Bacteriostatic Water vs Sterile Water: What's the Difference?
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- Bacteriostatic water contains 0.9% benzyl alcohol; sterile water has no preservative.
- Bacteriostatic vials can be re-entered multiple times; sterile water is single-use.
- Both are filtered and sealed under sterile conditions.
- Choose bacteriostatic for repeated access, sterile for a single withdrawal.
They look identical in the vial, the names sound interchangeable, and both are "sterile water" — yet bacteriostatic water and sterile water are not the same product, and using the wrong one can quietly waste an entire vial. The difference comes down to a single ingredient. Here is what separates them, with a side-by-side table and guidance on which vial fits your laboratory work.
The short answer
Both are sterile, purified water filtered to remove microorganisms. The difference is the preservative: bacteriostatic water contains 0.9% benzyl alcohol; sterile water contains nothing but water. That one addition changes everything about how the vial is used — repeated access versus single use.
Side-by-side comparison
| Bacteriostatic Water | Sterile Water | |
|---|---|---|
| Preservative | 0.9% benzyl alcohol | None |
| Vial use | Multi-dose — repeated access | Single withdrawal, then discard |
| Use after opening | Repeated access from the sealed vial | Use promptly, do not re-enter |
| Sterile-filtered | Yes (0.22µm) | Yes (0.22µm) |
| Best for | Reconstitution needing repeated withdrawals | Preservative-free, single-use applications |
| Vial | Bacteriostatic Water 30 mL | Sterile Water |
Bacteriostatic water, explained
Bacteriostatic water is sterile water with 0.9% (9 mg/mL) benzyl alcohol added. Benzyl alcohol is a bacteriostatic agent: it inhibits the growth of most common bacteria. Because the preservative keeps the contents protected after the seal is broken, you can withdraw from the same sealed multi-dose vial repeatedly when it is handled aseptically. That makes it the practical choice whenever a single vial needs to last across several sessions. Our guide to bacteriostatic water in Australia covers what to look for in detail.
Sterile water, explained
Sterile water is purified water filtered and sealed under sterile conditions, with no preservative at all. With nothing to inhibit bacterial growth once the vial is opened, it is intended for a single withdrawal and should not be re-entered. That is exactly what you want when a preservative-free solution is required and benzyl alcohol would be unwanted.
Where saline fits in
There is a third option worth knowing: bacteriostatic sodium chloride 0.9%. It is the standard 0.9% isotonic concentration used as a laboratory diluent — with the same benzyl alcohol preservative, which is why it is a standard laboratory diluent and rinse. Think of it as the saline cousin of bacteriostatic water for work that calls for an isotonic solution rather than plain water.
Which one should you choose?
- Repeated withdrawals from one vial? Bacteriostatic water.
- One clean, preservative-free pull? Sterile water.
- Need an isotonic diluent? Bacteriostatic sodium chloride 0.9%.
Whichever you pick, how the vial is supplied still matters — see where to buy sealed, sterile-filtered vials in Australia. All products are for laboratory and research use only — not a therapeutic good and not for human or veterinary use.
Not sure which vial you need?
Browse bacteriostatic water, sterile water and saline — all sterile-filtered, for laboratory and research use only.
Shop all products →Frequently asked questions
Is bacteriostatic water the same as sterile water?
No. Both are sterile, but bacteriostatic water contains 0.9% benzyl alcohol while sterile water has no preservative. The preservative is what allows a bacteriostatic vial to be entered repeatedly.
Can I use sterile water instead of bacteriostatic water?
They serve different purposes. Sterile water suits single-use, preservative-free applications; bacteriostatic water suits multi-dose use where a sealed vial is accessed more than once.
Which vial should I choose?
Bacteriostatic water for repeated access, preservative-free sterile water for single use, and bacteriostatic sodium chloride 0.9% when you need an isotonic saline diluent.
All products supplied by Aus BAC Supply are for laboratory and research use only — not a therapeutic good and not for human or veterinary use. This article is general product information and is not medical advice.