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Bacteriostatic Water — What UK Researchers Need to Know

Published May 5, 2026

Bacteriostatic water (BAC water) is the standard diluent for reconstituting lyophilised research peptides. This guide explains what it is and how it differs from sterile water.

Composition

BAC water is sterile water for injection containing 0.9% benzyl alcohol as a bacteriostatic preservative. The preservative inhibits microbial growth, allowing multi-dose use for up to 28 days when refrigerated.

Sterile water vs BAC water

• Sterile water — no preservative, single use only.
• BAC water — 0.9% benzyl alcohol preservative, multi-dose use up to 28 days.

UK sourcing

UK Peptide Store supplies BAC water as a research accessory alongside peptide vials.

Storage

Refrigerate after first use. Discard after 28 days even if water remains.