Water Treatment Glossary: Terms Explained

Plain-English water terms

From gpg and TDS to resin, regeneration and NSF/ANSI 58, here is what the terms on your water report and equipment quote actually mean.

Call or Text 24/7Get A Free Estimate

How to Use This Glossary

Water reports, test results and equipment quotes come with a lot of jargon. This glossary explains the terms you are most likely to see in Southern Nevada in plain language, with links to deeper guides. For the big picture, start with our Las Vegas hard water guide.

Terms A to C

Activated carbon A porous filter media that adsorbs chlorine and many taste and odor compounds. LVVWD notes carbon filters do not remove hardness, minerals, sodium or fluoride (LVVWD). See whole house filters.
Alkalinity The water’s ability to neutralize acid, mostly from bicarbonate. LVVWD’s 2026 summary lists alkalinity (as HCO3) of 137 ppm (LVVWD).
Birm A granular filter media used to reduce dissolved iron and manganese by oxidizing them into particles the filter bed can trap.
Brine tank The tank that holds salt and water for a softener. The softener draws this salty brine to recharge its resin. Nebraska Extension advises periodic checking and cleaning (UNL).
Bypass valve A valve that routes water around a softener or filter, used during service or to send untreated water to a specific line.
Catalytic carbon Activated carbon that has been processed to boost its chemical reactivity, often chosen for chloramine or hydrogen sulfide reduction.
CCR (Consumer Confidence Report) The annual water quality report every community water system must deliver by July 1 (EPA). Find yours on our water quality reports page.
Chloramine Disinfectant compounds that contain chlorine and ammonia; monochloramine is the form used in drinking water (CDC).
Chlorine residual The disinfectant still present as water travels to your tap. LVVWD adds chlorine as water leaves treatment, and its 2026 summary lists an average free chlorine residual of 0.99 ppm (LVVWD). CDC considers levels up to 4 mg/L safe (CDC). Read about chlorine taste in Las Vegas tap water.

Terms D to I

Deionization (DI) A process that uses cation and anion resins to strip dissolved ions, producing very pure water for labs, car wash spot-free rinses and other commercial uses.
Grain capacity The total grains of hardness a softener can remove before it must recharge (NDSU Extension). Size yours with our water softener size calculator.
Grains per gallon (gpg) The hardness unit softeners use. One gpg equals 17.1 mg/L (UNL). Check your area with our hardness lookup.
Hardness The amount of dissolved calcium and magnesium in water (USGS). LVVWD reports 280 to 291 ppm, or 16 to 17 gpg, which it calls very hard (LVVWD).
Hydrogen sulfide (H2S) A gas that gives water a rotten-egg smell, often linked to sulfur bacteria. Odor only in hot water can come from the water heater’s anode rod (Penn State Extension). See iron and H2S filters.
Ion exchange The process a softener uses: resin swaps sodium or potassium for calcium and magnesium (NSF). Learn about Las Vegas water softeners.
Iron bacteria Microbes that feed on dissolved iron or manganese and leave slimy, rust-colored deposits; usually a nuisance rather than a health risk (Penn State Extension).

Terms K to O

KDF Short for Kinetic Degradation Fluxion, a copper-zinc granular media often paired with carbon to reduce chlorine.
mg/L Milligrams per liter, the unit most lab reports use. In drinking water it is equivalent to ppm.
NSF/ANSI 42 and 53 Filter certifications: 42 covers aesthetic impurities such as chlorine, taste and odor, while 53 covers a contaminant with a health effect (NSF).
NSF/ANSI 44, 55 and 58 Standards for cation exchange water softeners (44), ultraviolet systems (55) and reverse osmosis drinking water systems (58) (NSF).
Oxidation Converting dissolved iron, manganese or hydrogen sulfide into solid particles, using air, chlorine or a catalytic media, so a filter can remove them.

Terms P to R

Perchlorate An industrial chemical once made at Henderson plants; EPA says contamination seeped into the Las Vegas Wash, Lake Mead and the Colorado River (EPA). LVVWD’s 2026 summary lists an average of 0.70 ppb (LVVWD).
Permeate The purified water that passes through a reverse osmosis membrane. See what is reverse osmosis.
pH A 0 to 14 scale of how acidic or basic water is. EPA’s secondary range is 6.5 to 8.5 (EPA), and LVVWD’s 2026 average is 7.8 (LVVWD). Read about the pH of RO water.
Point-of-entry (POE) Equipment installed where water enters the home so every tap gets treated water, such as a softener or whole-house filter.
Point-of-use (POU) Equipment that treats water at a single tap, such as an under-sink filter.
Post-filter A final carbon filter after the RO storage tank that polishes taste before water reaches the faucet.
ppm Parts per million; equal to mg/L in drinking water. Divide hardness in ppm by 17.1 to get gpg.
Prefilter Sediment and carbon cartridges ahead of an RO membrane that catch particles and chlorine to protect the membrane.
Regeneration The cycle in which a softener backwashes and flushes its resin with brine to restore its capacity (UNL).
Reject water Also called brine or concentrate: the stream an RO system sends to the drain, carrying the minerals the membrane held back.
Resin The bead bed inside a softener, usually sulfonated polystyrene beads charged with sodium (UNL).
RO membrane A semi-permeable sheet that reverse osmosis systems force water through under pressure (NSF). Compare reverse osmosis systems.

Terms S to Z

Salt bridge A hard crust of salt that forms in a brine tank and leaves a hollow space underneath, so the softener cannot make brine. It is a common sign your softener needs service.
Scale Hard mineral deposits left by calcium and magnesium on fixtures, pipes and heaters. See scale in pipes.
Secondary standards EPA’s non-mandatory guidelines for 15 contaminants that affect taste, color and odor, such as TDS and iron (EPA).
TAC (salt-free conditioning) Template-assisted crystallization converts hardness minerals into tiny crystals rather than removing them, so a hardness test still reads hard (UNL). Compare salt-free scale control.
TDS (total dissolved solids) Everything dissolved in water, minerals included. EPA’s secondary guideline is 500 mg/L (EPA); LVVWD’s 2026 average is 591 ppm (LVVWD).
UV disinfection Treatment that uses ultraviolet light to inactivate bacteria, viruses and cysts, certified under NSF/ANSI 55 (NSF).

Get Your Free Water Analysis

Not sure what is in your water or what equipment fits your home? Water Quality of Las Vegas offers a free water analysis and free estimates across the valley, from Henderson to Pahrump. Call or text 702-623-2724 any time, or request your free water analysis online.

Call 702-623-2724 Text Us 24/7 Request a Free Estimate