Water value

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The water value describes different measurands in different scientific-technical fields.


The water value describes the chemical or electrochemical state of the water. Important water values ​​are the pH value , the degree of water hardness , the electrical conductivity and, in the case of seawater, the salt content or the resulting density of the water. Naturally occurring water contains a large number of dissolved substances that can affect water chemistry. This is particularly important for drinking and aquarium water.


In physics , the water value describes the heat capacity of a vessel. This can be determined by filling the vessel with water at a different temperature and, after the thermal equilibrium has been established, the temperature of the water is measured, which has then adjusted to that of the vessel. The term "water value" comes from this measuring method.

More precisely defined, the water value of a vessel is the amount of water that has the same heat capacity as the vessel.

Membrane technology

In membrane technology , the water value ( flux ) is a measure of the permeate capacity of a membrane and is specified in l / (m² · h) [= m / 1000 h = m / kh = meters per kilo hour = mm / h = millimeters per hour] . The permeability results from the flux and the (transmembrane) pressure difference and is given in l / (m² * h * bar) [= mm / barh]. In addition to the bursting pressure and the blow point, the water value is one of the simplest, but also the most reliable, ways to characterize the properties of a filter element.

See also: Permeation measurement


  • Munir Cheryan: Handbuch Ultrafiltration , B. Behr's Verlag GmbH & Co, Hamburg 1990, ISBN 3-925673-87-3