Bacteriostatic Water Explained for Research Laboratories

Bacteriostatic water is commonly referenced in laboratory reconstitution workflows for lyophilised research peptides. This page explains what it is, how it differs from sterile water in lab SOPs, and where it sits in a Research Use Only supply chain. It is not medical advice and is not a human injection guide.

What bacteriostatic water is

Bacteriostatic water for injection (often abbreviated BAC water in lab shorthand) is sterile water containing a bacteriostatic preservative — typically benzyl alcohol at a low percentage — intended to inhibit bacterial growth after the vial is opened. Laboratories may specify it as a diluent when reconstituting peptides under an institutional SOP.

Bacteriostatic water vs sterile water

• Sterile water — no preservative; often preferred for single-use reconstitution where leftover diluent will be discarded.
• Bacteriostatic water — contains a preservative; sometimes used when SOPs allow multi-draw from a diluent vial over a defined window.

Always follow your institution’s protocol and compound-specific notes. Compatibility, assay interference, and preservative sensitivity vary by method.

Laboratory reconstitution workflow (high level)

1. Confirm peptide identity and lot against the COA.
2. Bring lyophilised material to the temperature your SOP requires before opening.
3. Add the prescribed diluent volume under aseptic technique appropriate to your lab.
4. Swirl gently; avoid vigorous foaming unless the SOP says otherwise.
5. Label concentration, lot, date, and RUO marking; aliquot if needed.

Use the reconstitution calculator for mass ÷ volume arithmetic only.

Related products & reading

• Bacteriostatic water (research supply)
• Peptide storage & handling
• RUO / UK context