these activated carbons have a multiple size pores structure within for it is highly important that different sized pores remain in an activated carbon block to filter out various kinds of contaminants from tap water.

These pores are divided in Micro-pores (less than 2 nanometers), Meso-Pores (2 to 5 nanometers) and Macro-pores (about 50 to 200 nanometres) where 1 nanometer is 1 billionth of a meter.

In coconut shell based activated carbon blocks that we install in our water filters have more density of micro-pores than any other kind of activated carbon.

Coconut shell based activated carbon blocks have a marvellous 50% more surface area and porosity (50% more micro-pores) than any bituminous coal based activated carbon.


The pore function of CSAC uses 0.5micron pore filtration. The easiest explanation of the function of a 0.5micron pore filtration is that tap-water spreads over the porous surface area of the 0.5micron pores, the contaminants which are hydrophobic in nature attach with the CSAC surface and remain there while the filtered water continues forward.

This, more refined filtration is possible thanks to the size and volume of the pores themselves and since we distinctively use coconut shell based activated carbon that naturally have 50% more porous surface area than wood or coal based activated carbon with 50% more micro-pores the size of 0.5microns, the water is filtered more efficiently and quickly.


Substances That Can be Filtered With 0.5micron Pore Filtration –

There are many, many impurities that are or can get involved in your tap water. They could be physical impurities like heavy metal, soot, dust or they could be chemical impurities like pesticides, fertilizers etc.

But there is also the biggest threat in people’s minds which is biological impurity like bacteria, viruses. And then there is radiological impurity that can get in your tap water, yes, radiological contaminants like radon etc.

Your water filters are capable of removing harmful substances like soot, dust, chlorine, heavy metals, fibers, oils, sand, gravel, some viruses and bacteria and a few microplastics.

With our water filters you can get rid of radon, radium, lead, arsenic, chloride, nitrate, sulphate, lithium, fluoride, calcium, potassium, magnesium, sodium, herbicides, pesticides, silt, animal matter, sewage, pharmaceuticals and microplastics.

  1. The Adsorption Function of Coconut Shell Activated Carbon

Water filters work by entrapping harmful substances in tap water via three stages of filtration checks, they are –

  1. Particle Filtration

At this stage, water filters block all the heavy and larger substances that can be easily filtered such as sand, soot etc.


  1. Micro-Filtration

On this stage of water filtration, water filters capture smaller sized particles and substances like cysts and sugar.


  1. Adsorption-Filtration

At the final stage of water filtration, water filters use adsorption method to entrap microscopic substances like molecules, ions etc.

We know the mental picture about the first and second stages, but what is happening at the third stage exactly? What is the absorption method and how is it different from absorption?

First, let me tell you what is adsorption in easy language – when gas or liquid particles stick to the ascension or descension of the surface of a solid (usually) – that’s adsorption. Think of it like a magnet attracting a piece of metal but on a molecular level.

But there are two kinds of adsorptions happening inside your water filter – physisorption and chemisorption.

What is Physisorption?

Let me tell you what is physisorption – it’s when absorbate (substances in tap water) are attached with absorbent (activated carbon) due to weak intermolecular forces between them.

What Harmful Substances are Adsorbed by Physisorption?

Physisorption is able to remove most if not all organic matters such as radon, lithium, copper, lead (removable with NFS 52 certificate water filters), soot, dust particles, silt, total suspended solids, some pharmaceuticals, microplastics, even some fertilizers and can also remove unwanted odors and taste from the water.

What is Chemisorption?

And chemisorption happens when electrons are shared between the absorbate (water impurities) and absorbent (activated carbon), like a chemical reaction in your chemistry lab.

Chemisorption helps in filtering out harmful substances from the water using two methods i.e., Reduction and Decomposition.

Chemical Reaction of Reduction of Chlorine from Tap Water –

C* + NH2Cl + H20 → NH3 + H+ + Cl- + C*O Catalytic

Chemical Reaction of Decomposition of Chlorine from Tap Water –

C*O + 2NH2Cl → C* + 2H+ + 2Cl- + H20 + N2

What Harmful Substances are Adsorbed by Chemisorption?

Most inorganic substances that could not get removed by physisorption are finally removed by chemisorption method such as – chlorine ions, calcium, magnesium, sodium, gas ions, sulphate, pharmaceuticals, pesticides and herbicides etc.

Can an Old Refrigerator Filter Make You Sick?

Yes, absolutely. A study done in Germany on this stated that they found more harmful bacteria and substances from the water of an old filter than the tap water.

The activated carbon block inside any water filter is basically collecting harmful organic matters like bacteria away from the tap water. Eventually, the filtering block is chock full of nothing but harmful organic matters itself.

And that’s one heck of a breeding ground for all of them to multiply further which then leaks out into the “filtered” water. So, it is highly advised that people should change their refrigerator water filters every 6 months or 3 months if your home is getting its water supply from a private well because it has to clean a lot more sediments than public supply water.

In conclusion

To recap, SDWA and EPA has set a strict set of laws and guidelines for the filtration and drinking standards of public usage water.

Most common contaminants could be anything from harmless particles like dust, soot, silt, chlorine, calcium to something really harmful like PFAS, fertilizers, lead, bacteria and viruses etc. Their sizes vary and most commonly available refrigerator filters aren’t capable of purifying them completely!

We’ve seen that usual coal and wood-based activated carbon filters that are most commonly used in refrigerators are not up to the task and so we look for better solutions.

And the best answer to completely eliminate all harmful substances from your tap-water is to apply a coconut shell based activated carbon block which has 50% more micro pore structure and surface area.

A coconut shell based activated carbon uses 0.5micron pore filtration and adsorption methods of physisorption and chemisorption to both “magnetically” and chemically filter out more harmful substances than any other regular activated carbon water filters.

And if you do not change even the most prominent and advanced refrigerator water filters every 6 months, you stand to contaminate your water supply using the old water filters instead of purifying it, risking the health of your family drastically.

Congratulations, you just became a lot more aware about the water filters than most folks in this business. Feel free to share this blog with your friends and neighbors, educating them more on how they can - not get sick because of any waterborne diseases, like many other unfortunate ones.

Do you think it’s time to change that refrigerator water filter? Has it been six months since you installed them? Find out the best coconut shell activated carbon refrigerator water filters from your most trusted brands at cost effective prices.


Brand refrigerator water filter supplier

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