What Is a Reasonable Range for Water Conductivity?

Conductivity measures a water body's ability to conduct electrical current, which directly reflects the total concentration of dissolved ions—calcium, magnesium, sodium, chloride, sulfate, and others. Unlike pH or temperature, conductivity does not have a single universal "normal" value. Its reasonable range depends entirely on the water's intended use, its source, and the regulatory framework that applies. Understanding these context-dependent benchmarks is essential for proper water quality assessment.

Drinking Water

China's current Standards for Drinking Water Quality (GB 5749-2022) does not set a direct limit for conductivity. Instead, it regulates total dissolved solids (TDS) at no more than 1000 mg/L. Since conductivity and TDS have an empirical relationship—TDS (mg/L) roughly equals 0.64 times conductivity (μS/cm)—this implies an upper conductivity limit of approximately 1500 μS/cm for tap water meeting national standards.

In practice, most water utilities maintain much tighter internal controls. Finished water from treatment plants typically ranges from 200 to 800 μS/cm, with well-managed systems sustaining 150 to 400 μS/cm. Regional differences are notable: surface-water sources in southern China generally yield 100 to 400 μS/cm, while groundwater-dependent northern cities often see 400 to 800 μS/cm. The World Health Organization suggests an ideal drinking water conductivity of 50 to 500 μS/cm.

For bottled purified water, a separate product standard (GB 17324) mandates conductivity no higher than 10 μS/cm. Natural mineral waters, by contrast, contain higher mineral content and typically range from 100 to 1200 μS/cm, with common values falling between 300 and 800 μS/cm.

Surface Water

China's Surface Water Environmental Quality Standard (GB 3838-2002) does not list conductivity as a mandatory indicator. Nevertheless, empirical ranges have been established through long-term monitoring across different water quality classes. High-quality Class I and II waters—source water and nature reserves—generally exhibit conductivity between 50 and 300 μS/cm. 

Class III waters, which serve as secondary drinking water source protection zones, typically fall in the 200 to 500 μS/cm range. When conductivity rises to 500 to 800 μS/cm, it often signals the influx of diffuse or domestic pollution, commonly seen in Class IV to V river sections. Values exceeding 1000 μS/cm are frequently found in inferior Class V waters or in lakes and rivers affected by industrial discharge or high-mineralization geology.

Alternative references based on GB 3838-2002 specify upper limits by class: Class I ≤ 1000 μS/cm, Class II ≤ 2000 μS/cm, Class III ≤ 3000 μS/cm, Class IV ≤ 4000 μS/cm, and Class V ≤ 5000 μS/cm.

Industrial Water and Pure Water

Industrial applications impose widely varying requirements. In recirculating cooling water systems, conductivity is generally kept at or below 3000 to 4000 μS/cm. Reverse osmosis feed water typically requires conductivity no higher than 500 μS/cm.