Reference
Bac Water
"Bac water" is the common shorthand for bacteriostatic water — sterile, non-pyrogenic water containing 0.9% benzyl alcohol as a preservative. The two terms mean exactly the same thing; "bac" is simply an abbreviation of "bacteriostatic." The preservative inhibits bacterial growth, which is what lets a single multi-dose vial be drawn from repeatedly, conventionally for up to 28 days after the first puncture, instead of being discarded after one use.
For research and laboratory use only · Not for human or veterinary use
The essentials
- "Bac water" = bacteriostatic water — the same product, abbreviated
- Composition: sterile, non-pyrogenic water + 0.9% benzyl alcohol (9 mg/mL)
- Multi-dose: reusable up to 28 days after the first puncture
- Unopened shelf life: until the printed expiration date, typically 18–24 months from manufacture
- Common formats: 10 mL, 20 mL, 30 mL (BAC Water Depot supplies 10 mL Type I borosilicate glass)
- Unopened storage: controlled room temperature 20–25 °C (68–77 °F); excursions permitted 15–30 °C
- Not interchangeable with sterile water (single-use) or distilled/deionized water (not sterile specifications)
- Verify quality with a lot-specific Certificate of Analysis, not a generic one
Other names for bac water
All of the following refer to the same specification — sterile water preserved with 0.9% benzyl alcohol. Differences in wording are convention, not product.
| Term | Note |
|---|---|
| Bac water | Most common shorthand |
| BAC water | Capitalised variant — same product |
| Bacteriostatic water | The full, formal term |
| Bacteriostatic water for injection | Full label name of the specification |
| Bact water / bacterial static water | Common misspellings of the same thing |
Frequently asked questions
What is bac water?
"Bac water" is the common shorthand for bacteriostatic water — sterile, non-pyrogenic water containing 0.9% benzyl alcohol as a preservative. The two terms mean exactly the same thing; "bac" is simply an abbreviation of "bacteriostatic." The preservative inhibits bacterial growth, which is what lets a single multi-dose vial be drawn from repeatedly, conventionally for up to 28 days after the first puncture, instead of being discarded after one use.
Is bac water the same as bacteriostatic water?
Yes — they are the same product. "Bac water" is just the abbreviated form of "bacteriostatic water," the way it is usually written in research and lab-supply contexts. You may also see it written as "bacteriostatic water for injection," "BAC water," or "bact water." All refer to sterile water preserved with 0.9% benzyl alcohol.
What is bac water used for?
In laboratory and research settings, bac water is the standard diluent for reconstituting lyophilized (freeze-dried) compounds into solution. Its defining advantage over unpreserved diluents is that one vial can be entered multiple times over a period of days or weeks, because the benzyl alcohol suppresses bacterial growth between withdrawals.
What is the difference between bac water and sterile water?
The preservative. Sterile water for injection contains none, so once the vial is punctured it is single-use and the remainder is discarded. Bac water contains 0.9% benzyl alcohol, so the same vial stays usable across repeated entries for up to 28 days. Both begin sterile — only bac water is built to remain usable after the first entry.
Can I use distilled or deionized water instead of bac water?
No — they are different categories. Distilled and deionized water describe purification methods, not sterility. Neither is inherently sterile, non-pyrogenic, or preserved. Bac water is a finished sterile specification: purified, sterile-filtered, endotoxin-controlled, and preserved with benzyl alcohol.
How long does bac water last?
An unopened vial lasts until its printed expiration date, typically 18–24 months from manufacture. Once punctured, the conventional in-use window is 28 days — that limit reflects how long the preservative can reliably suppress growth through repeated entries, not the sterility of the sealed vial.
How should bac water be stored?
Sealed, at controlled room temperature — USP defines this as 20–25 °C (68–77 °F), with excursions permitted between 15–30 °C (59–86 °F) — protected from direct light, per the vial label. A sealed vial does not require refrigeration. After the first puncture, follow the storage instruction on your vial label. Keep the stopper clean and use aseptic technique on every entry, since the preservative inhibits bacterial growth but does not sterilize contamination introduced by a dirty needle.
What sizes does bac water come in?
Common multi-dose formats are 10 mL, 20 mL, and 30 mL, supplied in glass or plastic vials with a rubber stopper. The 10 mL vial is the standard research-supply unit and the format BAC Water Depot supplies, in Type I borosilicate glass — the pharmacopoeial standard for injectable containers.
How do I know bac water is genuine and properly tested?
Ask for a lot-specific Certificate of Analysis — a CoA issued for the exact production lot you received, not a generic sample document. A complete CoA reports sterility (USP <71>), bacterial endotoxins (USP <85>), particulate matter (USP <788>), and a benzyl alcohol assay, each against its specification. If a supplier cannot produce a CoA for your lot number, that is the signal to walk away.
Where can I buy bac water?
Bac water is sold by research and laboratory supply vendors in the United States. When comparing suppliers, the things that actually differentiate them are lot-specific third-party CoAs, domestic US manufacturing and shipping (a domestic order never passes through customs), and transparent per-vial pricing. BAC Water Depot supplies 10 mL multi-dose vials manufactured in the USA with a lot-specific Certificate of Analysis and same-day US dispatch.
Buying bac water
BAC Water Depot supplies research-grade bac water in 10 mL multi-dose vials — manufactured in the USA in an ISO 9001:2015 registered facility, tested per lot by an independent third-party laboratory, with a lot-specific Certificate of Analysis reachable by scanning the QR code on the vial. Single vials from $9.99, with bulk tiers down to $6.49 per vial. Same-day US dispatch on orders placed before 2:00 PM CT.
Comparing prices? Bac water for sale — current single-vial, 10-pack, and bulk pricing in one place.