Deionized (DI) Water Systems: Design, Standards and Applications
Purified water design, production and validation solutions in full conformity with international pharmacopoeias and specific industry standards.
What Is DI (Deionized) Water?
DI (deionized) water is high-purity water from which all dissolved mineral content and ionic impurities have been removed. Conductivity (microsiemens/cm - µS/cm) or resistivity (megohm-cm - MΩ·cm) measurements are mainly used as quality indicators.
Depending on your process, deionization alone may not be enough; total organic carbon (TOC), microbiological load (CFU/mL) and endotoxin levels may also need to be kept under tight control. To achieve this, the right purification steps must be selected and integrated.
System Installation Flow
For optimum production and safe distribution of DI water systems, we apply staged purification and loop design principles.
1. Production Line (Make-up)
- Pre-conditioning: Raw water that has passed through sand filter, activated carbon and softening units is freed of particles by passing through cartridge filters rated 5 micron and then 1 micron in series.
- Bioburden control: Before the Reverse Osmosis (RO) system, the water is passed through a 254 nm UV disinfection system to eliminate microbiological risks.
- Purification: The water is deionized by passing through the RO system (double-pass RO or CEDI-supported if required).
- Online control: Water quality is continuously verified before storage with online conductivity and pH analyzers.
2. Storage and Distribution (Loop) Line
- Deionized water is collected in a 316L or special-grade tank sized to the usage needs and pumped into the circulation (loop) line.
- Point-of-use protection: On the loop line, before it reaches the production points, the water is passed through a UV system again (254 nm, or 185 nm for TOC reduction) and a 0.2 micron membrane filter.
- Design: AISI 316L stainless steel is used in the line (polymers such as PVC, PP and PTFE can also be selected depending on the application). The line is equipped with aseptic (zero dead volume) sampling valves.
Industry Standards and Specifications
We build our systems in conformity with international quality and pharmacopoeia guidelines and deliver them with validation (DQ/IQ/OQ/PQ) documentation.
| Standard | Conductivity (µS/cm @25°C) | TOC (ppb) | Microbiological (CFU/mL) | Endotoxin (EU/mL) |
|---|---|---|---|---|
| USP Purified Water (PW) | ≤1.3 (Stage 1) | ≤500 | ≤100 | N/A |
| USP WFI (Water for Injection) | ≤1.3 | ≤500 | ≤0.1 | <0.25 |
| Ph. Eur. Purified Water | ≤5.1 | ≤500 | ≤100 | N/A |
| Ph. Eur. WFI | ≤1.3 | ≤500 | ≤0.1 | <0.25 |
| ISO 3696 Grade 1 | ≤0.10 | ~100 | N/A | N/A |
| ISO 3696 Grade 2 | ≤1.0 | ~500 | N/A | N/A |
| ASTM D1193 Type I | ≤0.056 | ≤50 | <0.01 | <0.03 |
| ASTM D1193 Type II | ≤1.0 | ≤50 | <0.10 | <0.25 |
Industry Applications
DI water is produced in different quality grades according to its intended use. Our solutions suit 7 main industries:
1. Pharmaceutical
USP/EP-compliant PW (purified water) and WFI (Water for Injection) production, cleanroom supply, and systems supported by full validation (IQ/OQ/PQ).
2. Food & Beverage
CIP systems, formulation (ingredient) water and process water: odorless and tasteless purified water production that meets ISO 22000 food safety requirements.
3. Energy / Power Plant
Low-conductivity purified water for boiler feed water, turbine condensate treatment and protection of high-pressure systems in line with EPRI standards.
4. Hydrogen Production
Electrolyzer feed water for green hydrogen projects; systems that meet ultrapure water requirements (≤0.1 µS/cm).
5. Chemicals & Petrochemicals
High-capacity deionized water, fully free of minerals, for critical process waters and sensitive cooling water systems.
6. Cosmetics
Hygienic purified water designs for shampoo, cream and lotion production lines under ISO 22716 Good Manufacturing Practices (GMP).
7. Electronics / Semiconductor
Ultrapure water (UPW) production systems of ASTM Type I (18.2 MΩ·cm resistivity) for critical component washing and microchip manufacturing.
Material and Design Requirements
Transferring high-purity water without contamination depends on choosing the right material. 316L SS (UNS S31603) stainless steel pipes, in line with sanitary piping standards, are preferred.
For pipe joints, orbital TIG welding is used instead of manual welding (with Ar ≥99.999% shielding gas). The inner surface roughness is set according to ASME BPE standards to prevent microbial attachment.
| ASME BPE Code | Ra (µm) | Area of Use |
|---|---|---|
| SF1 | 0.51 | Standard Purified Water (PW) line |
| SF4 | 0.38 | Critical WFI distribution line |
| SF5 | 0.51 | Electropolished PW line |
Loop Design Principles
- WHO TRS 970 & ISPE: Distribution lines are designed without dead legs (L≤3D), using zero-static diaphragm valves.
- To ensure turbulent flow (Reynolds > 4000), a continuous flow velocity (≥3 ft/sec or ≥1.0 m/s at the return) is maintained.
- Piping is installed with a slope of at least 1% for full drainability.
Sanitization Methods
Water systems must be sanitized periodically or continuously to prevent microbiological growth (biofilm formation). Depending on the intended use, we integrate the following sanitization methods into our systems:
Hot Water (Thermal) Sanitization
The system is freed of bacteria by heating the water to between 65°C and 85°C and circulating it through the line for 30 to 90 minutes. It is the most preferred method in WFI and pharmaceutical PW lines and leaves no residue.
Ozone (O₃) Sanitization
Ozone is an extremely strong oxidizer. In the loop line it is applied as continuous protection (0.02-0.05 ppm) or periodic shock dosing (0.2-0.5 ppm). Before the point of use, ozone is broken down within seconds into purified water with the help of a 254 nm UV unit, which prevents any effect on the final product.
Chemical Sanitization
CIP/sanitization performed periodically with peracetic acid (PAA), hydrogen peroxide (H₂O₂) or other approved chemicals. After application, detailed rinsing of the system and conductivity/residue monitoring are required.
Frequently Asked Questions about DI (Deionized) Water Systems
Common questions about deionized water production technologies, standards and applications.
What is DI water (deionized water)?
Deionized water is treated water of low conductivity from which dissolved ions (calcium, magnesium, chloride, sulfate and others) have been removed by ion exchange resins or electrodeionization (EDI). The conductivity level is defined by different standards depending on the application.
What is the difference between DI water and purified water (PW)?
Both terms refer to water from which ions have been removed; however, the term purified water (PW) in a pharmaceutical context means water that meets the specific limits defined by the USP and Ph. Eur. monographs (conductivity ≤ 1.3 µS/cm, TOC ≤ 500 ppb, bacteria ≤ 100 CFU/mL). DI water is a broader industrial concept and is classified according to different standards such as ASTM and ISO.
Which technologies are used to produce DI water?
The main technologies are ion exchange resins (cation and anion), mixed-bed resins, reverse osmosis (RO) and electrodeionization (EDI/CEDI). Modern systems favor an RO + EDI combination, which requires no chemical regeneration.
Which industries use DI water systems?
They are used in pharmaceuticals and biotechnology, food and beverage, power plants (boiler feed water), semiconductors and electronics, laboratory analytics and general industrial processes (washing, cooling, coating).
Should a resin-based system or EDI be preferred?
Resin-based systems have a lower investment cost but require periodic chemical regeneration. EDI (electrodeionization) regenerates the resins continuously with an electric current; it eliminates chemical use, provides uninterrupted production and lowers operating cost. EDI is recommended for pharmaceutical and high-purity applications.
How is DI water quality monitored?
It is monitored with continuous conductivity and TOC measurement. A rise in conductivity indicates resin or membrane exhaustion, and a rise in TOC indicates organic fouling. Online pH, temperature and flow measurement also verify system performance continuously.
Planning a project? Send us your flow rate, feed water source and target water quality to [email protected] — our engineers will reply with a technical proposal.