Both are laboratory diluents. The difference is one ingredient — a preservative — and it decides whether a vial can be entered more than once. For laboratory research use only.
The short answer
Sterile water is purified water with no preservative. Once the stopper is entered there is nothing inhibiting microbial growth, so it is generally treated as single use.
Bacteriostatic water is sterile water containing a small amount of preservative, conventionally 0.9% benzyl alcohol. The preservative inhibits bacterial growth, which is what allows a vial to be entered multiple times across a working period.
Why it matters for lyophilized peptides
A reconstituted peptide vial is rarely consumed in a single step. Because bacteriostatic water tolerates repeated entry, it is the usual diluent for the lyophilized vials in our vial collection — GHK-Cu, the GLOW and KLOW blends, BPC-157, NAD+ and the GLP-1, GLP-2 and GLP-3 listings.
Side by side
| Sterile water | Bacteriostatic water | |
|---|---|---|
| Preservative | None | Typically 0.9% benzyl alcohol |
| Entries per vial | Treated as single use | Multiple entries |
| Typical laboratory use | One-off preparation | Reconstituting lyophilized peptides |
Handling
Swab the stopper before each entry, draw only the volume your protocol calls for, and record how much you added to each peptide vial — that volume is what defines the concentration. See how to reconstitute a research peptide and how to store research peptides.
Always check the label on the vial you received for its exact composition and handling instructions.
Related products
Bacteriostatic Water 10 mL (BAC Water) · Research peptide vials