Glossary of Terms

Glossary of Terms

Here's a list of water-related terms that might help you understand our site better. It is compiled from a number of sources and should not be considered an "official" U.S. Geological Survey water glossary.


A form of organic whose particles have a large surface area with adsorptive quality, primarily used to remove chlorine, objectionable tastes and odors, and numerous organic compounds from water.

The process by which particles and molecular impurities adhere to the surface of activated carbon. This is typically done by electrochemical attraction.


A media included in every WaterMax product that includes silver to inhibit the growth of bacteria within the water softener or filter.

Brackish water contains a level of salt that is higher than freshwater but less than true saltwater found in oceans. Water containing between 1000 and 10,000 mg/L of dissolved solids is considered brackish. Over 10,000mg/L is salt water.

Our water softeners and conditioners require salt to properly function. The salt dissolves in water to create a saltwater solution, also known as brine. There is a dedicated brine tank as part of the system to house the salt and water used in this process.


Crushed and screened white marble media used in water treatment to neutralize acidic water. It dissolves into the water raising the pH level as well as slightly increasing the hardness level.

The number of contaminants that can be collected before the water softener, conditioner, or filter can hold no more. Once the product's capacity is reached, the system will need to be regenerated or the filter changed before the water can be treated again.

A family of synthetic materials based on cellulose used to make RO membranes. While CTA is superior to CA, under adverse water conditions both are effective in removing a wide spectrum of impurities from water. The disadvantage of Cellulose type membranes is that they are subject to bacterial attack, particularly in chlorinated water supplies. CTA has superior bacterial resistance.

Chemical complexes formed from the reaction between ammonia and chlorine. They are presently being used to disinfect municipal water supplies because unlike chlorine, they do not combine with organics in the water to form potentially dangerous carcinogens such as trihalomethanes (THM). Water containing chloramines cannot be used for fish tanks or kidney dialysis equipment.

A chemical in the form of liquid or gas used to disinfect water that is used by most municipal water treatment plants. This prevents bacteria contamination as the water is pumped to a home. High levels of chlorine in water can cause harsh odors and tastes, while drying out your skin. It is recommended to filter this chemical out prior to use in your home. It is known to react with organic matter in the water to form trihalomethanes (THM's), a suspected carcinogen.

Generally, water that has been treated by a water softener or water filter to improve its quality. Water softening removes hardness minerals like calcium and magnesium. Water filtration reduces a wide range of other contaminants. Often the term "water conditioning" involves both water softening and filtering.

A measure of the ability of a substance to transmit an electrical current. The conductivity imparted to water by dissolved solids is a function of both the amount and composition of the contaminants in the water and of the temperature of the water.

The length of time water is in direct contact with a surface. This is a major factor in determining how effectively impurities will be removed. The slower water passes through a media or filter material, the longer the contact time and the higher the likelihood of a contaminant being captured.

The control panel available on most point-of-entry water treatment products. This includes the electronics and technology that triggers sequences of operations based on the settings programmed into the circuit board.


Water which has been processed through both positively charged resin beads and negatively charged resin beads. This exchanges all of the charged molecules for hydrogen and oxygen molecules, leaving nothing but pure H2O as a result.

Process of making water biologically safe for human consumption by using chemicals, ultraviolet, ionization, etc., which destroys harmful microorganisms.

Water which has been purified using the evaporation-condensation cycle. It generally contains less than 5 ppm of Total Dissolved Solids.


The United States Environmental Protection Agency. This federal agency is responsible for safeguarding our environment, including public water supplies.


The pressure at which incoming water is supplied.

A term that refers to the water supply that is put into a water treatment system for processing (removal of impurities). This is often referred to as "raw" water.

The flow of water through reverse osmosis membranes, measured per square foot of surface.

The process of depositing impurities on the membrane surface of a Reverse Osmosis tap water filter, thus impeding normal function. This can be due to the presence of suspended solids or precipitated salts of biological growth. This causes a decrease in both the amount of water produced and the quality of the water.


A grain is a unit of measure that equals 0.065 grams. Another way to look at it is there are 7,000 grains in 1 pound. Grains per gallon measures the ratio of how much of a substance is inside of another, most often used when talking about hard water minerals.

Water located in the underground aquifers. It is the supply tapped by wells.


The amount of calcium and magnesium in the water measured in grains per gallon (expressed as calcium carbonate). This level is important to control to prevent scaling. Each grain is equal to 17.1 ppm of calcium and magnesium (expressed as calcium carbonate). These minerals typically enter a water supply through dissolved bedrock.

The chemical degradation of an RO membrane in water due to certain conditions such as high pH. Cellulose-based membranes are quite susceptible to hydrolysis while the TFC types are virtually immune.


An atom of any Total Dissolved Solid as it exists in water with a net electrical charge, positive (called cations) or negative (called anions).


A substance that can be found in many old pipes and fixtures. Lead has been found to be harmful to human development and should not be consumed. In order to reduce the amount of lead in a water supply, a filter that is certified for lead removal must be used.


The process of removing suspended particles from water by a straining action. The finest mechanical filters can remove bacteria by about 0.2 microns.

A term used for the type of material inside a water treatment system. Carbon is a media commonly used in water filters while resin is a media used in water softeners. A wide range of media exist and each has its specific purpose as to what they can remove from water.

A unit of length, one-millionth of a meter. The smallest particle that can be seen by the naked eye is about 40 microns across. The smallest bacteria are about 0.2 microns across. 1 micron = .00004 inches.

A common measurement for the flow rate of smaller Reverse Osmosis tap water filter systems usually measured with a graduated cylinder. One-thousandth of a liter per minute Milliliters/Min. x .38 = gallons per day.

The sum of the atomic weights of the individual atoms (from a periodic chart) that make up a molecule of a particular substance. Cellulose-based membranes can remove substances as light as MW of 300, while TFC-type membranes remove substances as light as MW of 200.

Homes built in urban areas have their water provided by the cities they live in. Water is treated at their plant, stored, and distributed through their infrastructure. They are required to remove any water contamination that may be harmful to your health, but may not remove issues that are considered "aesthetic" problems.


A contaminant that can affect how blood carries oxygen in the human body. It is usually introduced to a water supply through large amounts of agricultural or fertilizer activity. Consuming too much nitrate can be harmful, especially for babies and pregnant women.


Any of the compounds whose molecular structure is based on carbon. (E.g. carbon dioxide, wood, sugar, protein, plastics, methane, THM, TCE, etc.).

The natural tendency for water molecules to pass through a semipermeable membrane from the side that's low in dissolved impurities, to the side that's high in impurities.

The pressure created by the tendency of water to flow in osmosis. Every 100 ppm of TDS generates about 1 pound per square inch (psi) of osmotic pressure. This osmotic pressure must first be overcome by the water pressure for the RO membrane to be effective.


An emerging contaminant identified by the EPA as a health advisory due to evidence that it has caused adverse health effects. This family of chemicals is used during many industrial manufacturing processes and is commonly used in non-stick surfaces and fire-retardant foams. In order to reduce the level of PFOS/PFOA chemicals, you must use a water filter certified for this specific contaminant.

The parts of a contaminant per one million parts of water (e.g. one drop of chlorine dissolved in one million drops of water will give one part per million of chlorine in that mixture).

The acidity or alkalinity of water due to dissolved solids and measured on a scale of 1 to 14; 1 being most acid, 14 being most alkaline, and 7 being neutral.

Whatever alterations of the raw feed water required to prevent damage to a water treatment system. For example, a water softener may be necessary pretreatment of a Reverse Osmosis tap water filter to help protect the membranes from high levels of calcium.

Those pollutants that pose the most serious health hazards are determined by the Environmental Protection Agency (EPA). These standards must be met by water treatment facilities that provide drinking water to the public and are legally enforced.

Also known as treated water. This is the water that has been separated from the feed water stream by an RO membrane or other filtration material.


The amount of product water as compared with the total amount of feed water. This will give a measure of the efficiency of operation. For example, 10 gallons of feed water (if we separate 6 gallons into product water and reject 4 gallons), is a recovery of 60%.

The sequences of cycles that are performed when a water softener, conditioner, or filter has reached its capacity. The process includes backwashing and rinse cycles that will dislodge the contaminants collected and flush them down the drain, allowing the space for more contaminants to be collected after regeneration is complete. Water softeners and conditioners will require salt added to a brine tank in order to complete their regeneration, while most filters require only water.

The percentage of TDS removed from the feed water. Typically, more than 90% rejection is achieved with reverse osmosis.

The portion of the feed water that does not pass through the RO membrane, and which carries the remaining impurities to the drain.

Resin is a small polymer bead that is electrically charged. This charge acts as a magnet to attract and collect hardness minerals from water. Hague Quality Water uses a special type of resin called "Fine Mesh" that has a much smaller bead size. This allows for a more efficient collection process.

A reversal of the natural phenomenon of osmosis, brought about by the application of hydraulic pressure greater than the osmotic pressure in the water, causes the water molecules to flow through the membrane away from the dissolved substances.


A feature on some water softeners and conditioners that require salt to operate. The mechanism detects the concentration of salt inside the brine solution before it enters the media tank. If it is not above adequate levels, it provides an alert to remind the homeowner to add more salt for the best results.

See also: Turbidity. The sum of particles of dirt, clay, silt, and vegetation that float on (or are suspended in) water and can be removed by mechanical filtration.

Applies to special materials (both natural and synthetic) which allow certain substances -such as water -to pass through, while blocking or rejecting the passage of other substances such as dissolved solids and organics.

A water treatment device in which hard water is passed through a cation exchange material (resin) so that the calcium and magnesium are replaced by sodium, making it more desirable.

Water containing less than 1 grain-per-gallon of dissolved calcium and magnesium. Soft water has been proven to be better for water-using appliances, and gentler on hair and skin, while making soaps and detergents more effective too.

The most common practical configuration for an RO membrane in which sheets with a large surface area are wrapped in a spiral fashion to fit in a small space.


An organic material found in water that is caused by decaying plant matter. Water with tannins in it will have a brown color or a very musty/earthy smell. Tannins need a unique filtration process that uses anion resin to remove them from the water.

One of the more common toxic organic contaminants found in water. It is common in many homes, industrial environments, dry cleaning solvents, and cooking pans.

The most advanced reverse osmosis membrane made with a polyamide base polymer. It exhibits superior performance and immunity to adverse water conditions and is the only membrane material that is truly bacteria-proof.

A group of suspected carcinogenic organic compounds formed in water when chlorine (used as a disinfectant) reacts with naturally-occurring organic matter. For example, one of the most common THMs is chloroform.

Generally, the total amount of minerals and metals which are dissolved in water. The higher the TDS level, the more conductivity the water has.

Carbon-based chemicals which are frequently found in our water supplies and are harmful to human health. They are usually from agricultural and industrial effluents and hazardous waste dumps (e.g. TCE, PBC, DCBP, pesticides, etc.).

See also: Sediment. Suspended biological, inorganic, and organic particles in the water. It takes a sufficient amount to make the water seem cloudy.


The valve is a vital part of all Hague Quality Water products. It is where the incoming untreated water enters the system as well as where the conditioned water leaves the unit to serve your home. The unique design helps manage the directional flow of the water to ensure it is operating properly.


Homes that are located in rural areas most likely are receiving their water from a private well or surface water from a nearby lake or river. These water sources are more likely to have contamination issues caused by their surroundings. It is up to the homeowner to ensure that their water quality is acceptable.

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