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Chlorine in drinking water

Also called Free chlorine, Residual chlorine, Chlorine (as Cl2).

Legal limit
4.0 ppm
Health goal
4.0 ppm

Values in parts per million (ppm). Forms or is added in treatment.

Where the rules stand

EPA sets a maximum residual disinfectant level (MRDL) of 4.0 ppm (4.0 mg/L as Cl2) and a goal (MRDLG) of 4 ppm. These are the disinfectant versions of an MCL and MCLG, and this data stores them in those fields.

The scale every TapBuff report uses for this contaminant: the legal line at the middle, twice it at the right.

What EPA says about health

EPA lists eye and nose irritation and stomach discomfort above the MRDL.

Where it comes from

Utilities add chlorine to control microbes, so it comes from treatment, not from the source water.

What handles it

  • NSF/ANSI 42

    Claim to look for: Chlorine Reduction

    Aesthetic claim for taste and odor. WQA wording: "Aesthetic Chlorine."

  • NSF/ANSI 177

    Claim to look for: Free Available Chlorine Reduction

    Shower filters only. WQA wording: "Free Available Chlorine."

Filters with that claim on a certifier’s listing

  • Brita Tahoe Pitcher with Elite Filter (OB60, OB06)

    Pitcher

    • WQA listing: 42, 53, 401 · checked Oct. 4, 2026
    Maker’s page

  • Brita Tahoe Pitcher with Original Filter (OB60, OB03)

    Pitcher

    • WQA listing: 42, 53 · checked Oct. 4, 2026
    Maker’s page

  • PUR PLUS 11-Cup Pitcher (PPT111W)

    Pitcher

    • NSF listing: 42, 53, 401 · checked Oct. 4, 2026
    • WQA listing: 42, 53, 401 · checked Oct. 4, 2026
    • IAPMO listing: 42, 53, 401 · checked Oct. 4, 2026
    Maker’s page

  • ZeroWater 10 Cup Pitcher (ZP-010)

    Pitcher

    • IAPMO listing: 42, 53 · checked Oct. 4, 2026
    Maker’s page

  • Clearly Filtered Filtered Water Pitcher

    Pitcher

    • NSF listing: 42 · checked Oct. 4, 2026
    • WQA listing: 42 · checked Oct. 4, 2026
    Maker’s page

  • PUR PLUS Faucet Filtration System, Horizontal (PFM400H)

    Faucet mount

    • NSF listing: 42, 53, 401 · checked Oct. 4, 2026
    • WQA listing: 42, 53, 401 · checked Oct. 4, 2026
    • IAPMO listing: 42, 53, 401 · checked Oct. 4, 2026
    Maker’s page

  • Brita Elite Water Filter Faucet System (SAFF-100/FF-100)

    Faucet mount

    • WQA listing: 42, 53, 401 · checked Oct. 4, 2026
    Maker’s page

  • Aquasana Claryum Direct Connect (AQ-MF-1)

    Under-sink carbon

    • IAPMO listing: 42, 53, 401 · checked Oct. 4, 2026
    Maker’s page

  • Multipure Aquaversa (MP750)

    Under-sink carbon

    • NSF listing: 42, 53, 401 · checked Oct. 4, 2026
    Maker’s page

  • LARQ Under Sink Water Filter

    Under-sink carbon

    • NSF listing: 42, 53 · checked Oct. 4, 2026
    Maker’s page

  • Waterdrop G3P600

    Under-sink reverse osmosis

    • IAPMO listing: 42, 53, 58 · checked Oct. 4, 2026
    Maker’s page

  • AquaTru Classic (AT2000)

    Countertop reverse osmosis

    • IAPMO listing: 42, 53, 58, 401 · checked Oct. 4, 2026
    Maker’s page

  • Aqua-Pure AP903

    Whole house

    • NSF listing: 42 · checked Oct. 4, 2026
    Maker’s page

Sources

  1. National Primary Drinking Water Regulations, U.S. EPA. Checked Oct. 4, 2026.
  2. NSF/ANSI 42, 53 and 401: Filtration Systems Standards, NSF. Checked Oct. 4, 2026.
  3. NSF Standards for Water Treatment Systems, NSF. Checked Oct. 4, 2026.
  4. Search for NSF Certified Drinking Water Treatment Units (standards and reduction claims lists), NSF. Checked Oct. 4, 2026.
  5. Find WQA Certified Products (Gold Seal listings by standard and claim), Water Quality Association. Checked Oct. 4, 2026.
  6. SDWA Dataset Download Summary (codes from SDWA_REF_CODE_VALUES.csv, 2026 Q2 extract), U.S. EPA ECHO. Checked Oct. 4, 2026.