Bac Water: the complete research guide
By the OzPeptides lab team · Updated 28 Sep 2026 · 14 wordsAbout the Bac Water 10ML
Bac Water 10ML is a bacteriostatic water, 0.9% benzyl alcohol, $20.
What bacteriostatic water is
Bacteriostatic water is water for injection with 0.9% benzyl alcohol added. The benzyl alcohol inhibits bacterial growth, which is what allows a reconstituted vial to be entered repeatedly over weeks rather than once.
Sterile water contains no preservative. It is sterile at the moment it is opened and offers nothing against contamination introduced afterwards, which is why a vial reconstituted with sterile water should be treated as single-use. Over several vials that difference is a real cost, not a technicality.
It inhibits growth rather than sterilising. Wipe the stopper with alcohol before each entry and use a fresh needle every time — bacteriostatic water will not rescue a vial repeatedly entered with a used one.
How much a vial needs
There is no single correct amount, because the volume sets the concentration rather than the quantity of peptide. A 10MG vial holds 10MG whether it is reconstituted with 1ML, 2ML or 3ML — what changes is how much liquid each draw has to be.
The practical rule is to pick a volume that puts a typical draw in the middle of the syringe. A one-unit draw is hard to measure accurately, and an eighty-unit draw empties the vial quickly. Round numbers help: 10MG in 2ML gives 5MG/ML, which makes 500mcg exactly ten units on a 100-unit syringe.
Vial capacity is the other constraint — most peptide vials are 2ML or 3ML and cannot hold more than that. The reconstitution calculator does this arithmetic per product rather than generically.
When you do not need it
Pre-mixed vials and pen cartridges arrive already reconstituted, so they need no diluent at all. Bacteriostatic water is only for the plain lyophilised vial, and buying it alongside a pre-mixed order is a common and avoidable mistake.
A 10ML bottle covers several vials, depending on how much goes into each. At 2ML per vial it reconstitutes five; at 3ML, three. Unopened it is stable at room temperature for a long period.
Reconstituting without wasting the vial
Direct the diluent down the inside wall of the vial rather than straight onto the freeze-dried cake, and let it dissolve rather than forcing it. Swirl gently; never shake. Foaming is the visible sign of denatured peptide, and a peptide that has foamed has lost some fraction of what was in the vial with no way to tell how much.
Let the cake dissolve fully before drawing. Undissolved material means the concentration in the liquid is lower than the calculation assumes, and the first draws will be weaker than the last. A few minutes at room temperature usually finishes what swirling starts.
The freeze-dried cake often looks like very little, and sometimes it is barely visible. That is normal — a few milligrams of peptide occupies almost no space once the water is removed — and appearance tells you nothing about whether the vial is correctly filled. The certificate does.
Shelf life, before and after
Unopened bacteriostatic water is stable at room temperature for a long period, which is why it is the one item here that does not need refrigeration until it has been used. Once a reconstituted vial exists, that vial belongs in the refrigerator and out of light.
For most lyophilised peptides the useful window after reconstitution is measured in weeks rather than days or months. Dry and cold, the same peptide outlasts that by a wide margin, which is why mixing early rather than when needed simply spends shelf life for nothing.
Freezing a reconstituted vial is not an improvement. Freeze-thaw cycles denature peptides, and the benzyl alcohol that protects a refrigerated vial does nothing for one that has been frozen and thawed. A few compounds are shorter-lived in solution than the general rule — NAD+ hydrolyses in water, glutathione oxidises on air exposure, oxytocin carries a disulfide bridge that can be reduced — and each of those guides says so on its own page.
Ordering it with vials
Most people order bacteriostatic water alongside plain vials, because the two only make sense together. A 10ML bottle covers several vials depending on how much goes into each: at 2ML per vial it reconstitutes five, at 3ML it reconstitutes three.
If the order is pre-mixed vials or pen cartridges, no diluent is needed at all — those arrive as a solution. Adding a bottle to a pre-mixed order is the most common avoidable mistake on this page, and it is worth a moment to check which format was chosen.
Where the diluent fits in an order
Every peptide in the catalogue is sold in three formats, and the diluent belongs to exactly one of them. A plain lyophilised vial is the cheapest and keeps longest, because a freeze-dried peptide stored cold and dry outlasts the same peptide in solution by a wide margin — and it is the only format that needs bacteriostatic water. Mixed in vial and pen cartridge both arrive reconstituted.
That is the whole decision: handle the reconstitution yourself, or have it done here at no extra cost (or $5 more per vial while a sale is running). Neither affects the peptide, which is the same batch tested the same way in all three formats.
Everything we make is synthesised and tested in our own lab in Blacktown, NSW, at ≥99% HPLC purity with 0 ppm heavy metals, and the batch number on each vial resolves to its own certificate. Orders placed before the daily cut-off dispatch the same day from Sydney.
Research use only
Everything on this site, this item included, is supplied for in-vitro and laboratory research only, to buyers aged 18 and over. Nothing in the catalogue is a medicine, and with the few exceptions named in the individual guides — where a registered product of the same molecule exists — nothing here is registered in Australia.
That framing is not a disclaimer bolted on the end. It is the reason this site carries arithmetic, batch certificates and honest evidence summaries rather than dosing protocols and before-and-after photographs, and it shapes what every page on it is allowed to say.
About the Bac Water
Bac Water: bacteriostatic water with 0.9% benzyl alcohol, used to reconstitute lyophilised peptide vials.