Deionized Water Guide: Is It Safe To Drink? – Frizzlife

Deionized water removes mineral ions through ion exchange to deliver ultra-low conductivity water for labs, electronics, and industrial processes. But can you drink deionized water, how is it different from distilled water, and which system is right for you? This guide gives fast answers up front, then explains processes (DI vs distilled vs reverse osmosis), purity metrics, health considerations, applications, standards, selection, maintenance, costs, sustainability, and case examples. Use our comparison tables, simple calculators, and checklists to choose, run, and care for a system with confidence. Whether you need ASTM-grade laboratory water or spot-free rinsing for detailing, you’ll find data-backed insights, expert tips, and actionable steps.

What Is Deionized Water?

Deionized and distilled water are both highly purified water, but made using different processes. Deionized water, known as DI water, is a type of water that has had charged mineral ions removed by ion exchange. Resins swap ions in the water—like calcium, magnesium, sodium, chloride, and sulfate—for H+ and OH-, which combine to form pure H2O. The result is water with very low conductivity (or high resistivity), which is why it’s used wherever trace ions cause problems. If you’ve ever seen “Type I” or “ultrapure water,” that often means DI water that meets strict lab standards.

Is deionized water safe to drink daily?

You can drink deionized water in small amounts, but deionized water may not be ideal as your daily drinking water. Water is safe to drink in moderation, but water lacks minerals. It has no calcium or magnesium, tastes flat, and can be “aggressive,” which means it may leach metals from household plumbing if used that way. Health agencies favor mineral-containing drinking water. In short: occasional sips are fine; don’t use deionized water as your only long-term drinking water. For households concerned about safety or taste, it’s wise to install a home water filter to remove contaminants and maintain balanced minerals.

When should you not use DI water?

Avoid DI water as your only drinking water. Do not run it through unlined metal pipes or fittings that can corrode, because deionized water enter and leach metals from plumbing aggressively. Also avoid using DI alone where sterile water is required unless you add proper microbial controls (for example, UV and 0.2 µm final filtration).

Deionized Water Vs Distilled Water Vs Reverse Osmosis Water: Which Is Purer?

When comparing deionized water vs reverse osmosis water vs distilled water, the “purest” option depends on what you want to remove. Each purification method excels in different areas of water chemistry and microbiological control.

Deionized (DI) water

Deionized (DI) water is produced by running water through ion-exchange resins that strip out charged particles—like calcium, magnesium, chloride, and sulfate—resulting in extremely low ion content. When further polished, DI water can produce high purity water, with resistivity up to 18.2 MΩ·cm, making it ideal for laboratories and electronics manufacturing, making it ideal for laboratories, electronics manufacturing, and pharmaceutical use. However, DI systems don’t effectively remove organic compounds or microbes unless paired with other treatments like reverse osmosis or UV sterilization. The taste of deionized water is flat due to the lack of minerals from water.

Distilled water

Water distillation purifies water by boiling and condensing. This process removes most dissolved solids, heavy metals, and microbes by converting water into vapor and collecting the pure condensate. It’s highly effective against biological contaminants but less efficient at removing volatile chemicals. Distillation also consumes more energy and time, making it less practical for large-scale or daily household use.

Reverse osmosis (RO) water

Reverse osmosis (RO) water is produced by forcing water through a semi-permeable membrane that blocks most dissolved solids, organic matter, and microbes. It’s often considered the most versatile purification method for residential systems. In fact, many high-purity setups combine reverse osmosis and deionization—first using RO to remove 95–99% of contaminants, then using DI as a final polishing step. This RO + DI hybrid setup offers cost efficiency and exceptional purity for both industrial and laboratory use.

So, which is purer—deionized water vs reverse osmosis water or distilled water?

For ion removal, DI water wins.
For microbial control, distillation or RO combined with UV filtration performs better.
For everyday home use, RO water provides the best balance between purity, practicality, and cost.

In short, deionized water vs reverse osmosis water is not a competition of better or worse—it’s about application. DI shines in precision environments, while RO excels in safe, consistent, and affordable drinking water purification.

Purification Methods Explained: Ion Exchange, Distilled Water, Reverse Osmosis

All three methods purify water but in different ways. Ion exchange removes charged ions, distillation uses heat to separate pure water, and reverse osmosis filters it through a membrane. Each has unique strengths and is often combined for ultra-pure results.

Ion-exchange resins and EDI

Ion exchange uses two resin types:

A cation resin swaps positive ions (Ca2+, Mg2+, Na+) for H+.
An anion resin swaps negative ions (Cl-, SO4^2-, NO3-) for OH-.

Systems may use:

Separate two-bed (cation then anion) tanks,
Mixed-bed polishing (resins blended for final high purity),
Electrodeionization (EDI), which uses electricity and ion-selective membranes to continuously remove ions without chemical regeneration. EDI loves a low-TDS feed, so it often follows RO.

Pros:

Fast, compact, and cost-effective for ion removal.
Achieves very low conductivity and high resistivity.

Cons:

Weak on organics and microbes unless paired with pretreatment (carbon, RO) and post-treatment (UV, ultrafiltration).
Conventional resin beds need chemical regeneration or replacement.

Distillation and microbial control

Distillation boils water and condenses the steam. This step removes most minerals and many contaminants, and it also kills microbes. It is reliable but:

Uses more energy,
Has slower throughput,
Needs regular cleaning to remove scale.

Distilled water is common for autoclaves, sterilizers, and some medical device instructions because of the combination of low minerals and heat-driven microbial control.

Reverse osmosis and pretreatment trains

Reverse osmosis (RO) pushes water through a semi-permeable membrane. It removes most dissolved solids, a large share of organics, and many microbes. RO works best with pretreatment such as:

Sediment filtration,
Activated carbon (for chlorine, chloramines),
Softening or anti-scalant (to limit scale),
Sometimes UV (to control microbial growth upstream).

RO is a strong “backbone” technology. Many systems use RO first, then DI or EDI to reach very low conductivity.

Table: Summary comparison of processes

Process	Ion removal	Microbial control	Typical purity (resistivity at 25°C)	Energy use (kWh/gal, small systems)	Relative cost per gallon	Notes
Ion exchange (DI)	Excellent for ions	Limited without UV/filtration	1–18.2 MΩ·cm (with polishing)	~0.005–0.02	Low–Medium	Needs resin maintenance; best after RO
Electrodeionization (EDI)	Excellent for ions	Limited without UV/filtration	10–18.2 MΩ·cm (with RO feed)	~0.01–0.05	Medium	Continuous; no chemical regeneration
Distillation	Very good for minerals	Strong (boiling)	~0.5–10 MΩ·cm	~2–6	Medium–High	Slower; periodic descaling
Reverse osmosis (RO)	Very good (95–99% TDS)	Good with final 0.2 µm/UV	~0.05–1 MΩ·cm	~0.02–0.06	Low	High recovery varies; needs pretreatment

Values are typical ranges and depend on system design, temperature, and maintenance.

Purity Metrics And Water Chemistry Essentials

To understand how clean your water really is, you need to know a few key metrics. Conductivity, resistivity, and TDS reveal how many ions remain in the water and how pure it is. These numbers are the universal language of water quality—used in labs, manufacturing, and filtration system design. Let’s look at what each means and how they connect.

Conductivity, resistivity, and TDS explained

Conductivity measures how well water carries electric current. Units: µS/cm (microsiemens per centimeter). Lower is purer.
Resistivity is the inverse of conductivity. Units: MΩ·cm (megaohm-centimeter). Higher is purer. Ultrapure water at 25°C has 18.2 MΩ·cm.
TDS (total dissolved solids) is the mass of dissolved ions, often shown as mg/L or ppm.

Quick ranges:

Tap water: 200–800 µS/cm (0.001–0.005 MΩ·cm), TDS 100–500 ppm (varies widely).
RO permeate: 5–50 µS/cm (0.02–0.2 MΩ·cm).
DI polished: 0.055–1 µS/cm (18.2–1 MΩ·cm).

Table: Common lab water grades (typical targets)

Grade	Conductivity (µS/cm, 25°C)	Resistivity (MΩ·cm, 25°C)	TOC (ppb)	Microbes (CFU/mL)
ASTM Type I	≤ 0.056	≥ 18.2	≤ 50	≤ 10
ASTM Type II	≤ 1.0	≥ 1.0	≤ 50	≤ 100
ASTM Type III	≤ 5.0	≥ 0.2	≤ 200	—
ISO 3696 Grade 1	≤ 0.1 (at 20°C)	≥ 10	≤ 50	—
ISO 3696 Grade 2	≤ 1.0	≥ 1	≤ 50	—
ISO 3696 Grade 3	≤ 5.0	≥ 0.2	—	—

Standards specify more details (like silica). Always check the latest official text for your compliance needs.

Ionic vs microbial purity

Ion-free does not mean sterile. A DI bed can actually become a place where bacteria grow if the system is idle or warm. If you need micro-safe water, add:

UV (254 nm) to disrupt DNA,
0.2 µm final filters,
Good circulation and regular sanitization.

pH drift and CO2 absorption

Fresh deionized water is very low in ions, so its pH can shift quickly. When exposed to air, it absorbs CO2, forming carbonic acid. The pH can drop into the 5.5–6.5 range even though the water is still very low in contaminants. That’s normal. To limit drift, use tight lids, short storage times, and low-CO2 headspace if the pH matters for your work.

Fast converter for everyday use:

Step 1: Measure conductivity (µS/cm) at 25°C.
Step 2: Pick a factor k between 0.5 and 0.7 (0.5 for low TDS, 0.65 for typical tap).
Step 3: TDS (ppm) ≈ k × conductivity (µS/cm).

Example: 10 µS/cm × 0.65 ≈ 6.5 ppm TDS.

To check grade: Compare your measured resistivity or conductivity to the table above.

Health And Drinking Considerations (Distilled Water, Ro, Demineralized)

Water is a great resource, essential for labs, electronics, industrial processes, and daily life. When it comes to drinking very pure water, not all purification methods are equal. Distilled, reverse osmosis, and deionized water can all be safe in moderation, but they differ in mineral balance, taste, and how they interact with plumbing and the body. Understanding these differences helps you choose what’s best for daily hydration versus technical or medical use.

Minerals, taste, and potential leaching

“Can I drink deionized water?” Yes, you can drink it in small amounts, but it’s not the best choice as your daily water. Here’s why:

No minerals: Tap water contains calcium, magnesium, and other beneficial ions, but DI water is stripped of these, making it taste flat and potentially leach metals from plumbing.
Flat taste: Many people find it bland.
Leaching risk: Low-mineral water can pick up metals from plumbing. That’s why health guidelines favor water with some mineral content for routine drinking and discourage using DI as the sole long-term source.

When occasional consumption is acceptable

If you take a sip in a lab, or you drink a glass because it’s what’s on hand, that’s fine for most healthy adults. For regular hydration, use tap, filtered, or mineral water that meets drinking water standards. If taste is a problem with RO or distilled, a remineralization step can help.

Does DI water hydrate better or worse than tap water?

Benefits and risks of deionized water should be understood before replacing tap or bottled water with DI water.

Hydration: Your body absorbs it about the same as other clean water.
Electrolytes: Deionized water doesn’t supply electrolytes. Get those from food or an oral rehydration mix when needed.
Bottom line: Hydration is similar, but DI is not a good long-term replacement for normal drinking water. Water used for daily consumption should contain minerals.

For policy and health limits, see the WHO Guidelines for Drinking-water Quality and your national drinking water rules (linked at the end).

Real-World Applications And Industry Use Cases

Water is commonly used in laboratories, electronics, automotive, and healthcare settings. Deionized and purified water play vital roles far beyond drinking—they’re essential wherever minerals or impurities could disrupt performance, accuracy, or safety. From labs and pharmaceutical plants to electronics, automotive, and healthcare settings, each industry tailors its water purification setup to meet precise standards. Let’s look at how different sectors use DI and ultra-pure water in practice.

Laboratories and pharmaceuticals

DI water supports clean baselines for reagents, buffers, and standards. Using this type of water can reduce background noise in sensitive tests and keeps instruments free from mineral deposits. Labs often target ASTM Type I or Type II water. Pharmaceutical facilities follow USP water quality expectations with strict microbial and TOC controls, and they document sanitation, monitoring, and change control. Remember that Water for Injection (WFI) has extra microbial and endotoxin limits; it’s a different category than simple DI.

Electronics and semiconductors

Microchips and circuit boards hate ions and particles. Ultrapure water rinses between steps help keep yields high. Cooling systems may use low-conductivity water to reduce stray currents and corrosion. Typical designs use RO + EDI + UV + submicron filtration, plus loop circulation to maintain purity at the points of use.

Automotive and appliances

Lead-acid batteries, boiler feedwater, and steam irons run cleaner with deionized water because it avoids scaling and corrosion from minerals. Car detailers use DI for spot-free rinsing so there’s no white residue when water dries. Autoclaves and sterilizers often call for DI or distilled to prevent scale.

what happens if you drink deionized water

Medical, dental, and healthcare devices

Sterilizers, dental units, endoscope washers, and CPAP humidifiers often specify distilled or demineralized water to protect equipment and support hygiene. Always follow the device manual. Where patient safety is involved, add microbial controls and storage hygiene, not just ion removal.

Standards, Compliance, And Quality Control

Water purity isn’t just about the numbers—it’s about meeting recognized standards and proving consistency through monitoring and documentation. Laboratories, semiconductor fabs, and pharmaceutical plants all follow strict frameworks to ensure reliability and safety. Here’s how global standards like ASTM, ISO, and USP define quality grades and guide proper validation and recordkeeping.

ASTM, ISO, and lab water grades

Most labs reference ASTM D1193 (Types I–III) or ISO 3696 (Grades 1–3). These set limits for conductivity/resistivity, TOC, and sometimes bacteria and silica. Your method SOP should state which grade is required at each step (for example, Type I for final sample rinse, Type II for glassware washing, Type III for feedwater).

Semiconductor and pharma considerations

Semiconductor plants follow SEMI guidance for ultrapure water used in wafer fabs. Pharma follows GMP and USP expectations for Purified Water and WFI, including documentation, training, and validated cleaning and monitoring. In both cases, the paper trail matters as much as the purity numbers.

Monitoring and validation

Inline meters for conductivity/resistivity at key points,
Periodic TOC checks,
Microbial sampling at storage and points of use,
Meter calibration on set intervals,
Alarm limits and corrective actions in your SOPs.

A simple rule: if you don’t measure it, you can’t claim it. Keep logs.

QC essentials checklist

Define required grade (ASTM/ISO/USP).
Place calibrated conductivity/resistivity meters before and after polishing.
Add TOC and microbial checks to the schedule.
Sanitize on a fixed cadence (document it).
Train staff on sampling SOPs.

System Selection And Buying Guide (Specs, Capacity, Flow)

Choosing the right water filtration system starts with knowing your water quality goals and usage needs. Whether you’re outfitting a lab, factory, or workshop, factors like feedwater quality, required purity level, and daily volume all shape your setup. The right mix of RO, DI, or EDI stages can balance cost, performance, and maintenance. Here’s how to plan, compare specs, and match a system to your real-world requirements.

Needs assessment framework

Ask yourself:

What’s my feedwater like? Get a basic analysis (TDS, hardness, chlorine/chloramine, silica, microbes).
What purity do I need (Type I/II/III or ISO Grade 1/2/3)?
How many liters per day? What’s the peak flow?
Do I need microbial control (UV, 0.2 µm filter, recirculation)?
Will I store water? How big is the tank? Closed loop or open?
Do I need documented compliance (GMP/USP, SEMI)?

System types and configurations

Two-bed DI (cation + anion) for moderate purity.
Mixed-bed DI for polishing to very low conductivity.
RO + DI for cost-effective high purity.
RO + EDI + UV + 0.2 µm for continuous high purity with minimal chemicals.
Portable exchange tanks (vendor swaps spent tanks) for sites that cannot regenerate on-site.

How to read specifications

Grain capacity or bed volume: how much ion load the resin can handle.
Recovery ratio (RO): product vs. reject water; higher recovery saves water.
Pressure and temperature limits: protect membranes and resins.
Cartridge sizes and change intervals: plan stocking and maintenance.
Resistivity/TOC at point of use: the metric that matters for your work.

Interactive tools

Selection mini-wizard:

If feed TDS > 300 ppm and hardness is high, start with softening or anti-scalant, then RO, then DI/EDI.
If you need Type I for sensitive assays, add mixed-bed polishing, UV, and 0.2 µm filtration with a recirculating loop.
If your need is spot-free rinsing or batteries, a small DI system or portable exchange tank may be enough.

Simple cost-of-ownership sketch:

CAPEX: equipment + installation.
OPEX: filters, resins or EDI power, RO membranes, sanitizers, energy, water/waste.
Tip: Using RO before DI can cut resin spend by 60–90% because fewer ions reach the resin.

Maintenance, Safety, And Troubleshooting

Keeping a water purification system running smoothly isn’t just about replacing filters—it’s a combination of pretreatment, resin care, microbial control, and regular checks. Understanding how each component behaves, knowing common warning signs, and following a routine maintenance plan helps prevent downtime, extend equipment life, and ensure consistent water quality. Here’s a quick guide to staying ahead of problems.

Pretreatment best practices

Protect your downstream equipment:

Sediment filter to catch rust and sand,
Carbon to remove chlorine/chloramines that damage RO membranes and resins,
Softener or anti-scalant to reduce scale,
Keep inlet pressure and temperature within spec.

Resin lifecycle management

Watch for “breakthrough” (rising conductivity at the outlet).
Use color-changing or monitored mixed-bed cartridges where possible.
Replace or regenerate on schedule, not only when quality drifts.
Keep spare cartridges dry, sealed, and out of sunlight.

Microbial control and sanitation

Add UV disinfection in the loop,
Use 0.2 µm point-of-use filters,
Sanitize tanks, lines, and resins as the SOP dictates,
Keep a closed, opaque storage tank; circulate to prevent stagnation,
Replace filters and lamps on time.

is deionized water the same as distilled water

Troubleshooting flowchart (symptoms → likely causes → fixes)

Rising TDS or falling resistivity → exhausted resin, bypass leak, high CO2 → swap resin, check seals, use CO2 scrubber or vent.
Taste/odor or biofilm → stagnant tank, old filters → sanitize, change filters, add UV, increase recirculation.
Low flow → clogged prefilter, fouled RO membrane → change filters, flush or replace membrane.
Corrosion spotted → DI in copper/galvanized, low pH from CO2 → switch to HDPE or stainless, reduce air exposure, add degassing step.

Cost, Sustainability, And Environmental Impact

When choosing a water purification method, it’s important to weigh energy use, water waste, and chemical impact alongside upfront costs. Distillation, reverse osmosis system, and DI/EDI systems all differ in efficiency, throughput, and environmental footprint. Understanding these factors helps you pick a system that balances performance, operating expenses, and sustainability for your specific needs.

DI vs distilled vs RO: energy and water footprint

Method	Energy use (kWh/gal, small systems)	Wastewater ratio (waste:product)	Throughput	Notes
Distillation	~2–6	~0:1	Low	High energy; no membrane waste
RO	~0.02–0.06	~1–4:1 (setup-dependent)	Medium	Efficient; reject can be reused for non-critical tasks
DI (resin)	~0.005–0.02	Minimal during run; regenerant waste offsite or onsite	High	Chemical regenerants if not EDI
EDI	~0.01–0.05	~0:1 during operation	High	No chemical regeneration; prefers RO feed

Values vary by scale, design, and temperature. Always model your site.

Waste and chemical handling

Spent resin and regenerant brine must be handled and disposed of per local rules.
Many suppliers offer resin return and recycling programs.
Keep acids and caustics in labeled, compatible containers with secondary containment.
Train staff and keep SDS sheets on hand.

Eco-optimizations

Use RO recovery tuning to cut waste (add permeate recirculation if supported).
Consider EDI for continuous operation with fewer chemicals.
Add smart meters to catch leaks and optimize flush cycles.
Reuse RO reject for toilets, irrigation, or cleaning where allowed.

OPEX/CAPEX comparison table (typical, small systems)

Configuration	CAPEX	OPEX	Notes
Countertop distiller	Low	Medium–High (energy)	Simple, slow
RO under-sink	Low–Medium	Low (filters, some waste)	Good base purity
RO + DI cartridge	Medium	Low–Medium (resin)	Very low ions
RO + EDI + UV + 0.2 µm	Medium–High	Low–Medium (power, lamps, filters)	Continuous, high purity

Use a 3–5 year horizon to compare total cost, not just purchase price.

Case Studies And Actionable Takeaways

Real-world examples show how choosing the right water purification setup can improve performance, reduce maintenance, and ensure quality. From labs to electronics lines and boiler systems, proper system design and upkeep make a measurable difference. These case studies highlight key lessons and practical steps you can apply when selecting, operating, or upgrading your water system.

Data-backed case examples

Lab analytics: A chemistry lab moved from RO-only to RO + mixed-bed DI. Resistivity at the tap rose from about 0.2 MΩ·cm to 15–18 MΩ·cm, and ionic background in trace assays dropped. Glassware also showed fewer mineral spots after washing.
Electronics rinsing: A board assembly line added UV and 0.2 µm final filters to an existing DI loop. Micro counts at points of use fell to within method limits, improving rinse consistency and reducing rework.
Boiler feed: A facility switched from softened water to RO + DI for high-pressure boilers. Scale inspections showed cleaner tubes and longer intervals between acid cleanings, helping maintain heat transfer.
These are typical outcomes when systems are sized and maintained correctly. Your site results depend on feedwater, configuration, and SOPs.

Storage and safety checklist

Use compatible materials: HDPE, PP, PVDF, or 316 stainless for tanks and lines.
Keep tanks opaque or shaded; limit light to reduce algae growth.
Use tight lids and vents with filters or CO2 scrubbers if pH matters.
Circulate the loop to prevent stagnation; avoid dead legs.
Add UV and 0.2 µm final filters if microbial control is needed.
Sample with sterile bottles and clean technique; log results.
Install backflow prevention on feed lines.

Bottom line and next steps

Deionized water is used when ionic purity drives your results. If you need microbial control too, add UV and final water filters.

If you need clean water at home, reverse osmosis is a practical choice; add a remineralization cartridge for taste.
If a device manual specifies distilled or demineralized water, follow it to protect the equipment and meet hygiene goals.
For labs and regulated sites, tie your system to ASTM, ISO, USP, or SEMI targets, monitor inline, and document everything.

Want a quick selector?

Need the lowest ions for sensitive assays or wafer rinses? RO + DI/EDI + UV + 0.2 µm.
Need reliable micro control for sterilizers? Distilled or RO + UV + final filtration.
Need spot-free rinsing or batteries? DI cartridge or portable exchange tanks.
Need general clean water for the office or lab wash-up? RO with carbon and sediment pretreatment.

FAQs

1. Is deionized water the same as distilled water?

Not quite. Deionized water (DI) and distilled water can both be extremely pure, but they’re made in totally different ways. DI water is produced using ion exchange resins that specifically remove charged particles like calcium, magnesium, and chloride. Distillation, on the other hand, involves boiling the water and collecting the steam, which leaves behind most contaminants—including minerals, salts, and many microbes. Both can reach very low total dissolved solids (TDS) levels, but distillation is better at eliminating bacteria and organic compounds, while deionization excels at removing ions and dissolved salts. In short: they can look and test similarly pure, but they take very different paths to get there.

2. What happens if you drink deionized water?

Drinking a small amount of deionized water won’t hurt you—it just tastes flat or slightly odd because it lacks minerals that give regular water its flavor. However, if you were to drink only DI water long-term, that’s not recommended. It doesn’t provide essential minerals like calcium and magnesium, and it can be slightly more aggressive in dissolving trace metals from pipes or containers. So while it’s fine occasionally or in lab settings, it’s not meant to replace your everyday drinking water. Think of it as “empty” water—super clean, but not naturally balanced for health.

3. Which is better, reverse osmosis or deionized water?

It depends on what you need. Reverse osmosis (RO) is great for home and general use because it removes a wide range of contaminants—not just ions, but also microbes, sediments, and organic compounds. Deionized water, however, is the winner when it comes to removing charged ions and achieving ultra-pure water. In fact, many high-purity setups combine both: RO first, then DI. The RO handles the heavy lifting by removing most impurities, and the DI stage “polishes” the water to near-zero conductivity. So, if you’re asking “deionized water vs reverse osmosis water: which is purer?”—the answer is DI, but RO is more practical for everyday home filtration.

4. What is deionized water used for?

Deionized water has a ton of specialized uses. You’ll find it in laboratories, electronics manufacturing, and medical facilities because it doesn’t leave behind mineral residues that can interfere with experiments or delicate equipment. It’s also used for automotive batteries, steam irons, boilers, aquariums, and spot-free car rinsing—basically anywhere minerals could cause buildup or conductivity issues. Even photographers and cosmetic manufacturers use it as a neutral base for mixing chemicals or products. Whenever purity and zero residue matter, DI water is the go-to.

5. How is deionized water made?

Deionized water is made through a chemical filtration process rather than a physical one like boiling. The water is passed through ion-exchange resins that trap unwanted ions and swap them for hydrogen (H⁺) and hydroxide (OH⁻) ions. These combine to form pure water molecules (H₂O). To reach even higher purity, many systems include a reverse osmosis (RO) pre-filter, followed by a mixed-bed resin or electrodeionization (EDI) stage for polishing. The result is water with extremely low conductivity and almost zero dissolved solids—perfect for precision use where even tiny amounts of minerals could cause issues.

References

WHO Guidelines for Drinking-water Quality: https://www.who.int/publications/i/item/9789241549950

ASTM D1193 (laboratory water): https://www.astm.org/d1193-06r18.html

ISO 3696 (water for analytical laboratory use): https://www.iso.org/standard/9169.html