Sterile water vs distilled water: the difference

Sterile water is water that's been treated to remove living microorganisms — it's germ-free. Distilled water is water purified by boiling and condensing it to remove minerals and impurities, but distilling alone doesn't make it sterile. Germ-free and mineral-free are two different things.

Sterile water vs distilled water trips people up because both are "pure" water, but in different ways. One is about germs, the other is about minerals. That difference decides which is safe for what — and neither is the same as bacteriostatic water.

Written by bacwaterstar editorial team Reviewed by Jaspal Mann, Superintendent Pharmacist Last reviewed: September 6, 2026

How each one is made

Distilled water is made by boiling water into steam and condensing it back to liquid, which leaves minerals and many impurities behind. That makes it low in minerals, which is why it's used in appliances. Sterile water is made by a process that removes or kills microorganisms, such as heat sterilization or filtration. A water can be distilled without being sterile, and sterile without being distilled — the two processes solve different problems.

Sterile vs distilled vs bacteriostatic water, at a glance.

Property	Sterile water	Distilled water
Free of microorganisms	Yes (that's the point)	Not necessarily
Free of minerals	Depends on source	Yes (that's the point)
Typical use	Medical / wound care / injection-grade if USP	Appliances, CPAP, humidifiers, irons
Preservative	None	None

When they're not interchangeable

For anything medical, sterile matters. Distilled water from a grocery aisle isn't a substitute for sterile water in a clinical setting, because distilling doesn't guarantee it's germ-free. And for appliances that specify distilled water, using something else can leave mineral deposits. Match the water to what the task actually requires.

Where bacteriostatic water fits

Bacteriostatic water is a third thing again: sterile water for injection with a benzyl alcohol preservative added, so a multi-dose vial can be used more than once.¹ It's neither plain distilled water nor plain sterile water. If that's what you were actually looking for, start with our complete guide to bac water.

A note on safety. Don't assume "pure" means "safe to inject." Only water that is specifically sterile and injection-grade (USP) is appropriate for medical preparation, and even then only per the drug manufacturer's instructions.² When in doubt, ask a pharmacist.

Frequently asked questions

Is distilled water sterile?

Not automatically. Distilling removes minerals but doesn't guarantee the water is free of microorganisms.

Can I use distilled water instead of sterile water?

Not for medical uses. Distilled isn't guaranteed sterile, so it isn't a substitute where sterility matters.

Is either one the same as bacteriostatic water?

No. Bacteriostatic water is sterile injection-grade water with a benzyl alcohol preservative; neither distilled nor plain sterile water has that.¹

What is bac water? Bacteriostatic vs sterile

Sources

Bacteriostatic Water for Injection, USP — Description. DailyMed, U.S. National Library of Medicine. View label.
Bacteriostatic Water for Injection, USP — Warnings & Precautions. DailyMed. View label.