PURABAC USA
USP-Grade Formula
0.9% Benzyl Alcohol
Multi-Dose 30ml Vials
Same-Day Dispatch Mon–Fri
Ships All 50 States
For Research Use Only
WHAT IS BACTERIOSTATIC WATER
What Is Bacteriostatic Water for Injection (BWFI)?
Bacteriostatic Water for Injection, USP — commonly abbreviated as BWFI and known informally as "bac water" — is a sterile, non-pyrogenic aqueous preparation used in laboratory research as a multi-dose diluent or reconstitution solvent.
Every vial of PuraBac USA bacteriostatic water contains:
• Active ingredient: Water (H₂O) — 1 mL per 1 mL
• Inactive ingredient / preservative: Benzyl Alcohol 0.9% (9 mg/mL)
• pH: approximately 5.7 (range 4.5–7.0)
• Pyrogenicity: Non-pyrogenic — meets USP biological standards
• Container: Semi-rigid multi-dose polyolefin vial (ethylene/propylene copolymer)
• USP designation: Bacteriostatic Water for Injection, USP
What is bacteriostatic water and what does it contain?
The 0.9% benzyl alcohol (BnOH) preservative is what distinguishes bacteriostatic water from single-use sterile water. It inhibits bacterial growth within the vial after the rubber stopper is first punctured, allowing for multiple sterile withdrawals from a single vial, Making it the standard laboratory diluent for multi-dose research protocols.
Bacteriostatic Water for Injection, USP (bac water / BWFI) is a sterile, non-pyrogenic aqueous preparation consisting of water (H₂O) with 0.9% benzyl alcohol (9 mg/mL) as a bacteriostatic preservative. Its pH is approximately 5.7 (range 4.5–7.0). It is supplied in a multi-dose polyolefin vial that supports repeated laboratory withdrawals. The benzyl alcohol preservative inhibits bacterial growth after the vial stopper is punctured, Unlike single-use sterile water, which has no preservative. PuraBac USA supplies this product strictly For Research Use Only. Not for human use, consumption, or medical treatment.
How Bacteriostatic Water Works: The Role of Benzyl Alcohol
The defining feature of bacteriostatic water is its 0.9% benzyl alcohol (BnOH) preservative. Here is exactly how it works:
• Benzyl alcohol is a bacteriostatic agent; it inhibits bacterial growth rather than killing bacteria outright (bactericidal action).
• When the rubber stopper of a bacteriostatic water vial is punctured, benzyl alcohol slows microbial proliferation within the remaining solution.
• This bacteriostatic action extends the safe window for multiple withdrawals from a single 30ml or 10ml vial, reducing waste and supporting laboratory protocols that require repeated vial access.
• It does not eliminate contamination risk; aseptic technique must always be maintained.
Key chemical and physical properties:
Why does bacteriostatic water contain benzyl alcohol?
Benzyl alcohol is added at a concentration of 0.9% (9 mg/mL) to serve as a bacteriostatic preservative; it inhibits the growth of bacteria within the vial after the rubber stopper has been punctured. This is what makes bacteriostatic water suitable for multi-dose laboratory applications: the preservative keeps the solution protected between withdrawals. Without benzyl alcohol, each vial puncture would expose the solution to bacterial contamination risk, requiring the vial to be discarded after a single use. PuraBac USA supplies bacteriostatic water For Research Use Only. Not for human use or medical treatment.
Bac Water vs Sterile Water
Bacteriostatic Water vs. Sterile Water: What Is the Difference?
For laboratory research protocols requiring repeated vial access, bacteriostatic water is the appropriate multi-dose diluent. For single-withdrawal applications, sterile water may be preferred. Both products supplied by PuraBac USA are For Research Use Only.
How to Store Bacteriostatic Water: Shelf Life, Temperature & Laboratory Handling Guidelines
Before Opening (Sealed Vial)
• Store at controlled room temperature: 68–77°F (20–25°C); do not refrigerate unless your institutional SOP requires it.
• Keep away from direct sunlight, heat sources, and excessive humidity.
• Do not freeze: freezing may compromise the polyolefin container and benzyl alcohol preservative.
• Verify the printed expiration date upon receipt.
After First Vial Puncture
• Follow your institution's standard operating procedures (SOPs) for diluent discard timelines.
• Many laboratory protocols reference a 28-day guideline from the date of first puncture.
• Inspect before every withdrawal: discard if you observe cloudiness, floating particles, discoloration, container cracks, a damaged stopper, or any leakage.
• Use sterile syringes for each withdrawal and maintain aseptic technique at all times
How long does bacteriostatic water last after opening, and does it need to be refrigerated?
The widely referenced laboratory guideline for opened bacteriostatic water vials is to discard them within approximately 28 days of the first vial puncture. USP guidelines do not require refrigeration: sealed vials should be stored at controlled room temperature (68–77°F). After opening, some laboratory researchers refrigerate as an additional precaution, though this is not universally specified. Freezing is not recommended. Always follow your institution's SOPs. Unsealed vials should never be used if they show cloudiness, particles, discoloration, cracks, stopper damage, or leakage, or if the expiration date has passed.
For Research Use Only: This does not constitute medical guidance.
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