Bac Water, Sterile Water or Acetic Acid Water: Which Diluent to Order
By the BacWater.fit team · Updated
Short answer. Bac water (sterile water with 0.9% benzyl alcohol) suits vials you will draw from more than once. Sterile water has no preservative: use it once, or wherever benzyl alcohol must be avoided. 0.6% acetic acid water (pH 2.7–3.1) is for the few materials whose documentation calls for a dilute acid.
| Bacteriostatic water | 0.9% (v/v) benzyl alcohol · multi-dose · discard 28 days after first puncture · pH 5.0–7.0 |
|---|---|
| Sterile water | No preservative · single use · pH 5.0–7.0 |
| 0.6% acetic acid water | 0.6% (v/v) acetic acid · single use · pH 2.7–3.1 |
Start from the material's documentation
The datasheet or method for the material you are dissolving is the authority. If it names a diluent, use that one; if it excludes benzyl alcohol, use sterile water.
Choose bac water when
- You will draw from the same vial over days or weeks.
- Nothing in your method rules out benzyl alcohol.
Choose sterile water when
- Benzyl alcohol must be avoided.
- You use the whole vial at once.
Choose acetic acid water when
- The documentation asks for a dilute acid, usually because the material does not dissolve at neutral pH.
- You can use the vial in one go — it has no preservative.