Bacteriostatic Water (BAC Water)
Also known as: BAC water, BAC Water
Bacteriostatic water is sterile water containing 0.9% benzyl alcohol as a preservative. It is the standard diluent for reconstituting research peptides, keeping multi-dose vials stable for approximately 28–30 days when refrigerated.
Overview
Bacteriostatic water (BAC water) is packaged in multi-dose vials and is specifically formulated for reconstituting parenteral (injectable) preparations. The 0.9% benzyl alcohol content inhibits microbial growth, allowing the vial to be punctured and drawn from multiple times without bacterial contamination over a 28–30 day window when stored at 2–8°C. This distinguishes it from sterile water for injection (SWFI), which is a single-use product — once the sterile vial is opened, microbial contamination risk rises with each subsequent puncture. BAC water is the overwhelmingly preferred diluent for research peptides because most protocols involve multiple doses from a single reconstituted vial over days or weeks. BAC water is available in 10 mL and 30 mL vials without a prescription in the US.
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Frequently asked questions
Where can I buy bacteriostatic water?+
BAC water is available without a prescription at pharmacies, online peptide/research supply vendors, and some compounding pharmacies in the US. It is sold in 10 mL and 30 mL multi-dose vials.
Can I use regular saline or tap water instead of BAC water?+
No. Regular saline contains no preservative and tap water is not sterile. Only use sterile preparations specifically intended for injection: bacteriostatic water or sterile water for injection.
How long does BAC water itself last after opening?+
BAC water vials are typically stable for 28 days after first puncture when stored at room temperature, and longer when refrigerated, per standard pharmaceutical guidelines.