What is the resistivity of pure water

Resistance & spec. resistance


Conductivity of liquids

The electrical conductivity of water depends, among other things, on how many ions and what type of ions are dissolved in the water. For example, the introduction of salts into the water and the resulting formation of ions lead to an increase in conductivity. In addition, the temperature of the water also plays a role (the electrical conductivity increases with increasing temperature).

In the case of bodies of water, the electrical conductivity provides initial indications of the inflow of rainwater and wastewater. High conductivity values ​​can be attributed, for example, to the runoff of paved business and farm areas after rainfall in the catchment area and peak values ​​in winter to the use of road salt in winter service.

With the help of electrical conductivity, the total content of dissolved salts in a body of water can be estimated relatively quickly. The salts can be of natural origin (e.g. weathering of rocks) or of human origin (e.g. road salt, industrial waste water).

One can roughly assume that with an electrical conductivity of \ (1000 \, \ rm {\ frac {\ mu S} {cm}} \) about \ (1000 \, \ rm {\ frac {mg} {\ ell }} \) (ppm) salts are dissolved in the water.

  • The incandescent lamp does not light up with pure tap water;
  • When adding table salt and then stirring, the light bulb lights up

When checking the water quality of lakes and rivers, the electrical conductivity of the water is also checked with so-called conductivity meters:

Electrical conductivity (conductivity) of the water in Berlin's Müggelsee from July 20th to July 27th, 2007.

Institute for Freshwater Ecology and Inland Fisheries (IGB), Berlin