A Glossary of Water Filter Terms and Definitions – Filtering out the Confusion
by Gareth Marples
Have you done any research on the science and technology of water filters? Have you been doing your homework, preparing to buy the right water filtration system to fit your lifestyle? If you have, then you've probably been buried in technical terms. This glossary of water filter terms and definitions will filter out your confusion.
We're going to turn the confusing terms into simple explanations here. So relax and take it all in.
- The AG-TF membrane
The AG-TF membrane is a semi-permeable membrane in an RO unit that's resistant to chlorine.
Bacteriostatic refers to an environment where bacteria can grow. It's achieved in filter cartridges by incorporating certain chemical compounds into the filter media.
Brine refers to the water that's discharged by an RO unit.
- Bypass valve
The bypass valve, used to bypass some part of the filtration system, enables water to be diverted in a different direction than normal.
The canister is a two-piece unit, consisting of a head and a sump, that holds a filter cartridge.
Channeling refers to a condition that can develop in filters containing granular materials, usually carbon. Water flow produces small channels within the bed of media that allows the water to pass rapidly through the media without coming into contact with it.
- Check valve
A check valve is a one-way valve that allows water to flow only in one direction, thus preventing backflow in a filter system.
A contaminant is anything found in water, including microorganisms, radionuclides, chemicals, minerals, etc., which may be harmful to human health.
- CWS (Community Water System)
The CWS (Community Water System) supplies drinking water to 25 people or more year-round in their residences.
A disinfectant is a chemical (e.g. chlorine, chloramines or ozone) or physical process (e.g. UV light) that kills microorganisms such as viruses, bacteria and protozoa.
- Dual-membrane RO
A dual-membrane RO uses two membrane cartridges operating in parallel (side-by-side). They increase the production rate of an RO system, and are used frequently in RVs.
- Filter disk
The filter disk is a small disk built into some filters that serves to remove sediment. It has a very limited capacity, and once it gets plugged, the whole filter must be replaced.
- GAC (granular activated carbon)
GAC (granular activated carbon) comes in the form of small granules about 1/8-inch in diameter, and is used to improve the taste and odor of water.
- GPD (gallons per day)
GPD (gallons per day) measures the production of pure water from low-flow systems, such as RO and distillation.
- Granular carbon
Granular carbon is activated charcoal in small granular form. Filter elements are made by packing the granules into a housing. It's subject to channeling, and lower performance than solid-block carbon filters.
- Inorganic contaminants
Inorganic contaminants are mineral-based compounds such as metals, nitrates and asbestos, that naturally occur in some water, but can also enter water through human activities.
A microbe is a microorganism, usually disease-causing.
Microorganisms are tiny living organisms, only seen by microscope, that can cause acute health problems when consumed in drinking water.
- Non-transient non-community water system
A non-transient non-community water system serves the same people more than six months of the year, but not year-round.
- Organic contaminants
Organic contaminants are carbon-based chemicals, such as solvents and pesticides, which enter water through cropland runoff or discharge from factories.
Ozonating refers to the process that introduces ozone into water, either by injecting the gas or by creating it via exposure to UV light. It subsequently kills microbial contaminants.
A pathogen is an organism that causes disease.
Permeate, sometimes called product water, is another term for the pure water produced by an RO system.
- Polishing filter
The polishing filter is the last filter in a series that gives the water a final treatment, usually a carbon taste-and-odor unit.
- PWS (Public Water System)
A PWS (Public Water System) supplies drinking water to at least 25 people, at least 60 days each year.
Radionuclides are any man-made or natural element that emits radiation, and that may cause cancer after many years of exposure through drinking water.
- RO (Reverse Osmosis)
RO, or reverse osmosis, is a process for purifying water.
- RO membrane
The RO membrane, a replaceable cylindrical cartridge, is the part of the RO system that actually filters the water.
The restrictor is the part of an RO system that controls the amount of water that passes through the unit.
- Sensitive subpopulation
The sensitive subpopulation refers to those people who may be more vulnerable to drinking water contamination, such as infants, children, some elderly and people with severely-compromised immune systems.
- Source water
Source water refers to water in its natural state, before any treatment for drinking (i.e. lakes, streams, ground water).
In a canister assembly, the sump is the part that screws into the head and holds the cartridge.
- Surface water
Surface water is pumped and treated from sources open to the atmosphere, such as rivers, lakes and reservoirs.
T&O refers to taste and odor.
- TDS (total dissolved solids)
TDS (total dissolved solids) is a measure of calcium, magnesium and other dissolved mineral salts in drinking water, used when testing RO output.
- Transient non-community water system
A transient non-community water system serves the public, but not the same individuals, for more than six months.
- Vulnerability assessment
A vulnerability assessment is an evaluation of drinking water source quality and its vulnerability to contamination by pathogens and toxic chemicals.
There – that should do it. We've covered the different types of water filters, along with the contaminants that make if necessary to have a water filter. And we've also covered the different types of systems in different geographical areas. We've filtered out the confusion so you can choose the water filter that best suits your location and your lifestyle.
Take your expertise and get that water filter installed, no matter which one it is. Then sit down, relax and be confident that you're drinking safe, pure water.