MRDL in Drinking Water: Chlorine and Chloramine Limits (4 mg/L)

An MRDL works like an MCL, but for the disinfectants your utility adds on purpose. Contaminants get a maximum contaminant level; chlorine, chloramines and chlorine dioxide get a maximum residual disinfectant level instead.

What’s the difference between an MRDL and an MRDLG?

The federal rules for water quality reports (40 CFR 141.153) define both:

• MRDL: “The highest level of a disinfectant allowed in drinking water. There is convincing evidence that addition of a disinfectant is necessary for control of microbial contaminants.” It’s the enforceable limit, set in 40 CFR 141.65.
• MRDLG: “The level of a drinking water disinfectant below which there is no known or expected risk to health.” The same definition adds that MRDLGs “do not reflect the benefits of the use of disinfectants to control microbial contaminants.” The goals are in 40 CFR 141.54.

As of October 20, 2026, the MRDL for chlorine and for chloramines is 4.0 mg/L (as Cl2), and for chlorine dioxide 0.8 mg/L (as ClO2). Each goal is the same number.

Where do I see it in my water report?

The report’s section on detected contaminants covers those subject to an MRDL, and a report with that data must print these definitions. The disinfectant your utility uses usually appears in the results table next to its MRDL and MRDLG. Our guide to reading your water quality report explains each column, and chlorine vs chloramine covers what the two common disinfectants mean for taste and filters.