Know Your Pure Water For Lab Experiments

All laboratory work depends on pure water. The experiments can be medium-based or thermal-based. All these require pure water to carry out the further processes. As a laboratory fellow, you must be aware of the importance of pure water giving out accurate results when processed upon. 

For smooth processing of various lab experiments, pure water is needed in accurate amounts and with zero impurity level.  All lab experiments are sensitive and are carried out with utmost sincerity with the help of a water purification system laboratory.  Here, pure water plays a major role in giving out accurate, effective, and good results. Every lab worker should know how to get the pure water and test it accordingly before approaching the exact lab experiment. 

For testing of pure water for lab works, the American Society for Testing and Materials(ASTM), has defined some standards that encompass various pure water types.  According to the ASTM, lab water is categorized into four main types: 

  • Type I 
  • Type II 
  • Type III
  • Type IV

Though the standards are set by ASTM, other standards like ISO and CLSI-CLRW  are also there to testify to the ultrapure water system for the laboratory. Before going further, let’s look at the properties that define the purity of water in a water purification system for a laboratory. 

Water Purity Definitions

According to the standards of ASTM, several factors define the water purity in the water purification system for laboratories. These standards are well marked by the scientists for their versatility and accuracy. Let’s have a look at them in brief: 


Conductivity is defined as the conductance of electricity with ease through the water.  Perfect pure water should have a low level of conductance. In this sense, type III and type IV pure water is tested.  More conductance means more ions in the water which can conduct electricity. So, it is advised to measure the conductivity of pure water before approaching any laboratory water purifier. 


The term resistivity measures the resistance or hindrance caused by the ions of water while conducting electricity. This factor is typically high in type I and Type II pure water types. It is said that the more resistivity, the less is the ionic content and hence, makes the pure water more desirable for lab work. The water purification system for laboratory use also uses ohm-cm; this feature produces type I and type II water. 

TOC – Total Organic Content

This term is designated for the total organic content present in the water. While carbon testing, the TOC is measured. The measured value provides accurate measurement for the purity of water. This measurement also accounts for the presence of microorganisms with organic content in any laboratory water purifier. 


Turbidity is defined as water clarity. In some of the water purification systems for laboratory use, have the turbidity index. This turbidity level gives a rough idea about the water purity along with the contaminants and other materials present in it.  The turbidity check is advised for the low pure water like type III and Type IV. 

Hence, the above four factors determine the purity of lab water or pure water. It is advisable to check the purity first and then commence any experiment. This way, the accuracy of the experiment does not get affected and perfect results are obtained through the use of a laboratory water purifier. 

Different types of Pure water in the lab

Now after reading the preceding section about the definition of pure water and its factors. Let’s understand the different types of pure water in detail. The ASTM standards have defined each type with great understanding and their effects on the applications.  

Type I: Ultrapure Water

The first and the purest water is ultrapure water.  It is designated as Type I by the ASTM standards. Among the four types of pure water, ultrapure water is the most desired water used in the laboratory. Many laboratory water purification systems have this feature of obtaining type I water easily. You can easily check the laboratory water purification system price over the internet. 

The properties of ultrapure water are as follows: 

  • Total organic content:  Less than ppb 
  • Resistivity:  Greater than 18 M-Ohm- cm 
  • Conductivity: Less than 0.056 muS/cm 

For the water to be type I, it should execute all the above properties.  Ultrapure water finds its use in multiple lab experiments, both small scale and large scale.  These applications are : 

Water purification system laboratory is used commonly for the purification of ultrapure water. In type I water, the bacteria, and organic content levels are maintained lowly.  The ultrapure water system for the laboratory helps in this manner.  

Type II: General Grade Laboratory water

This type of water is not considered ultrapure but is still pure to be used in lab experiments.  The type II water is called general grade laboratory water normally. Type II water is produced by the combination of reverse osmosis and some ion exchange technology.  Any ultrapure water system for laboratories can also produce type II water. Deionisation eliminates most of the ions from this type of water making it ideal for lab experiments. 

Type II water has the following properties

  • Total organic content:  Minimum 50ppb 
  • Resistivity: Greater than the 1M-ohm-cm 
  • Conductivity: Less than 1 mu-S/cm 

Type II water has equal importance as type I water. It has the following application in the laboratory: 

Type II water can also be produced through a water purification system for laboratory use.  

Type III: RO water

The term RO is familiar to all of us. It is the abbreviation of Reverse osmosisLab water purification systems include this type of water purification for lab work. Many other wet-lab works are also carried throughout the type III pure water.  

Following are the properties of Type III pure water: 

  • Total organic content: Less than 200ppb 
  • Resistivity: Greater than 4 M-ohm-cm 
  • Conductivity: Less than 0.25 mu-S/cm 

All kinds of secondary work in the laboratory is done through type III pure water. The following are the applications of reverse osmosis water or type III : 

  • General use in laboratory 
  • Used in the initial phase of type I and type II pure water 
  • For rinsing and secondary laboratory tasks 

The RO water is produced by tap water through the reverse osmosis process. Type III water has a low level of contaminants which makes it more desirable for lab works. 

Type IV:& Feedwater

The last type of pure water is the feed water which is normally called distilled water. This type of pure water is produced through a laboratory water purifier for experimental works.  

Following are the properties of it: 

  • Total organic content: No such standard till now 
  • Conductivity: Less than 5 muS/cm 
  • Resistivity : 200 K-ohm-cm 

Type IV  has less importance than the above three types of pure water.  This type of water is used in various types of small-scale lab experiments as well as helpful in producing pure water of types I and II. Type IV pure water is produced through the reverse osmosis of tap water. Lab water purification systems are all prevalent in the market to get this type of pure water. 


The pure water standards are complex and need good analysis for approaching any lab experiments. All standards are critical to the factors of determination of pure water as well as the type of pure water. A lab water purification system is present which produces pure water for executing all experiments of the laboratory.

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