Pure Water – What is ASTM Type II Water?

Have you ever thought about the significant role that water plays in a laboratory?  Every lab is different and has unique needs based on tests, experiments, applications and processes being conducted. Based on the functions of the lab, there may be a need for just one type of water or multiple types.  ASTM International (formerly known as American Society for Testing and Materials) defines laboratory grade water into four categories: Type I, II, III and IV. Almost every lab is going to need Type II Water, which some refer to it as pure water.

Type II water will have a resistivity of ≥1 MΩ-cm at 25°C and TOC (total organic carbons) of <50 ppb. Type II water is needed for basic lab functions and thats why almost every lab needs it!

RESISTIVITY is measured in Ohms and indicates the ability of water to either resist or conduct an electrical current.  The resistivity measurement is correlated to the amount salt (ionic material) that is dissolved in the water.  A higher resistivity means that the salt concentration is low.  On the flip side, water with a higher concentration of salt would have a lower resistivity.

Image listing the types of lab applications that type II water can be used for

There are two types of purification processes  to achieve Type II, pure water – distillation and deionization. Distillation is known to remove a wider range of impurities than any other purification process.  However, its a time consuming process.  For labs that need Type II, pure water on demand, deionization may be a better fit.  In this purification process, water is pushed through ion-exchange resins that can remove impurities such as mineral ions.  

For labs that are in search of an economical, simple to use on demand type II water system, LabStrong™ recommends the Cascade™ Type II Water Purification System.  The Cascade™ is designed with the user in mind and allows lab personnel to operate and perform regular maintenance simply and efficiently. The system will produce up to 2L/minute of ASTM Type II water with a resistivity of up to 15 meg Ω/cm.

  • Simple installation requiring no electricity and a simple water connection to a tap or pretreat source.
  • Quickly connect and disconnect cartridges for installation and replacement.
  • Easy to read pressure gauge, with a pressure regulator to control inlet water pressure.
  • Shut off/control valve allows users to easily control water output.


Available in a Dual or Quad option, various cartridge kits are available that feature a color-changing resin. The color-changing resin helps to indicate when it’s time to replace exhausted cartridges to ensure consistent water quality.  Our Technical Service team can assist you in selecting the best cartridge kit based on your labs source water and uses of the product water. Contact us at 563-588-8900 or via email at technicalservice@labstrong.com.

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