Pure Water: The Need Of Lab

Water is called the unsung hero of any lab experiments.  To execute all types of lab experiments, researchers and scientists need water. The water used here should be free of impurities. The impurity-free water is called pure water or lab water. All water purification systems for laboratories produce lab water in four different categories. These categories of water have different properties and purposes in a laboratory. A laboratory water purifier is installed in a laboratory to obtain pure water. In the water purification industry, the four types of water are famous for their properties and specific applications in the lab.

These applications of pure water vary from simple reactions to complex ones. For the biopharmaceutical industry, lab water plays an important role. There are more such types of applications of pure water popular in the laboratory. Most commonly, there are four types of pure water used in any type of laboratory.

The four types of water are as follows:

  • Type I – Ultrapure Water
  • Type II – General Laboratory Grade Water
  • Type III – Primary Grade Water
  • Type IV – Feed Water

All these types of pure water are obtained with the help of a water purification system for laboratory. The above-mentioned types of pure water are defined by a series of defined measurements of resistivity (M-ohm-cm), bacterial count(CFU/ml), total organic content (TOC) in parts per billion(ppb). These measurements are done to define the water as fit for the lab experiments. In other words, we can say that these measurements make the standards for defining a pure water type.

For larger experiments and research, pure water is required in ample amounts. In that case, a perfect water purification system is required. The water system should be capable of providing the type of pure water required for the experiment. Some water systems do produce type I as well as Type II water. Such systems are considered over other water systems. 

Now, let’s look into various types of pure water used in the laboratory along with their properties and areas of function.

Types of Lab Pure Water

All the above kinds of pure water are purified by a laboratory water purifier in ample amounts. If any researcher wants pure water, then he or she has to first install a lab water system in the laboratory. The market is full of such water purifiers. One can also check the water purification system for laboratory prices online with some subtle clicks on the internet.  Pure water is important for any kind of experiment being performed in a laboratory. 

1.  Type I – Ultrapure Water

The very first category of pure water is ultrapure water. This kind of water is the most favorable one in laboratory experiments.  It has a resistivity of 18.2 M-ohm-cm at the temperature of 25°, which is the need of all types of analytical experiments in the lab.

Some applications of ultrapure water:

Though ultrapure water is the purest form of any lab water, it also contains a negligible amount of impurities. These impurities can be organic contaminants, nucleases, endotoxins, etc.  However, they did not impact the resistivity of the type I water, but water purification systems for laboratory with good purification technologies are needed. 

In a lab water purification system, there is equipment that produces ultrapure water. The equipment is called a “polisher” that can be fed from a localized reverse osmosis system of a lab water system. In this area, the concentrations of bacteria, and other microbiological entities are maintained low through the help of dual-wavelength ultraviolet light. The UV light is maintained at a wavelength of 185nm and 254nm.  The water flows through a container containing this UV light. This damages the genetic molecules of the reproductive functions of the bacteria.  This ensures there are negligible bacteria present in the water. This damage further prevents the multiplication of the microbes in the water. Thus, type I water is produced after treating it with UV light in a water purification system for laboratory use.

In addition to the above system, the lab water system also has an Ultrafilter(UF) that can be used for the elimination of RNAse and DNAse from the water. The size exclusion technology is used here to eliminate such nucleases and it also helps in attracting various contaminants to itself.  This ensures the full removal of impurities from type I water so that it can be used for laboratory experiments.

2.  Type II – General Laboratory Grade Water

The second in the list is the general laboratory-grade water which is called type II pure water.  This type of water is produced by a combination of two water purification technologies. One is reverse osmosis and ion exchange or electrodeionization( EDI). Such combined technologies are found in water purification systems for laboratory.  The type II water has a resistivity of 1-15 M-ohm-cm that makes it fit for laboratory applications.

Some applications of general laboratory grade water are:

To produce the type II water, ion exchange is employed that removes ions from the RO water. The removal of ions is done by the resin beds. Water is overflowed over these ion exchange resin beds in a lab water purification system, which results in the removal of ions. The whole process is continued till all unwanted ions are replaced by hydrogen and hydroxyl ions. Thus, the type II water is obtained by the water distillation unit for the laboratory.

In the EDI technology, water is passed between anion and cation permeable membranes with the help of EDI cells.  The cell here contains some loosely packed resins that exchange unwanted ions with hydrogen ions.  The unwanted ions are attracted to the oppositely charged electrode which is flushed away before they reach there. In this way, the water is fully purified to become general laboratory grade water.

3.  Type III – Primary Grade Water

The third water type is called primary grade water. Type III water is produced through the combination of two technologies: carbon activation or filtration and reverse osmosis technology.  This combination is the most cost-effective method to remove the impurities from the water. Some water purification systems for laboratories use such combined technology to produce type II pure water.

The combined technology in a lab water system removes up to 99% of the water contaminants. In the RO system, the water is fed over the semipermeable membrane to a more concentrated solution with the help of external pressure. This pressure alters the osmotic pressure, which forces the water through the membrane, and hence, all impurities get deposited on the surface. The rest of the water flows down the surface.

RO technology uses the principle of diffusion which rejects a higher molecular weight impurity out of the water.  In some instances, the water which is fed into the lab water purification system has some impact on the RO technology.  The temperature of fed water, pressure, and physical condition, all affect the rate of purification. As type II water is made up of the combination of RO and exchange systems, it is also called RO water.

Some applications of primary grade water:

  • In Feeding Glassware Washing Machines
  • In Feeding Autoclaves
  • In Pre-treatment of Ultrapure Water Systems

4.  Type IV – Feed Water

The fourth type of water is called feed water or raw water or potable water. The quality of type IV water is dependent on its source. The feed water can be obtained from the underground strata, filtered by layers of various rocks and soil. But, the surface waters, like lake water or seawater, are always at a risk of environmental impurities. So, the feed water also requires certain filtration in the water distillation unit for laboratory.

The feed water is defined by measuring its following characteristics:

Type IV water has some common contaminants, like minerals, dissolved ions, organic compounds, and microorganisms.

Before using the feed water in the laboratory, it should be tested and pretreated in a lab water system.  This is done to ensure the quality of water for the lab applications. The pretreatment is necessary to avoid any damages in the downstream processing of purification technology. Common pre-filters used here are depth filters. These filters process the raw water by winding fibers that trap or attract impurities and thus, help in cleaning the raw water. A water softener can also be used for the purification of feed water. The water purification system for laboratory has such arrangements to process the raw material so that it can be used for lab applications.


The above-mentioned water types are crucial to any lab experiment. Every type of lab water has to go through various processes and filtration technologies to reach a standard purity level. The purity level of lab water is necessary for the execution of lab experiments.  The researcher should know what kind of water he or she wants for their laboratories. For this, they should be able to distinguish between all four types of lab water considerably.

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