Type I vs Type II Laboratory Water: International Standards, Water Quality and Selection Guide

Water purity plays an important role in laboratory testing, analytical accuracy, and scientific research. Impurities such as dissolved salts, organic compounds, particles, and microorganisms can affect experimental results and the performance of sensitive laboratory instruments.

For this reason, laboratories use different water grades depending on their analytical procedures and required water quality.

Type I and Type II are two commonly specified laboratory reagent water categories. Understanding their technical specifications, purification technologies, and applications is essential when choosing a suitable laboratory water purification system.

This guide introduces international laboratory water standards, compares Type I and Type II water quality, explains DI and EDI purification technologies, and provides practical guidance for selecting laboratory water purification equipment.

1. International Standards for Laboratory Water Quality

Two important international specifications for laboratory water are ASTM D1193 and ISO 3696.

ASTM D1193 – Standard Specification for Reagent Water

ASTM D1193 is an established standard for laboratory reagent water.

The current edition, ASTM D1193-24, defines four water types:

• Type I

• Type II

• Type III

• Type IV

The specification also includes additional microbiological grades.

ASTM D1193 evaluates water quality using parameters such as electrical conductivity, resistivity, Total Organic Carbon (TOC), sodium, chloride, silica, and microbiological contamination.

Different purification technologies may be used, provided that the produced water meets the applicable specifications.

Importantly, the type designations should not be interpreted simply as a numerical ranking of overall water purity.

ISO 3696 – Water for Analytical Laboratory Use

ISO 3696:1987 classifies water for inorganic chemical analysis into three grades:

• Grade 1

• Grade 2

• Grade 3

The standard specifies requirements for laboratory water intended for different inorganic analytical procedures.

Its scope does not cover every application involving organic trace analysis, biological analysis, or medical testing.

ASTM Type I and ISO Grade 1 are not automatically equivalent classifications. Laboratories should follow the standard specified by their analytical method or quality management procedures.

2. Type I vs Type II Water: International Quality Specifications

Laboratory water quality should be evaluated using measurable parameters rather than purification technology alone.

The following table presents numerical reference limits published in the historical ASTM D1193-99e1 specification.

Source: ASTM D1193-99e1, historical edition. Values are provided for technical comparison and should not be presented as the verified limits of ASTM D1193-24. Laboratories must consult the applicable edition for compliance requirements.

What Do These Parameters Mean?

Resistivity

Resistivity measures how strongly water resists electrical current. It is generally used as an indicator of dissolved ionic contamination.

Higher resistivity usually indicates lower levels of dissolved ions.

Modern ultrapure water purification systems commonly produce water with a resistivity of approximately 18.2 MΩ·cm at 25°C, close to the theoretical limit for pure water.

Conductivity

Conductivity measures the ability of water to conduct electricity.

Lower conductivity usually indicates fewer dissolved ionic impurities.

At 25°C, a resistivity of 18.2 MΩ·cm corresponds to a conductivity of approximately 0.055 µS/cm.

Total Organic Carbon (TOC)

TOC indicates the concentration of carbon associated with organic compounds in water.

Low TOC levels are particularly important in sensitive chromatographic and other analytical applications.

Modern low-TOC ultrapure water systems may offer performance substantially better than the historical ASTM reference limits.

Sodium, Chloride and Silica

These are examples of inorganic contaminants that can interfere with analytical procedures or affect laboratory equipment.

Their acceptable concentrations depend on the relevant water specification and application.

Particles and Microorganisms

Particle and microbial contamination can affect sensitive analytical procedures and biological applications.

However, particle limits should not be assigned universally to Type I or Type II without reference to the applicable specification.

ASTM also addresses microbiological contamination through additional grades, rather than defining a single bacterial count for every water type.

For cell culture and other life science procedures, additional limits on endotoxins, microorganisms, or nucleases may be necessary.

3. What Is Type I Ultrapure Water?

Type I water is commonly described as ultrapure laboratory water.

It is frequently selected for sensitive analytical procedures where low ionic contamination and appropriate control of organic or biological impurities are important.

Modern Type I ultrapure water systems commonly provide:

• Resistivity approaching 18.2 MΩ·cm at 25°C

• Very low conductivity

• Low organic contamination when equipped with suitable purification technology

• Additional particle or microbiological control when required

The exact quality requirements depend on the analytical method and applicable standard.

Typical Applications of Type I Water

Type I ultrapure water is commonly used for:

• High-Performance Liquid Chromatography (HPLC)

• Ultra-Performance Liquid Chromatography (UPLC)

• Liquid Chromatography-Mass Spectrometry (LC-MS)

• Inductively Coupled Plasma Mass Spectrometry (ICP-MS)

• Ion chromatography

• Trace element analysis

• Sensitive sample and standard preparation

• Selected molecular biology procedures

For life science applications, suitable ultrafiltration or terminal filtration may be required to achieve additional contamination control.

4. What Is Type II Purified Water?

Type II water is a laboratory reagent water category used for applications where its specified purity is appropriate.

It can be produced through different purification processes, including distillation, reverse osmosis, ion exchange, or electrodeionization.

Some modern Type II water systems achieve much higher resistivity and lower conductivity than the minimum requirements published in historical ASTM specifications.

For example, the YUKEY Eminent EU series includes a DI water output with a manufacturer-specified resistivity above 16 MΩ·cm at 25°C.

This demonstrates that a water purification system's actual performance may exceed the minimum ionic purity expected for a particular water category.

Typical Applications of Type II Water

Depending on the required specifications, Type II water may be used for:

• Routine analytical procedures

• Laboratory reagent preparation

• Buffer and solution preparation

• Selected microbiological media preparation

• General chemical testing

• Glassware rinsing

• Feed water for ultrapure water purification systems

• Compatible laboratory instruments requiring purified water

Some procedures, particularly cell culture and sensitive biological testing, may require further treatment and verification of microbial or endotoxin levels.

5. DI vs EDI: Different Technologies for Laboratory Pure Water

Deionization and electrodeionization are commonly used in laboratory water purification systems.

Both can be incorporated into systems intended to produce Type II laboratory water.

Deionization (DI)

DI uses ion-exchange resins to remove positively and negatively charged ions from water.

As the resins become exhausted, they require replacement or regeneration according to the system design.

DI technology is widely used because of its effectiveness, flexibility, and suitability for laboratory water purification.

Electrodeionization (EDI)

EDI combines ion-exchange media, ion-selective membranes, and electrical current to remove dissolved ions continuously.

Electrical regeneration allows the ion-exchange media to remain active during normal operation, reducing the need for conventional chemical regeneration.

EDI is particularly suitable for systems designed for continuous purified water production.

DI vs EDI Comparison

Neither technology automatically guarantees compliance with a particular water quality specification. The finished water should be evaluated

 against all relevant parameters.

6. How to Choose the Right Laboratory Water Grade

Start with Your Analytical Application

Select water based on the laboratory method rather than assuming that one grade is suitable for every procedure.

Sensitive trace analysis may require ultrapure water with particularly low ionic and organic contamination.

Routine laboratory preparation may require an appropriate Type II water specification.

Evaluate Water Quality Parameters

Consider resistivity, conductivity, TOC, particles, microorganisms, and any application-specific contaminants.

Determine Daily Water Consumption

Estimate average daily use and peak demand.

A system should have adequate production capacity and storage to support laboratory operations.

Check Purification Technologies

Review whether the system includes RO, DI, EDI, UV, UF, or other purification stages.

Select the necessary configuration according to the required water quality.

Consider Storage and Dispensing

Storage tank materials, ventilation filters, remote dispensing arms, and automatic dispensing functions can affect convenience and contamination control.

Review Water Quality Monitoring

Online resistivity monitoring, consumable management, alarms, and data recording can improve system reliability and support laboratory quality management.

7. YUKEY Laboratory Water Purification Solutions

Shanghai Yukey Technology Co., Ltd. supplies laboratory water purification equipment for analytical laboratories, research institutions, biotechnology, and general laboratory applications.

The Smart and Eminent series offer different purified-water and ultrapure-water configurations.

Smart SD Series – Economical Type II Purified Water

The Smart SD series is designed for laboratories requiring Type II purified water using a DI-based purification configuration.

It offers a compact and practical solution for routine laboratory water requirements.

Smart SU Series – Type I Ultrapure Water

The Smart SU series is designed for Type I ultrapure water applications.

Selected configurations provide a nominal resistivity of 18.2 MΩ·cm at 25°C.

UV-equipped or UF-equipped configurations can be selected for applications requiring additional organic or biological contamination control.

Eminent ED Series – Intelligent Type II DI Water

The Eminent ED series is positioned for Type II laboratory purified-water production using DI technology.

The Eminent platform offers advanced touchscreen controls, water quality monitoring, and data management features, depending on the model.

Eminent EU Series – Integrated Type I and Type II Water

The Eminent EU series is designed to provide both ultrapure water and purified DI water.

Its two water outputs are positioned as:

Type I UP Water

Nominal resistivity of 18.2 MΩ·cm at 25°C.

Selected UV configurations have manufacturer-specified typical TOC values of 2 ppb under defined operating and feed-water conditions.

Type II DI Water

Manufacturer-specified resistivity above 16 MΩ·cm at 25°C, with conductivity below 0.063 µS/cm under specified conditions.

The EU series offers production capacities of 20, 40, and 60 L/h.

Selected configurations feature UV treatment, ultrafiltration, a 5-inch color touchscreen, remote dispensing options, and a standard 35 L PE storage tank.

Eminent EDE Series – Type II Water with EDI Technology

The Eminent EDE series incorporates electrodeionization technology for Type II purified-water production.

It is suitable for laboratories seeking continuous ionic purification and intelligent system management.

Eminent EUE Series – Type I Ultrapure Water and Type II EDI Water

The Eminent EUE series combines EDI purification with an ultrapure water polishing stage.

It is positioned to provide both Type II purified water and Type I ultrapure water for laboratories with different water requirements.

YUKEY Product Selection Guide

The above water-grade descriptions reflect the manufacturer's product positioning. Compliance with a particular edition of ASTM D1193, ISO 3696, or other technical specifications should be confirmed using complete model-specific water quality data.

8. Laboratory Water Quality Monitoring and Maintenance

Consistent water quality requires regular monitoring and maintenance.

Recommended activities include:

• Monitoring resistivity and conductivity

• Checking TOC when required

• Replacing exhausted purification cartridges

• Inspecting RO membrane performance

• Maintaining water storage tanks

• Replacing terminal filters

• Sanitizing the system as instructed

• Performing periodic water quality verification

Critical analytical applications should follow established laboratory quality assurance procedures.

9. Conclusion

Selecting between Type I and Type II laboratory water requires an understanding of both international specifications and the needs of the intended application.

Type I ultrapure water is commonly selected for sensitive analytical procedures, while Type II purified water is used for a range of laboratory applications according to its specified quality.

DI and EDI are two different technologies that can both be used to produce high-purity laboratory water.

YUKEY offers Smart SD, Smart SU, Eminent ED, EU, EDE, and EUE purification systems to support different water quality, production capacity, and operating requirements.

Need Help Choosing a Laboratory Water Purification System?

Shanghai Yukey Technology Co., Ltd. provides laboratory pure water and ultrapure water purification solutions for customers worldwide.

Contact our team with your required water quality standard, laboratory applications, daily water consumption, and feed-water conditions. We can help you select a suitable purification system and provide model-specific technical specifications.