Chlorine Residual
Chlorine residual is the disinfectant still in the water when it reaches customers, measured so a utility can show that disinfection is holding all the way through its distribution system. Most reports say which residual they measured — free chlorine or total chlorine — but some print only "chlorine" or "chlorine residual" and leave the species unstated. This page covers a residual reported that way, with neither species named. EPA's limit is the same for chlorine either way: a maximum residual disinfectant level of 4.0 mg/L, with a maximum residual disinfectant level goal of 4 mg/L.
EPA MRDLG
4 mg/L
The level in drinking water below which there is no known or expected risk to health. This is a goal, not an enforceable limit.
Health Effects
Eye/nose irritation; stomach discomfort
Source: EPA — National Primary Drinking Water Regulations (retrieved 2026-07-27)
Common Sources
- Water additive used to control microbes
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About the EPA MRDLG
The EPA MRDLG (maximum residual disinfectant level goal) is the level of a drinking water disinfectant below which there is no known or expected risk to health. It is a non-enforceable public health goal; the enforceable limit water systems must meet is the MRDL.
Contaminant Type
Chlorine Residual is classified as a Disinfectants contaminant.
Related Disinfectants Contaminants
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