Water quality standards

For various fields of use and requirements.

International Organization for Standardization (ISO)

ISO 3696:1987 distinguishes between three degrees of purity for water for analytical purposes in laboratories.

ParameterGrade 1Grade 2Grade 3
pH value at 25°C 5.0 up to 7.0
Conductivity at 25 °C [µS/cm]
Oxidizable matter, oxygen content [mg/l, max.]0.080.4
Absorption at 254 nm and a lenght of 1 cm (absorption units, max.) 0.0010.01
Residue after evaporation by heating to 110 °C (mg/kg, max.) 12
Silicon content [mg/l, max.]0.010.02

Clinical Laboratory Standards Institute (CLSI)

This institute defined the quality requirements of water for clinical laboratories. The regulations that were valid up to 2006 (NCCL types 1, 2 and 3) but were then invalidated by the requirement that water must be suitable for the intended usage. Only the degree of purity of so-called “Clinical laboratory reagent water” (CLRW) is described.

Resistance [MΩ x cm]10
TOC [ppb]< 500
Bacteria [CFU/ml]< 10
Particle ContentInline 0.2 µm-filter

American Society for Testing and Materials (ASTM)

The ASTM D1193-06 (2011) deals with the requirements for chemical analyses and physical tests.


Explore stakpure in 3D



OMNIA Produktvideo

Brochure pure and ultrapure water systems

Omnia Broschüre

Brochure Omnia xstouch Blueline

Omnia Broschüre

Brochure Omnia xsbasic

Omnia Broschüre