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How the CuZn water filters work

On this page we hope to give you all the information you need to make an intelligent decision regarding the CuZn water filtering devices.

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To avoid the overview, jump to: Copper-Zinc Highlights


Oxidation/Reduction (Redox) is one of the most common reactions occurring in nature, but how it's used for water treatment remains a mystery to many water treatment dealers.

Redox media remove dissolved gases such as chlorine, hydrogen sulfide and methane from water. They can also remove virtually any soluble heavy metal, help prevent mineral hardness scale accumulation and reduce levels of microorganisms.

What makes these media unique, however, is that all the energy necessary to remove contaminants from water is inherent in the electrochemical and catalytic potential of the redox alloy. Because they're also versatile, they're a good choice for a wide variety of water treatment applications.


High purity copper-zinc redox media consistently remove 99 percent of free chlorine from drinking water by electrochemically reducing dissolved chlorine gas to water-soluble chloride ions. Because municipalities continue to chlorinate (and over-chlorinate) water, the market for dechlorination is growing.

Removing Heavy Metals

Removing dissolved heavy metals. Redox media remove up to 98 percent of water-soluble cations of lead, mercury, copper, nickel, chromium, cadmium, arsenic, antimony, cobalt and most other dissolved heavy metals upon direct contact. The removal mechanism is electrochemical and partially catalytic.

Soluble lead cations are reduced to insoluble lead atoms and electroplated onto the surface and interstices of the granular media. Metallic contaminants are bonded to the redox alloy until the filter materials are recycled in a copper smelter.

Controlling Micro-Organisms

The oxidation/reduction potential (ORP) shift from +200mV for untreated water to -500mV for water filtered through redox media controls microorganism growth. In general, different types of bacteria can only grow within a particular range of redox potential.

Water treated with one redox medium comprised of a copper-zinc alloy reduces bacteria and other microorganisms by disrupting electron transport, causing a cascade of cellular damage. Redox media also kill bacteria by direct electrochemical contact and by the flash formation of hydroxyl radicals and hydrogen peroxide, both of which interfere with a microorganism's ability to function.

Preventing Hardness Scale Accumulation

Redox alloy media prevent the formation and accumulation of mineral hardness scale, primarily calcium carbonate.

Electron microscopy and X-ray crystallography demonstrate that hardness scale from untreated water is formed by relatively large, irregularly shaped acicular crystals of calcium and magnesium mineral salts.

These salts form a hard, insoluble and interlocking network of vitreous limestone scale which plugs plumbing, interfering with heat transfer and damaging equipment.

Water filtered through redox alloy media alters the morphology of insoluble calcium and magnesium carbonate and sulfate crystals to relatively small, evenly shaped, rounded grains and rods. These form an unconsolidated powdery compound that won't adhere to metallic surfaces and is removed by 5-micron physical filtration.

Removing Iron

Redox filter media combine dissolved oxygen and soluble ferrous (Fe²)+ iron. The (Fe²)+ is catalytically removed on contact in the form of insoluble ferric hydroxide and ferric oxide. This also contributes to reducing iron, bacteria and the hydrogen sulfide byproduct from decomposing iron bacteria colonies.

Dissolved H2S gas gains an electron (reduction) while atomic copper from the redox filter media loses an electron (oxidation). The resultant copper sulfide is precipitated as a harmless insoluble ionic compound that's removed by backwashing.

The primary virtues of redox filter media are their synergistic compatibility with other point-of-use (POU) filter media including ion exchange resin, granular activated carbon, activated alumina, silver impregnated carbon and sodium hexametaphosphate. In fact, many POU devices are 1/3 redox filter media and 2/3 activated carbon.

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How CuZn Copper-Zinc Water Treatment Systems Work

The combination of copper and zinc (also patented under the trade name KDF®) in water treatment systems removes chlorine, chloramines, iron, lead, bacteria, hydrogen sulfide, and hundreds of other problem contaminants from the water supply. It also reduces scale and hardness.

Works Alone or in Combination

Copper-zinc can be used alone or in concert with traditional treatment processes (such as carbon and reverse osmosis) for a synergistic blend of media. Copper-zinc assists traditional treatment by extending the life of carbon or reverse osmosis membranes, by maintaining a bacteria-static environment inside the filter, and by leaving a residual of copper and zinc hydroxides in the treated water to discourage bacterial growth.

Lasts Longer than Carbon

With a lifespan of 10 to 20 times that of carbon, copper-zinc is the most efficient, longest lasting, and lowest maintenance filtration media on the market. It removes the weak link in most water treatment systems: the monitoring and maintenance and component replacement required by these systems.

CuZn systems perform better because the compact, dense copper-zinc alloy has no pores that plug up, is not soft like carbon, has no membranes to replace, remains bacteria static, and [the Single Tank and Double tank systems] can be easily back-washed for years of use.

Filters by Catalytic Action

CuZn media functions by catalytic action, using the age-old redox (reduction-oxidation) principle of dissimilar metals. Water containing dissolved oxygen, minerals, and organic materials enters a bed of the copper-zinc alloy, with the copper becoming the cathode and the zinc becoming the anode.

The space between each granule of alloy in the media bed becomes an electrolytic cell. The water and contaminants act as electrolytes.

As contaminants and oxygen pass through, a reaction takes place, causing zinc hydroxides and copper hydroxides to form in controlled amounts. These controlled releases of copper and zinc oxides (chelatable by the body) are carried into the filtered water and provide hostile conditions for algae, fungus, and bacteria growth.

Eliminates Hard Scale

Within a water system, calcium and magnesium can adhere to plumbing and water appliances by forming crystalline scale structures. These become hard, interfere with heat transfer and eventually cause loss of water flow and pressure.

Copper-zinc reshapes these hardness ions so they cannot adhere to each other or to the inside of plumbing. Instead the calcium and magnesium ions remain soluble in the water, thus reducing scale while adding life to the water.

(Water without these minerals is flat and can be aggressive, since water in its most natural state contains minerals such as calcium and magnesium, picked up from the earth as it filters through rock strata.)

This scale reduction feature is ideal for cooling towers, hot water heaters, water lines, plumbing, ice-makers, fountains, and other water-using equipment and appliances.

In other words: If you've a problem with moderated ''hard water'', the CuZn units will soften your water, although it is not a water softener. It will change the molecular shape of the Calcium crystal so that the calcium will be unable to adhere to a surface and will flow through in the water stream. In this way no scaling should occur and the water will behave like soft water.

We know of no systems, other than the CuZn, that will soften water without the need for salt or some salt-based regenerative material. The copper-zinc systems will soften the water without the need for salt, although it's limited to about 15 grains of hardness.

Removes Hydrogen Sulfide

Hydrogen sulfide is present in many U.S. water supplies. Recognized by its rotten egg odor and taste, it is a poisonous gas that can, in large amounts, cause nausea and illness or death. It is also corrosive to metals, which is especially serious in older plumbing systems that used lead-based solder.

When hydrogen sulfide passes through copper-zinc media, spontaneous oxidation removes the hydrogen sulfide by creating zinc oxides and zinc sulfates. Zinc oxides and zinc sulfates are defined as food supplements and nutrients by the Food and Drug Administration (FDA).

(During the copper-zinc filtration process, minuscule traces of zinc and copper are released into the water. In proper amounts, both copper and zinc are necessary for healthy body functions. The trace amounts found in CuZn filtered water are a small percentage of the minimum daily requirement for these minerals.)

Meets NSF, EPA Standards

In 1992, the Environmental Protection Agency (EPA) ruled that copper-zinc, patented as KDF, qualifies as a mechanical device. This means the media imparts nothing harmful to the water. The National Sanitation Foundation (NSF) tested KDF® and found it to be in compliance with its Standard 61 for water treatment plant applications and Standard 42 for aesthetic effects (taste, odor, chlorine reduction).

Removes Heavy Metals

Copper-zinc systems are excellent at removing heavy metals, often by electroplating them to the media's copper-zinc granules. Under normal circumstances, CuZn filtration removes 90 to 98% of heavy metals, including lead, iron, arsenic, and cadmium.

Works With Chlorination

When iron, hydrogen sulfide, or bacteria are present in large concentrations, CuZn filtration can be preceded by chlorination and retention time. Chlorination oxidizes these contaminants and assists the copper-zinc media in their removal. The copper-zinc, of course, then removes the chlorine and remaining contaminants from the water.

With carbon-only systems, this combination of chlorination and filtration is not efficient because the carbon is quickly depleted when high levels of chlorine pass through it.

Works With Carbon

Many CuZn systems use carbon filtration in concert with chlorination and copper-zinc filtration to treat water with high levels of organic contaminants which carbon is excellent at removing.

Because the carbon is not removing chlorine (the copper-zinc does this before the water reaches the carbon) and because the copper-zinc provides a bacteria-static environment, carbon's life is greatly increased. (Bacterial fouling of the carbon media is a serious problem in carbon-only water filtration and requires frequent media replacement.)

System Approach is One of the Best

Water filtration technology has reached the point where using a combination of treatment methods allows a system approach to water quality problems and provides better water quality.

CuZn has specialized in this approach since its start in 1987 by combining the most advanced copper-zinc technology with traditional filtration methods to solve a broad spectrum of water problems.

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BackWashing Frequently Asked Questions

Lots of folks have asked questions about the backwashing head on the CuZn Whole House Tank Systems (the Single Tank and Double tank units). Note: The inline units, cannot be backwashed. Here are the most commonly asked questions and answers.

Q: How many gallons does it use in the backwash?
A: Around fifty gallons. It could be slightly more or less depending upon water pressure.

Q: How long does the backwashing last?
A: It lasts approximately 10 minutes.

Q: What is the flow rate of the backwash water?
A: 5-7 gallons per minute flow rate

Q: Does it have to backwash every day?
A: It's advisable to backwash daily but not mandatory. Often times systems on municipally treated water backwash once every three or four days. Systems on wells are urged to backwash daily. The frequency of backwash depends greatly upon the quality of water.

The following applies mainly to the CuZn whole house InLine systems (WH10 and WH20)
Q: Is a pre filter neccesary to be installed before the CuZn system?
A: For Well water it's always recommended to use a sediment filter BEFORE the CuZn system, to insure it does not clog by sediments and particles. It would provide longer life for the CuZn system, since the larger particles would not need to be treated by the CuZn media. In many cases, the Automatic Self Cleaning 'auto-flush' filter would be a great choice. Some customers installed a standard type filter housing with sediment filters, Before the INLINE filter (and after).

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If you have any other questions about how the CuZn copper-zinc water filters can help you get your water treated, please feel free to contact us.

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