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Home » Water Education & Testing » KDF Filter Media Guide (What Are They & How They Work)

KDF Filter Media Guide (What Are They & How They Work)

By: Craig Smith
Last Updated:

Have you been searching for a way to enhance the tap water in your home?

If you have, then you have probably noticed the presence of a KDH (Kinetic Degradation Fluxion) type filter in many water purification devices.

If you are not clear what role this type of filter plays in enhancing water quality, you are not alone by any means.

It’s one of the most misunderstood types of water filters.

As you read on, you will come to find that there is nothing fancy about these filters that use copper and zinc in their water purification process. They do, however, have a significant impact on the quality of the tap water that passes through them.

From my quarter of a century spent working in the swimming pool industry, I know the many benefits of using high purity metals in the water sanitizing and algae elimination process.

I will use that experience in this KDF Filter Media Guide to help explain what a KDF filter is, how they work, and discuss several other aspects of them.

What is KDF Filter Media?

kdf filter

This is a filter medium that’s used in many different types of home, industrial, and waste treatment water purification processes. KDF filters come in many sizes.

They can be used for small applications such as showerhead filters or they can be used for much larger tasks such as being a major component of a whole-house water purification system.

These types of filters are especially useful when it comes to reducing free chlorine levels and removing a large variety of heavy metals and inorganic compounds.

Although they are the main components of some types of stand-alone water filtration systems, they are best used in conjunction with other filter types. KDF filters are most commonly paired with some form of activated carbon filtration.

Variations of Granular KDF Media

As part of this KDF Filter Media Guide, it will also help you to know the different types of KDF granular filter media that exist. They are:

1. KDF-55

The main goal of this type of KDF filter media is the conversion of free chlorine into harmless chloride salt and to remove heavy metals from tap water. Not to be discounted is the fact that they will also inhibit algae and fungi growth and to a lesser extent the growth of bacteria and viruses.

This is the most common type of KDF granular filter media that is used as part of stand-alone and combination water filtration devices.

2. KDF-85

This type of KDF filtration media is used in water purification systems that target iron and hydrogen sulfide removal.

They will also remove many of the same heavy metals and free chlorine that KDF-55 filters do.

These can even be found in disk form which requires no backwashing and cuts down on the filter waste associated with the process.

3. KDF-F

KDF-F type filtration media targets chlorine and bacteria buildup in tap water. The big difference between KDF-F type filters and KDF-55 filters is that the granules are embedded in a fine mesh. This makes them ideal for placement inside activated carbon block filters.

4. KDF-C

This is just a much coarser mesh version of the above-mentioned KDF-F filter media. It’s designed to specifically target chlorine and heavy metals. It’s coarseness also allows it to be used in situations where less pressure drop is required.

How Does KDF Filter Media Work?

KDF filters are made using high purity granular forms of zinc and copper. These filters provide water purification based on a principle that’s known as REDOX (oxidation-reduction).

This is a naturally occurring electrochemical process that takes place when certain tap water substances such as free chlorine and heavy metals come into contact with KDF filter media.

When the tap water contacts the copper and zinc granules in the KDF filter media, ion exchange takes place. This happens between the tap water contaminants that KDF filters are effective on and this filter media’s embedded positively charged copper ions and negatively charged zinc ions.

This has a different impact depending on the specific type of water impurity that’s involved. For example, free chlorine is simply changed into harmless chloride salts and is allowed to pass through the system instead of being removed during the process.

Heavy metals bond with the filter media itself and thus are removed from the tap water altogether.

It’s a simple but very effective method of water purification that is widely popular.

What Contaminants Does a KDF Filter Remove?

Reverse Osmosis Water

Those that use KDF filters in the water purification process usually have two main objectives.

The first is to lessen harmful free chlorine and reduce its impact on tap water taste, looks, and smell. Some believe that KDF filters actually filter out free chlorine but as mentioned, they just convert it into a much less harmful form.

They also do a very good job of eliminating a variety of inorganic compounds and heavy metals that are commonly found in tap water. This includes the elimination or reduction of lead, iron, cadmium, mercury, copper, chromium, hydrogen sulfide, nickel, arsenic, and aluminum.

KDF filters will also somewhat reduce radon, sediment, and VOCs and to a lesser extent, they can reduce some dissolved solids in tap water.

They also inhibit algae, bacteria, virus, and fungi growth. This is because of the KDF filter media’s ability to quickly produce hydroxyl and hydrogen peroxide which are impactful on these types of microorganisms.

Where Are KDF Filter Media Used?

One of the reasons that these filters are so popular is that they offer nice water filtration benefits in several different types of situations.

You would be hard-pressed to find a type of RV water filter that did not contain some type of KDF filter media inside of it. The same goes for marine water filter applications.

They are also a major component of almost every type of under-sink or whole-house tap water filtration system. These work well in countertop style and refrigerator water filtration devices too.

KDF filters are also the filter media of choice for shower filters. That’s because they can withstand high water pressure very well and do not break down or shed their captured contaminants easily when hot water is passed through them.

Many hospital settings, industries, and restaurants also enjoy the many water-enhancing benefits that KDF filtration has to offer.

Advantages of KDF

kdf filter pros

Here are the main reasons why people like to use KDF filters as part of a stand-alone or complementary filter inside a water purification device.

1. They eliminate a large amount of free chlorine

These filters are excellent if you are supplied by municipal water where chlorine is used in its treatment. Most will eliminate 97% or more of free chlorine in tap water.

Free chlorine is the chlorine found in a water source that can still act as a sanitizer and can be harmful to the human body in large amounts.

2. KDF filters reduce heavy metals and inorganic compounds

They are a very good means of reducing heavy metals and inorganic compounds that are commonly found in household water. This includes being able to reduce cadmium, lead, iron, arsenic, mercury, chromium, hydrogen sulfide, and aluminum in tap water.

3. These filters can help extend the life of activated carbon filters

These types of filters are often used in the same filtration devices as activated carbon filters. Not only do they make a nice water filtration combination when used together, but they will also help to extend their partner activated carbon filter’s useful life.

KDF filters do this because they help keep bacteria and viruses from building up in activated carbon filters. These microorganisms are the main cause of shortened activated carbon filter life.

4. They work well with hot water and when under high pressure

KDF filters are one of the few filtration mediums that stay efficient when hot water passes through them. This is because unlike other types of filters, these filters do not break down or easily lose the contaminants they have captured when hot water passes through them.

5. It’s a recyclable filter medium

Their filter media is 100% Recyclable. This makes it an ideal water purification choice for those that want to lessen their carbon footprint on the planet.

Can be used in targeted types of water filtration

Because it comes in different granular forms, this type of filter media can be used in water filtration systems that are targeted to meet specific needs.

6. This filter type has a long useful life

KDF filters will last you a very long time before you have to replace them. Some will even last several years before they need to be changed out.

7. KDF filters are reasonably priced

When compared to many other types of water filters, KDF water filters are relatively inexpensive. This is especially true when you consider how long they last as was mentioned above.

Disadvantages of KDF

kdf filter cons

For as well as they work at removing some contaminants in water, KDF water filters do have some drawbacks. They are:

1. These types of filters do not remove organic compounds very well

This includes most pesticides, parasitic cysts, or disinfection byproducts. If these water impurities are a concern for you, then you will need a different or secondary means of water filtration.

2. They require periodic maintenance

Over time, heavy metals that KDF filters remove from tap water will build up inside of them. So they need to periodically have what is known as hot water ‘backwashing’ done to them.

This process not only wastes water but it’s possible for some of the dislodged contaminants in the filter to come out with the filtered water.

3. KDF filters do not remove chloramines

One of the biggest disadvantages of KDF filters is that they only remove what is known as free chlorine. That’s the potentially harmful type of chlorine that is still available to do its job as a sanitizer.

They cannot remove chloramines. That’s chlorine that has already acted as a sanitizer and is now in the form of hypochlorous acid, hypochlorite, or dissolved elemental chlorine.

Although chloramines are relatively harmless to the human body, they can still significantly impact tap water’s smell and taste.

KDF Filter FAQs

What Can’t KDF Remove?

Answer: They are not good at removing most parasitic cysts, pesticides, disinfection byproducts (such as chloramines), or other organic compounds. KDF filters are also not the main choice for the removal of total dissolved solids in tap water.

How to Determine Which KDF Media is Right for you?

Answer: As was mentioned above, there are 4 different types of KDF filter media. Although there is much overlap between them in what they can filter out, there are types that better meet specific needs.

So, compare your individual water filtration needs with what each one of the available KDF filter types does. Then choose the best match for what contaminants you are looking to filter out of your tap water.

What are the most common contaminants KDF removes?

Answer: A KDF filter’s main function with tap water purification is to reduce free chlorine, lessen inorganic compounds, reduce heavy metals, and inhibit bacteria, algae, virus, and fungi growth.

What’s better: activated Carbon or KDF?

Answer: It’s very hard to say which one of these is better. Both have strong points and weaknesses when it comes to water filtration. That’s why I always recommend that people purchase a water purification system that has both types of these filters included in it.

Here is a good example of a water purification system that includes both KDF and activated carbon filters.

A Few Final Words on KDF Filters

After reading this article you should now realize a few things about KDF filters. Most notable of which is that in most situations they only make an adequate stand-alone filter choice but offer many benefits when used as a complementary piece in a water filtration system.

I would even go as far as to say from what I know about KDF filters; I would make sure they were part of any whole-house or under-sink water filtration system that I was going to install in my house. They are also the preferred type of refrigerator and showerhead water filters.

So as you continue to shop for the best water filter to help purify the tap water that comes into your home, you should get more excited about those filtration systems that include KDF filter media as part of their makeup.

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Craig Smith
Craig got his start in water working in the swimming pool and spa industry. Water treatment would grow into his main career but he ended up working in the pool industry for over 26 years where much of his time was spent balancing the water in customer's swimming pools and installing water filtration equipment. Craig offers an abundance of water treatment knowledge after helping homeowners get pure water for 26 years.

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