⚡ Water Electrical Conductivity

Physicochemistry PN-EN 27888

Overview

STATUS (as of 28.10.2026). PN-EN 27888:1999 — Polish version, published 27.05.1999, implements EN 27888:1993 [IDT] and ISO 7888:1985 [IDT]; it replaced PN-C-04542:1977. The standard is current — no withdrawal note.

SCOPE (clause 1). The standard specifies a method for measuring the electrical conductivity of all types of water. Conductivity is used to monitor the quality of surface waters, process waters in water supply and treatment plants, and waste waters; it also makes it possible to check the completeness of an analysis of ionic constituents. Sometimes absolute values are important, sometimes only relative changes.

TERMS (clauses 2–3). Electrical conductivity (γ) is the reciprocal of the resistance, measured under specified conditions, between the opposite faces of a unit cube of an aqueous solution; it is expressed in S/m (1 S/m = 10⁴ µS/cm = 10³ mS/m). It is a measure of the current conducted by the ions and depends on their concentration and nature, on the temperature and on the viscosity of the solution. Even pure water has a small conductivity as a result of its own dissociation.

TEMPERATURE (2.4, 7.2). Results are compared after conversion to the reference temperature of 25.0 °C. Measurement at 25.0 ± 0.1 °C is the most accurate; a measurement at another temperature is corrected with the instrument's temperature compensator (calibrated strictly according to the manufacturer), with the temperature coefficient of the sample — γ25 = γθ / [1 + (α/100)(θ − 25)] — or with the f25 factors of Table 3; each of these corrections gives a less accurate result than a measurement at 25.0 °C. The factors of Table 3 apply to natural waters with a γ25 of about 6–100 mS/m and are not applicable to potassium chloride solutions — therefore calibration is always carried out at 25.0 ± 0.1 °C. Earlier results quoted as γ20 can be converted to 25 °C for such waters with the factor 1.116.

INTERFERENCES (clause 9). The result is affected by contamination of the sample in the cell; suspended matter, grease and oil can foul the electrodes and change the cell constant, which can only be detected by checking with a potassium chloride standard solution. Air bubbles collecting on the electrodes when the sample is warmed to 25 °C interfere with the measurement. Conductivities below 1 mS/m are influenced by carbon dioxide and ammonia from the air — such waters are measured in a flow-type cell; for water of very low ion content the contribution of the conductivity of the water itself may be significant.

DRINKING WATER — LEGAL REQUIREMENTS. Regulation of the Minister of Health of 22 May 2026 (Journal of Laws 2026, item 748): electrical conductivity 2500 µS/cm (250 mS/m), determined at 25 °C; the water should not be corrosive (Annex 1 Part C Table 2 item 8). Conductivity is one of the group A monitoring parameters (Annex 3); measurement uncertainty — 20 % of the parametric value (Annex 4 Part B).

WATER MONITORING — LEGAL REQUIREMENTS. Regulation of the Minister of Infrastructure of 13 July 2021 (Journal of Laws 2021, item 1576), Annex 8, indicator 3.3.2: in the monitoring of surface water bodies and groundwater bodies, the reference methodology for the indicator “specific electrolytic conductivity at 20 °C” (electrometric, conductometric method) is PN-EN 27888 or a test procedure; another methodology may be used once its equivalence with the reference methodology has been demonstrated (explanatory note 1).

WHAT WE DO NOT GIVE HERE. The values of Table 2 of the standard (recommended cell constants for the measuring ranges) and the standard deviations of Tables 4 and 5 (measurements by one laboratory in the United Kingdom). Repeatability depends on the instrument — the standard refers to the manufacturer's data (8.2).

Method principle

Direct measurement of the electrical conductivity of an aqueous solution with a suitable instrument. Conductivity is a measure of the current conducted by the ions present in the water and depends on the concentration of the ions, their nature, the temperature and the viscosity of the solution.

The electrical conductivity is obtained by multiplying the measured conductance by the cell constant K = l/A (m⁻¹), which results from the geometry of the cell and is determined empirically with potassium chloride standard solutions. Many instruments have a built-in cell constant correction and display the electrical conductivity directly.

Applications

• Water intended for human consumption — electrical conductivity 2500 µS/cm, determined at 25 °C (Journal of Laws 2026, item 748, Annex 1 Part C); a group A monitoring parameter (Annex 3)
• Monitoring the quality of surface waters (clause 1)
• Process waters in water supply and treatment plants (clause 1)
• Waste waters (clause 1)
• Checking the completeness of an analysis of the ionic constituents of water (clause 1)

Key parameters

Standard

Standard number

PN-EN 27888:1999

Title (PL)

Jakość wody — Oznaczanie przewodności elektrycznej właściwej

Title (EN)

Water quality — Determination of electrical conductivity

Step-by-step procedure

1. Sampling

   Into a polyethylene bottle, completely filled and tightly stoppered; not into soda glass bottles. The measurement is made as soon as practicable, particularly when gases (carbon dioxide, ammonia) may be exchanged with the air or biological activity is possible (clause 6).

2. Storage

   Biological activity is reduced by storing in the dark at 4 °C; before the measurement the sample is brought to equilibrium at 25 °C. No suitable preservative is known (clause 6).

3. Instrument and cell constant

   Prepare the instrument according to the manufacturer, with a cell of known cell constant appropriate to the range (Table 2). If the cell constant is not accurately known — determine it with potassium chloride standard solutions appropriate to the range; check the cell constant at least once every 6 months (7.1).

4. Measurement

   For high-precision work, measure when the sample and the parts of the apparatus in contact with it have reached 25.0 ± 0.1 °C — this eliminates errors from compensation and conversion. Instrument without cell constant correction: electrical conductivity = measured conductance × cell constant (7.1).

5. Temperature correction

   When measurement at 25.0 °C is not possible (e.g. in the field), measure at a known temperature θ and convert with the instrument's compensator, the temperature coefficient of the sample or the f25 factor of Table 3 for natural waters (7.2).

6. Result

   The result is read from the instrument and reported as γ25 in mS/m with reference to the standard; for a measurement at another temperature the measuring temperature and the method of correction are also reported, e.g. “γ25 = 25.8 mS/m (according to ISO 7888), measuring temperature 11.5 °C, mathematical correction” (clause 8).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• The standard gives no safety warnings; reagents, including the platinizing solution (4.5), are handled according to the safety data sheets

Frequently asked questions