Bacteriostatic water, often shortened to BAC water, is sterile water that contains a small amount of a preservative. In laboratory settings it is used as a diluent where material will be accessed more than once from the same vial.
What is in it
Standard bacteriostatic water is sterile, non-pyrogenic water containing 0.9% benzyl alcohol. The benzyl alcohol acts as a bacteriostatic preservative, meaning it inhibits the growth of most bacteria that might be introduced by repeated needle or pipette access. It does not make the water sterile after contamination, and it is not a substitute for good aseptic technique.
Why a preservative matters
Plain sterile water has no preservative, so once a vial is opened it should be treated as single use. When a vial will be accessed over several sessions of an experiment, a preserved diluent reduces the risk that accidental contamination will multiply between uses.
Basic handling notes for the lab
- Keep it aseptic. Wipe the stopper with alcohol before each access and use sterile, single-use tools.
- Label and date. Write the date first accessed on the vial and discard according to your protocol.
- Check compatibility. Benzyl alcohol is not suitable for every application, so check that a preserved diluent fits your assay.
- Store sensibly. Follow the storage guidance on the vial label and keep it away from heat and direct light.
Our bacteriostatic water
FirePepLabs supplies BAC water in a 3 mL vial for laboratory use. For storage of dry material, see our guide to storing lyophilized research peptides.
For laboratory research use only. Not for human or veterinary use. This article is general educational information for researchers and is not medical advice.