Reference

Water treatment glossary

Every technical term on this site, explained in plain English. Search it, or jump by letter.

A

Activated carbon Filtration

A porous carbon media that grabs chlorine, tastes, odors, and many organic chemicals as water flows through it. 'Catalytic' carbon is a tougher grade that also helps break down sulfur and chloramine.

Air-injection oxidation (AIO) Treatment

A chemical-free method that draws a pocket of air into the tank so dissolved iron, manganese, and sulfur oxidize into particles the media bed can trap. No salt or chemicals to refill — just a periodic backwash.

See also: Oxidation , Iron filter , Backwash

Anion exchange Treatment

A whole-house treatment that passes water over a resin bed which trades chloride ions for negatively charged contaminants like nitrate. It works like a softener but targets nitrate instead of hardness. A nitrate-selective resin is a special version that grabs nitrate ahead of sulfate, so high-sulfate water does not cause the resin to dump nitrate back into your water.

Anion exchange resin Treatment

A resin bed that removes negatively charged contaminants like tannins by swapping them for chloride ions, then recharging with ordinary salt. It is the standard whole-house fix for tannins, and works like a softener tuned for a different target.

See also: Tannins , Ion exchange , Water softener

Arsenic Contaminant

A naturally occurring, tasteless toxic element found in some wells. There is no smell or color to warn you, so a lab test is the only way to detect it. The EPA limit is 10 ppb (parts per billion).

B

Backwash Maintenance

A self-cleaning cycle where the system reverses water flow to flush trapped contaminants down the drain. Backwashing filters keep working without cartridge changes but use some water and need a drain line.

Brine Maintenance

The concentrated salt solution a softener uses to recharge its resin, and the salty wastewater it sends to the drain during regeneration.

C

Chlorination Treatment

Adding chlorine to disinfect water or to oxidize iron and sulfur. 'Shock' chlorination is a one-time dose to clean out a contaminated well; continuous injection is an ongoing feed.

Coliform bacteria Contaminant

A group of bacteria used as an indicator: finding them means surface contamination has reached your well and other germs may be present too. The fix is disinfection — usually UV or chlorination.

D

Disinfection byproducts (DBPs) Contaminant

Compounds such as trihalomethanes that form when chlorine reacts with organic matter like tannins in water. The EPA regulates them in public water because long-term exposure is linked to higher cancer risk.

F

Flow rate (GPM) Units

How much water a system can pass without dropping your pressure, measured in gallons per minute (GPM). A whole-house filter must match your home's peak demand — often 7–15 GPM — or showers and taps run weak.

G

Grains per gallon (gpg) Units

The standard U.S. unit for water hardness. One grain per gallon equals about 17.1 parts per million. Water under 1 gpg is soft; over 7 gpg is hard; over 10.5 gpg is very hard.

H

Hardness Water chemistry

How much dissolved calcium and magnesium your water carries. Hard water leaves chalky scale on fixtures, spots on glasses, and makes soap lather poorly. It is measured in grains per gallon (gpg) or parts per million (ppm).

Hydrogen sulfide Contaminant

The gas that gives well water its rotten-egg smell. It is removed by oxidation — adding air or another oxidizer so the sulfur turns solid and filters out.

I

Ion exchange Treatment

The chemistry inside a softener: water passes over a bed of resin beads that trade the hardness minerals (calcium, magnesium) for harmless sodium or potassium ions.

See also: Water softener , Hardness , Brine

Iron (ferrous vs. ferric) Contaminant

The metal behind rust stains on fixtures and laundry. Dissolved 'ferrous' (clear-water) iron is invisible until it hits air; 'ferric' (red-water) iron has already turned to rust and looks orange. Each is removed differently.

See also: Oxidation , Iron filter , Iron bacteria

Iron bacteria Contaminant

Harmless-to-drink but troublesome microbes that feed on iron and leave a slimy, rust-colored buildup in tanks, toilets, and pipes. They usually need shock chlorination on top of an iron filter.

Iron filter Equipment

A whole-house system that oxidizes dissolved iron into rust particles, then traps them in a media bed and flushes them out on a backwash cycle. Many also handle manganese and sulfur.

M

Manganese Contaminant

A naturally occurring metal that dissolves out of bedrock into well water, often alongside iron. It leaves black or dark-brown stains on fixtures and laundry and tastes bitter and metallic. The EPA's aesthetic limit is 0.05 mg/L, with a health advisory at 0.3 mg/L over neurological effects, especially in infants.

Manganese greensand Filtration

A filter media coated with manganese dioxide that oxidizes dissolved iron and manganese on contact, then traps the particles. It is periodically recharged with potassium permanganate, and it needs a high enough pH (roughly 8 for manganese) to work well.

Maximum contaminant level (MCL) Standards

The highest amount of a contaminant the EPA allows in public drinking water. Private wells are not regulated, but MCLs are the benchmark to compare your own test results against.

Metered (demand-initiated) regeneration Equipment

A softener control that measures how much water you actually use and regenerates only when the resin is nearly spent, instead of on a fixed timer. It cuts salt and water waste, and it is the setup NSF/ANSI 44 requires before a softener can be rated for efficiency.

See also: Water softener , Salt efficiency , Brine

Micron Filtration

One millionth of a meter — the unit used to rate how fine a filter is. A 5-micron sediment filter traps particles down to 5 microns; the smaller the number, the finer the filter and the more it removes.

N

Nitrate Contaminant

A dissolved contaminant from fertilizer, septic systems, and animal waste. It is especially dangerous to infants. The EPA limit is 10 ppm, and it is removed by reverse osmosis or ion exchange, not by carbon filters.

NSF/ANSI standards Standards

Independent certifications that verify a filter does what it claims. Common ones: NSF 42 (taste and odor), 53 (health contaminants like lead), 44 (softeners), and 58 (reverse osmosis).

O

Oxidation Treatment

Adding oxygen (or another oxidizer like chlorine) to dissolved metals so they turn solid and can be filtered out. It is how most systems pull iron, manganese, and sulfur out of well water.

P

Parts per million (ppm) Units

How much of a substance is dissolved in water, by weight. One ppm is one milligram per liter (mg/L) — the two units are equal in water. Contaminant limits are usually written in ppm.

pH Water chemistry

A 0–14 scale of how acidic or alkaline water is; 7 is neutral. Acidic well water (low pH) corrodes pipes and can leach copper and lead, so it is often neutralized before other treatment.

R

Reverse osmosis (RO) Equipment

A filtration method that pushes water through a membrane so fine it blocks dissolved contaminants — arsenic, nitrate, TDS, and more. Usually installed under one sink for drinking water; it wastes some water as brine.

S

Salt efficiency Standards

How many grains of hardness a softener removes for each pound of salt it burns. NSF/ANSI 44 labels a unit 'efficiency rated' only if it removes at least 3,350 grains per pound of salt (California requires 4,000) and uses no more than 5 gallons of water per 1,000 grains removed.

Salt-free conditioner (TAC) Equipment

A no-salt alternative that does not remove hardness but changes the minerals into crystals that stick to surfaces less. It cuts scale without brine or sodium, but water stays technically hard.

See also: Water softener , Hardness , Scale

Scale Water chemistry

The hard, chalky mineral crust hard water leaves on faucets, kettles, and inside pipes and water heaters. Over time it clogs plumbing and shortens appliance life.

Sediment Water chemistry

Loose solid particles floating in water — sand, silt, clay, and rust flakes. Sediment makes water look cloudy, clogs downstream filters, and wears out appliances if it is not removed first.

T

Tannins Contaminant

Natural organic compounds (humic and fulvic acids) that leach from decaying leaves, bark, and peat into shallow groundwater, staining well water yellow to tea-brown. They are an aesthetic problem, not a health risk, and are removed by a tannin-selective anion exchange resin.

Total dissolved solids (TDS) Water chemistry

The combined weight of everything dissolved in your water — minerals, salts, and metals — measured in ppm. High TDS can make water taste metallic or salty, but the number alone does not tell you which contaminants are present.

U

Upflow regeneration (brining) Treatment

A regeneration design where brine flows up through the bottom of the resin bed, hitting the most-depleted resin first, so it recharges more evenly and wastes less salt than older downflow units that send brine down from the top. Proportional brining goes further, drawing only as much salt as the measured exhaustion needs.

UV disinfection Treatment

An ultraviolet lamp that kills bacteria and viruses as water flows past it, with no chemicals. It handles coliform and E. coli but only works on clear water, so it goes last, after sediment and iron are removed.

W

Water softener Equipment

A system that removes hardness by swapping calcium and magnesium for sodium in a resin bed — a process called ion exchange. It stops scale but adds a small amount of sodium and needs salt refills.

Well water test Testing

A lab or at-home analysis that tells you exactly what is in your water. Because private wells are unregulated, a test is the starting point for every treatment decision — you treat what the report shows, not what you guess.

Whole-house filter (point of entry) Equipment

A system installed where the water line enters the house (point of entry, or POE), so every tap, shower, and appliance gets treated water — as opposed to a point-of-use filter that treats just one fixture.