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Contaminant family guide

Disinfection Byproducts in Tap Water

Disinfection byproducts can form when disinfectants react with naturally occurring material in source water. Utilities monitor defined compounds and groups.

Check my local water

3 compound guides2 with a federal MCL3 treatment methods named

What are disinfection byproducts?

A family label, not a compound

These substances are created during the essential process of controlling microbes in drinking water. Formation depends on treatment chemistry, source-water conditions, and time in the distribution system.

Compliance may be based on a group total or a locational running annual average rather than one household sample. Read the analyte, statistic, period, and source together.

Sources named in the compound records
  • Chlorination of water with organic matter
  • Municipal disinfection
  • Chloramination
Published compound guides

Three disinfection byproducts with federal limits

Each has its own limit.

Identifier not publishedTotal trihalomethanes (TTHM)TrihalomethanesTTHMs are disinfection by-products that form when chlorine reacts with natural organic matter in water. They are the trade-off of effective disinfection.80 µg/LMCLRead compound evidence →Identifier not publishedHaloacetic acids (HAA5)Haloacetic acids (five)HAA5 is a group of five haloacetic acids: disinfection by-products that, like TTHMs, form when chlorine reacts with organic matter.60 µg/LMCLRead compound evidence →Identifier not publishedChlorineFree chlorine / chloramine residualChlorine is the disinfectant most utilities add to control bacteria and viruses as water travels through the pipes. A residual at your tap is a sign disinfection is working; some systems use chloramine for a longer-lasting residual.4 mg/LMRDLAs chlorine (Cl₂)Read compound evidence →
How to read a local result

Four checks before you act

  1. STEP 1Identify the named analyte

    A family name may contain compounds with different standards and health contexts.

  2. STEP 2Keep the measurement attached

    Read the value with its unit, qualifier, sampling period, reporting limit and source.

  3. STEP 3Compare only with the stated reference

    PurityMap does not turn unlike compound results into a family score or safety verdict.

  4. STEP 4Verify the treatment claim

    The product certification must name the compound or reduction claim.

Treatment capabilities in the published records

Three methods, each named by the compound guides

A technology name is only a starting point. Confirm the product’s certification names the compound before choosing equipment.

Treatment technologies
  • Activated carbon

    Named by 3 of 3 compound guides in this family.

    TTHMHAA5Cl₂
  • Reverse osmosis

    Named by 2 of 3 compound guides in this family.

    TTHMHAA5
  • Catalytic carbon (for chloramine)

    Named by 1 of 3 compound guides in this family.

    Cl₂
Related intelligenceAssembled from PurityMap’s governed contaminant records. How we analyze water data
All contaminantsFind my waterTreatment technologiesWater intelligence mapPurityMap methodology