What Is the Normal Standard for the Odor and Taste of Drinking Water?

Odor and taste are among the most immediate sensory indicators of drinking water quality. Unlike chemical parameters that can be expressed as numerical concentrations, the standard for odor and taste is fundamentally qualitative—yet it carries clear regulatory weight and scientific underpinning.

The Regulatory Standard

Under China's current Standards for Drinking Water Quality (GB 5749-2022), the mandatory requirement for odor and taste is simply stated as "no abnormal odor or taste" . This means that drinking water should not exhibit any unpleasant or unusual smell or flavor detectable by human senses. In routine water quality monitoring reports, this parameter is typically recorded as "none" or "Grade 0" to indicate compliance .

The standard is applied through sensory evaluation, specifically the sniff-and-taste method specified in GB/T 5750.4-2023 (Section 6.1) . Trailed panelists assess water samples under controlled conditions to determine whether any off-odor or off-taste is perceptible.

International Approaches

The World Health Organization similarly addresses odor and taste under "acceptability aspects" of drinking water quality, recommending that water should be "non-objectionable" or "acceptable" to consumers . The U.S. Environmental Protection Agency (EPA) has established Secondary Maximum Contaminant Levels (SMCLs) as non-enforceable guidelines for aesthetic effects, including taste and odor, to help maintain consumer confidence in tap water . These secondary standards typically include a threshold odor number (TON) of 3 .

The Science Behind Off-Odors

While the standard itself is qualitative, its scientific basis involves specific chemical compounds with extremely low detection thresholds. The most notorious are 2-methylisoborneol (2-MIB) and geosmin—microbial metabolites produced by algae and actinobacteria. 

These compounds can cause musty, earthy, or muddy odors even at concentrations as low as 4 to 10 nanograms per liter . To address this, the latest Chinese standard (GB 5749-2022) has incorporated both 2-MIB and geosmin as extended indicators, setting a limit of 10 ng/L for each .