Water Glossary

specifically aqueous acids have pHs less than 7 because the concentration of hydronium ions is greater than 10-7 miles per liter. Acidic water will stain copper pipes blue or green and rust iron pipes. Additionally, acidic water will corrode water fixtures, and cause pinhole leaks and pipe failure.
is a filtration process in which contaminants in water are attracted to and bond to a filter media, such as activated carbon.
is a herbicide that enters the water supply through runoff and leaching. Exposure to alachlor can cause skin and eye irritation as well as cancer and liver/kidney damage.
is a strong and fireproof silicate-mineral fiber. The major source of asbestos in drinking water is from decaying cement water mains and the erosion of asbestos from naturally occurring deposits into surface and ground water. It can also be found in some appliances, including broilers, slow cookers, waffle irons, dishwashers, and refrigerators. Long-term exposure to asbestos has been linked to lung disease and other types of cancer. Filtration methods such as UV light and granular activated carbon filters do not remove asbestos. However, solid block activated carbon, reverse osmosis systems, and ceramic filters can effectively remove the fibrous mineral.
is a herbicide and plant-growth stimulator that enters the drinking supply through runoff and leaching. Short-term exposure to atrazine can lead to heart, lung, and kidney congestion, low blood pressure, muscle spasms, reproductive difficulties, and cancer.
reverses the flow of water through a filter media to remove accumulated debris and particles. Backwashing filtration is often the final step in more complex treatment systems.
are tiny, single-cell organisms that are ubiquitous in our environment and water. While some bacteria are harmless, others can cause serious waterborne diseases, such as typhoid fever, dysentery, gastroenteritis, and cholera.
are made from highly purified, silver-bearing inert material mixed with powered activated carbon material. The silver ions in the filter prevent bacterial growth in and on the filter media. While a filter that is not bacteriostatic should be replaced at least every 6 months, a bacteriostatic filter can last 5 or more years. The only limit on the life of a bacteriostatic filter is the size of the media bed, which determines how much it will be capable of absorbing and adsorbing. Bacteriostatic filters are often used in combination with KDF (Kinetic Degradation Fluxon Media) systems.
is a volatile organic compound discharged from petroleum and chemical industries. Benzene is a known carcinogen and has been associated with myeloid leukemia (AML), miscarriage, and damage to reproductive and blood-forming organs.
is the most common cation (positively charged ion) in water, and, together with magnesium, is a major component of hard water. While calcium in drinking water generally is not a health issue, it can cause significant damage to plumbing pipes and fixtures.
is a process of filtering that uses activated or charged carbon to remove pollutants from water. Used as a primary filter or pre-filter, activated carbon effectively removes volatile organic compounds (VOCs), pesticides, and herbicides, chlorine, benzene, trihalomethane (THMs) compounds, radon, solvents, and other man made chemicals. Carbon filters are less successful at removing dissolved arsenic and some heavy metals. There are two main types of carbon filters, granulated carbon and solid carbon block filters. Solid carbon block filters are typically more expensive but they last longer and capture everything granulated filters do, including more chemicals.
is an organic, plant-based filter material with varying sizes and shapes of rough fibers. The fibers reduce unwanted taste and odor, particularly chlorine taste and odor. It also filters sediment, silt, scale particles, rust particles, and extra-fine dirt. There are different types of cellulose, including cellulose acetate, nitrocellulose or cellulose nitrate, and regenerated cellulose. While cellulose D-10 is a natural fiber that may be weakened by bacteria found in untreated water, synthetic cellulose, such as cellulose D-15, is resistant to bacteria.
is a combination of chlorine and ammonia and is sometimes used in place of chlorine to disinfect water supplies. Chloramine can cause or aggravate respiratory and skin problems and contribute to digestive and kidney diseases.
forms when chlorine adds one electron to form a negatively charged ion (anion). Chloride helps maintain the acid-base balance in the human body and is essential for sustaining human metabolism. Chloride is found in almost all natural water sources, though its concentration varies according to geographic region. Chloride in drinking water does not pose any significant health hazards. However, because chloride increases the electrical conductivity of water, it can increase its corrosivity.
is a disinfectant added to public water supplies to kill bacteria and viruses. Chlorine reacts with other naturally occurring organic and inorganic matter in the water which forms toxic byproducts called trihalomethanes or THMs. THMs have been linked to a wide range of serious health problems, including asthma, cancer, kidney, liver, and nervous system damage, as well as birth defects.
is a metal that is commonly used to make electrical wiring and plumbing material. Copper in tap water has been linked to severe systemic diseases, such as copper induced liver cirrhosis and kidney disease.
is microorganism that is highly resistant to disinfectants, including chlorine. Commonly found in lakes and rivers, it has caused several significant outbreaks of gastrointestinal illness.
are chlorine-resistant microscopic parasites, such as giardia and cryptosporidium. Symptoms of infection include diarrhea, abdominal cramping, vomiting, fever, headache, and loss of appetite.
is the process of removing ions from water via ion exchange. In the deionization process (also known as demineralization), water passes through two resins. The first resin removes positively charged ions (cations). The second resin removes negatively charged ions (anions). Because a large number of dissolved impurities in water are ions, such as sodium, chlorides, calcium, etc., the deionization process yields high purity, deionized water that can be used in countless applications, including laboratories, medical, cosmetics, electronics manufacturing, plating, and other industrial processes. Deionization does not remove viruses, bacteria, or uncharged organic matter.
is a filtration process that separates water and contaminants by boiling water until the water vaporizes. While the water vapor is directed to a condenser where it returns to a liquid, the contaminants remain behind in a solid state. However, some pollutants that boil at a lower temperature than water are not removed.
is a government agency whose purpose is to establish and enforce maximum contaminant levels for all municipal water plants in the United States.
is a Federal statute governing the registration, distribution, sale, and use of pesticides in the U.S. According to FIFRA, a pesticide is defined as “any substance or mixture of substances intended for preventing, destroying, repelling, or mitigating any pest.” In addition, FIFRA defines “pest” to include “(1) any insect, rodent, nematode, fungus, weed, or (2) any other form of terrestrial or aquatic plant or animal life or virus, bacteria, or other micro-organism (except viruses, bacteria, or other micro-organisms on or in living man or other animals).” Before a pesticide substance or product can be sold in the U.S., it must be registered with the EPA and adhere to the proper labelling requirements. The overall objective of FIFRA is to ensure that pesticides will not generally cause unreasonable risk to people and the environment. After an influx of virus and bacteria-reduction claims in mid-2019 after the start of the COVID-19 pandemic, the EPA cracked down and began heavily enforcing FIFRA, particularly on online markets such as Amazon. Any listings using pesticide keywords that do not have an EPA registration number must be updated to either remove the offending terms or provide the EPA registration and labelling.
is a term that describes the general process of separating water and contaminants by using a medium, such as active carbon or other porous film.
is a chemical compound derived from the element fluorine. Fluoride is added to drinking water and toothpaste in an attempt to strengthen teeth.
is a federal agency that monitors and inspects bottled water and bottled water processing plants. Under FDA regulations, bottled water is not required to be any safer than tap water. Additionally, the FDA does not require bottled water companies to reveal where they obtained their water, how they treat their water, or what contaminants are found in the water.
is low-lathering water that contains high levels of metal ions, such as calcium and magnesium. Though hard water is generally considered safe to drink, it can cause scaling or corrosion in plumbing and appliances.
are metals with a high relative atomic mass, such as copper, lead, mercury, and arsenic. Heavy metal contaminants have been found in most drinking water sources, such as wells, lakes, rivers, municipal water systems, and even glaciers. Exposure to heavy metals has been linked to cancer, organ damage, autoimmune diseases, reproductive system damage, and learning disabilities.
is an atom or group of atoms in a solution that is either positively charged (cation) or negatively charged (anion). Positively charged ions are attracted to negatively charged ions and vice versa. Certain water treatment systems, such as water softeners and deionizers, treat water by exchanging ions to neutralize contaminants.
is a process of changing the molecular structure of drinking water contaminants by trapping and splitting their ions, which creates a less hazardous molecule.
attract the positive ions in drinking water, which creates alkaline water full of negatively charged ions. Alkaline water is said to be not only a powerful antioxidant but also an effective way to restore the acid/alkaline balance in the body.
is the most common element on Earth and occurs naturally in ground water in three forms: 1) ferrous iron (clear water iron) 2) ferric iron (red water iron), and 3) heme iron (organic/bacteria iron). A water softener can remove ferrous iron under certain conditions; otherwise, ferrous iron can only be removed by converting it to ferric iron, which then can be easily filtered by mechanical filtration. Heme iron can be removed by an organic scavenger anion resin or by oxidation with chlorine followed by mechanical filtration. Only an iron reduction system can remove all three types of iron
are atoms of the same element that have different numbers of neutrons.
is a filter with a medium made from granulated copper and zinc alloys. The copper and zinc encourage redox, or reduction oxidation, in which harmful contaminants lose an electron, rendering the contaminant harmless. KDF-55 is designed specifically to remove chlorine, microbiological contaminants, and heavy metals.
is a filter made from copper-zinc granules that effectively remove iron and hydrogen sulfide.
is a poisonous heavy metal that enters the water supply in several different ways, most notably through pipes, solder, faucets, and coolers. Lead exposure in children and infants can have catastrophic results, including reduced attention span, behavioral problems, delays in physical and mental development, and death. In adults, lead exposure can cause kidney damage, brain and central nervous system damage, and high blood pressure.
is an insecticide as well as a therapeutic pesticide used to treat scabies in humans and animals. Short-term exposure can lead to high body temperature and pulmonary edema, while long-term exposure can lead to nervous disorders, cancer, and liver damage.
is the eighth most common element in the Earth’s crust and is highly soluble in water. Magnesium is important to nearly every function in the human body, including aiding in the contraction and relaxation of muscles, the production of protein, and the production and transport of energy. Side effects from increased magnesium are rare because the body is able to readily remove excess amounts. Magnesium and other alkali metals are responsible for water hardness.
is a naturally occurring mineral and a common trace element in the human diet. It becomes noticeable in drinking water at 0.05 milligrams per liter (ppm) of water. Manganese is generally not harmful until levels are 10 times higher than this. Exposure to high levels of manganese has been associated with toxicity to the nervous system, which produces symptoms similar to Parkinson’s disease. Bottle-fed infants, children, and pregnant women are more susceptible to high levels of manganese in drinking water. Signs of high levels of manganese in drinking water include brownish-red discoloration, an off-taste and odor, and water that stains plumbing fixtures or clothes.
is the maximum level at which a contaminant can occur without risk to human health. According to the EPA, this goal is not always economically or technologically feasible, and it cannot always be enforced.
is a chemical initially added to gasoline to reduce air pollution. While its use is declining, MTBE commonly enters the water supply through leaking fuel storage tanks and pipelines.
is a nonpartisan, nonprofit advocacy group whose goal is to protect the planet’s natural resources, including drinking water. With a staff of over 300 scientists and other specialists, the group is often involved in legal issues concerning drinking water regulations.
is an international, nonprofit organization that provides independent certification for water purification devices, bottled water, water softeners, and other food preparation systems. The NSF also assesses water filtration advertisements for accuracy and truthfulness.
is a certification that is concerned with improving drinking water by reducing specific aesthetic or non-health-related contaminants (odor, taste, chlorine, and particulates) that may be in the water. This certification applies to drinking water filtration devices, such as carbon filters.
is a certification that is concerned with improving drinking water by reducing specific health-related contaminants such as cysts, lead, VOCs, and MTBE that may be in the water. This certification applies to drinking water filtration devices, such as carbon filters.
is a certification that evaluates reverse osmosis systems, including contaminant reduction claims.
is a certification that evaluates the chemicals in water treatment processes. Specifically, the standard evaluates 1) if the water treatment chemicals are safe at maximum dose, and 2) if impurities are below the maximum accepted levels. The standard evaluates the health effects of water treatment chemicals such as corrosion and scale inhibitors, softening chemicals, disinfection and oxidation chemicals, and more. It only addresses human health effects of products and not environmental effects.
is a certification that water products, such as pipes, fittings, water filter faucets, and reverse osmosis faucets, do not leach contaminants into the water.
is a certification that a shower filter effectively reduces chlorine from the water supply. In order to receive this certification, chlorine removal must be at 50% or greater.
is a certification that evaluates how well water filtration products remove a variety of emerging contaminants. Emerging contaminants include certain prescription drugs, over-the-counter medications, herbicides and pesticides, and chemical compounds (such as BPA and flame retardants). This certification applies to drinking water filtration systems such as carbon filters.
is a filtration process that creates ozone, a reactive and unstable gas that oxidizes or destroys all bacteria, mold and yeast spores, viruses, and organic materials. Ozonation also oxidizes and precipitates iron, manganese, and sulfur, enabling them to be filtered out of a solution. Additionally, certain chlorine resistant pathogens cannot multiply in water that has been treated with ozone.
are particles of sand, dust, rust, and sediment in drinking water. Water contaminated with particulates often tastes “dirty” and appears cloudy. Particulates can carry toxic microbiological, inorganic, and organic contaminates through the water system.
are a group of over 4,700 man-made chemical substances used for industrial purposes and consumer products due to their unique properties of oil and water repellence, temperature and chemical resistance, and surfactant properties. They are pervasive and common in the environment due to degradation resistance, and are associated with a number of health problems, such as including liver, kidney, and prostate cancers; thyroid diseases; other liver and endocrine system problems; developmental effects; reproductive issues; high cholesterol; reduction in immune system response; pregnancy-induced hypertension and preeclampsia; and low birth weight in newborn babies.
is a man-made chemical substance belonging to the substance class PFAS. PFOA and its salts are used in industrial processes and commercial products, such as for stain and water resistant coatings and non-stick coatings. PFOA exposure has associations with high cholesterol, increased liver enzymes, decreased vaccination response, thyroid disorders, pregnancy-induced hypertension and preeclampsia, and testicular and kidney cancers.
is a man-made chemical substance belonging to the substance class PFAS. PFOS and its salts and precursors are used in industrial and household product manufacturing, including for fire fighting foams and coatings for fabrics, leather, and food packaging. PFOS exposure has associations with high cholesterol and adverse reproductive and developmental effects.
is a scale that measures the degree of alkalinity or acidity of a solution. Numbers below 7.0 represent acidity, while numbers above 7.0 represent alkalinity.
are a group of toxic synthetic chemicals that are commonly used in plastics. Because phthalates are nearly ubiquitous in our society, they are commonly found in drinking water. When ingested, phthalates act as endocrine disrupters, which can lead to lower sperm count, testicular atrophy, reproductive abnormalities, and breast cancer.
systems or whole-house water filters connect to the incoming water supply and filters all the water that enters a home, including water that goes to the sink, bath tubs, showers, refrigerators, and laundry rooms.
systems are filters installed at the point of consumption and include drinking water filters, reverse osmosis, and shower filters.
is a unit of measurement for the amount of pressure exerted on an area of one square inch. Filters, such as a reverse osmosis filter, require a certain range of water pressure for the filter to work effectively.
is a type of filter design that channels water through a radial pattern from outside of a filter element into the center core. In contrast to axial flow, in which water enters one end of the cartridge, flows the length of the cartridge, and then exits through a center hole at the other end, radial flow uses the entire surface of the carbon. The increased surface area allows for greater water flow with less pressure loss. Additionally, radial flow reduces the release of carbon fines typically associated with granular activated carbon (GAC) filters.
occurs when the electrons of two molecules are exchanged. This transfer changes the molecular make-up of a contaminant, which renders it less dangerous.
is a filtration process that forces water through a selective membrane, which leaves dissolved salts and contaminants on one side of the filter and purified water on the other side. This is the reverse of osmosis, in which a solvent moves through a membrane from an area of low solute concentration to an area of high solute concentration.
forms when free iron is exposed to oxygen and water. Rust in drinking water typically comes from water mains, water pipes in a home or building, or it can occur naturally in well water. Rust can cause water to appear red, orange, or yellow, depending on the different states of oxidation of iron (rust) and its concentration in water. At high levels, it can stain laundry and fixtures or contain enough iron to be health concern. Water containing rust can also indicate that the water is corrosive.
unlike traditional ion-exchange water softeners, do not remove minerals such as calcium and magnesium, to “soften” the water. Consequently, salt-free water softeners are technically not water softeners. Instead, salt-free water “softeners” merely prevent minerals from depositing on the insides of appliances and pipes, much like a descaler or scale inhibitor.
prevents scale formation and corrosion that can help extend the life of pipes and plumbing fixtures. While a water softener replaces hard water ions (primarily calcium ions) with soft water ions (sodium ions) a scale inhibitor changes the way hard ions stick together so that they will not cling to pipes or other plumbing surfaces. Scale inhibitors require little maintenance and are cheaper to install than water softeners.
is soil, sand, and minerals that settle on the bottom of lakes, streams, and rivers. Human or natural activity can stir sediment back into the water, causing turbidity. While sediment itself may not be harmful, it can carry harmful microbiological, organic, and inorganic contaminants.
remove suspended material from drinking water including sand, silt, clay, and other organic materials that can cause turbidity and cloudiness. Sediment filters do not remove nitrates, heavy metals, pesticides, trihalomethanes, or microbial contaminates.
is a filtration process that removes contaminants but not minerals from drinking water. In contrast to selective filtration, reverse osmosis and distillation remove both contaminants and minerals from drinking water.
is a metallic element that is listed on the EPA Drinking Water Contaminant List. It is listed as a contaminant because high levels of salt can be dangerous for those with high blood pressure, pregnant women, and individuals who have difficulty excreting sodium.
is water in which the calcium and magnesium ions have been replaced by sodium ions. Soft water typically helps soap lather readily and does not build up scale in water products, such as boilers or hot water heaters.
is a common, multivalent non-metal that is essential to life. When bacteria feed off the sulfur in decaying plants, rocks, and soil, they create as a byproduct hydrogen sulfide gas. While hydrogen sulfide gas is most often found in wells, both deep and shallow, surface water has less hydrogen sulfide as the gas is readily released into the air. Water heaters may also contain hydrogen sulfide gas if dissolved sulfur reacts with a magnesium rod that is often placed in water heaters to prevent corrosion. Hydrogen sulfide is not a health hazard, though it has a “rotten egg” odor that requires treatment. Additionally, water supplies with as little as 1.0 ppm (parts per million) of hydrogen sulfide can be corrosive and may tarnish copper and silverware.
are man-made chemicals that include volatile organic compounds, pesticides, herbicides, polychlorinated biphenyls, and treatment chemicals. Many synthetic organic chemicals are linked to an increase risk of cancer, nervous system damage, and hormonal disruption.
is a measurement of a number of different substances found in water which may not be removed by a filter with a micron of 2 or higher. In drinking water, TDS typically consists of dissolved minerals, phosphates, and nitrates, largely present in the water from soil and rock erosion and/or residential and agricultural runoff. TDS is generally not considered a water contaminant and is not associated with any specific health effects.
is used to remove grease from fabricated metal parts and other textiles. Ingesting TCE in drinking water can lead to liver damage and cancer.
are the carcinogenic byproducts of the disinfectant chlorine. Exposure to THMs has been associated with atherosclerosis, cancer, and miscarriage.
describes the cloudiness or haziness of water due to undissolved particles such as sand, clay, silt, or suspended iron. Turbidity can cause staining and discoloration in sinks, fixtures, and fabric.
disinfect by exposing water to UV light. The UV light kills bacteria, viruses, some cysts, Giardia lamblia, and Cryptosporidium cysts by rearranging their RNA/DNA. It does not kill Giardia lamblia cysts or Cryptosporidium parvum oocysts and is not recommended if the untreated water contains high levels of coliform. The amount of organisms killed depends on the contact time the light has with the water, the intensity of the UV light, and the amount of solid particles in the water. Its primary advantage is that UV light disinfects water without creating new chemical processes, changing the odor or taste, and it does not remove any beneficial minerals. Its primary disadvantage is that it lacks residual or continuing disinfection. UV devices can either be point-of-use or point-of-entry.
is an independent, non-profit laboratory that conducts a wide range of testing and certification services for water product manufacturers, including those who manufacture water filters and plumbing products. It is one of the most recognized certifiers in the United States.
are microscopic infectious agents that use a host cell to reproduce. Viruses such as hepatitis A, rotavirus, and Norwalk can be found in drinking water supplies and can cause serious illness.
are synthetic chemicals such as insecticides and herbicides, chlorinated solvents, and fuel. VOCs move easily through the environment and have been associated with an irregular heartbeat, nervous system damage, and cancer.
is an annual report issued by local community municipal systems. It is legally required to provide consumers with detailed information about the sources of drinking water, treatment methods, and contaminants.
is the origin of water in a water supply system. Large-scale water supply systems rely primarily on surface water, which include rivers, lakes, and reservoirs. Smaller systems rely on ground water, which are typically pumped from wells fed by aquifers (underground porous rocks or sand that collect water).
primarily rely on ground water, which can be contaminated by seepage through landfills, failed septic tanks, underground fuel tanks, fertilizers and pesticides, and runoff. Although the EPA does not regulate wells, it is still critical that wells are checked regularly to ensure that the water is safe to drink.
Back to Water Filters FAQs