Is Deionized Water the Same as Distilled Water?
Short answer
No, but they are close. Distilled water is made by boiling water and condensing the steam, which leaves minerals behind. Deionized water is made by passing water through ion-exchange resin that pulls dissolved minerals out. Both are very low in minerals, so for batteries, steam irons, humidifiers and spot-free rinsing they do the same job.
How distilled water is made
Distillation is the oldest way to purify water. Water is heated until it boils, the steam rises away from the dissolved minerals, and the steam is cooled back into liquid in a separate container. Calcium, magnesium, iron and other dissolved solids stay behind in the boiler. Because it takes a lot of energy to boil water, distillation is slow and comparatively costly at scale.
How deionized water is made
Deionization uses chemistry instead of heat. Water flows through beds of ion-exchange resin. Cation resin captures positively charged minerals such as calcium, magnesium and sodium and releases hydrogen ions. Anion resin captures negatively charged ions such as chloride, sulfate and bicarbonate and releases hydroxide ions. The hydrogen and hydroxide combine into more water (Xylem; Lenntech). The result is water with its dissolved minerals removed, made quickly and without boiling.
| Deionized water | Distilled water | |
|---|---|---|
| How it’s made | Ion-exchange resin removes dissolved mineral ions | Water is boiled and the steam is condensed |
| Dissolved minerals | Very low | Very low |
| What it doesn’t remove well | Uncharged substances, such as some organics | Substances that boil off with water |
| Speed and energy | Fast, no boiling | Slow, energy intensive |
| Common uses | Batteries, irons, humidifiers, spot-free rinse, aquariums, soap making | Batteries, irons, humidifiers, appliances |
So which should you use?
For household jobs, the thing that matters is the minerals. Minerals are what cause white spots on glass and paint, scale in steam irons, white dust from ultrasonic humidifiers and buildup on battery plates (USGS). Deionized and distilled water both remove them, which is why battery makers such as Trojan list either one for topping off flooded batteries (Trojan Battery).
- Car, golf cart and solar batteries: either works. See Renew Labs Battery Water and our car battery water guide.
- Steam irons and garment steamers: either works, but check your manual. Some makers prefer a 50/50 mix with tap water. Read what water to use in a steam iron.
- Humidifiers: either reduces white dust. See our humidifier water guide.
- Spot-free car and glass rinsing: deionized water is the standard in detailing. See Car Wash & Glass Spot-Free Rinse.
What about reverse osmosis and tap water?
Reverse osmosis forces water through a membrane that blocks most dissolved solids but not all of them, so RO water is often finished with a deionization stage when a spot-free result matters. Tap water and most filtered or bottled waters keep their minerals. Pitcher filters improve taste but don’t remove hardness. Our deionized water guide compares deionized, distilled, RO and tap water side by side.
Renew Labs water is sold for household, automotive, garden and hobby uses and is not for drinking.
Related questions
Can I use deionized water instead of distilled water?
Yes, for most household uses that call for distilled water, including batteries, irons, humidifiers and coolant mixing. Both are low in minerals. Always follow your appliance maker’s directions. Shop Renew Labs Deionized Water.
Is deionized water purer than distilled water?
They remove different things. Deionization is very effective at removing dissolved mineral ions, while distillation also leaves behind many non-ionic substances. For mineral-related problems such as scale and spots, both work well.
Is DI water the same as demineralized water?
In everyday use, yes. Deionized and demineralized both describe water with its dissolved minerals removed, usually by ion exchange.
How can I tell if water is deionized?
Use an inexpensive TDS or conductivity meter. Water conducts electricity because of dissolved ions, so deionized water reads very low (USGS).
Shop Renew Labs deionized water
Made in Houston, Texas, and packed for the job you need it for.
Sources
Researcher resources
- Shop Bacteriostatic and Sterile Water
- View Our Certificate of Analysis
- Free Reconstitution Calculator
- Compare BAC Water Products
Keep reading
- What Is a Beyond-Use Date (BUD)?
- Can You Use Tap Water in an Ultrasonic Diffuser?
- What Is ICP-MS Testing?
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