3 mL vs 30 mL bac water: which vial belongs in your fridge door?
Bac water (bacteriostatic water) is sterile water with 0.9% benzyl alcohol added as a preservative, which is why a single vial can be entered more than once. Freeze-dried research peptides are usually mixed with it before lab work, and the two sizes you will run into most are 3 mL and 30 mL. Here is how they compare, and why our pick is the Hospira 30 mL. Laboratory research use only, adults 21+; nothing here is dosing or medical advice.
Snowman Research does not offer dosing information or usage guidance of any kind. Everything on this page is reference material about research products sold for laboratory research only.
| 3 mL vial | Hospira 30 mL vial | |
|---|---|---|
| Volume | 3 mL | 30 mL |
| Maker | Varies by vendor | Hospira (a Pfizer company), a pharmaceutical manufacturer |
| Cost per mL | Higher | Lower |
| Good for | One small vial, or a spare | Mixing many vials over a project |
| After first puncture | Date it; a 28-day discard window is the common rule unless the maker says otherwise[1] | Same rule: date it, and follow the label[1] |
Our pick: the Hospira 30 mL
For almost every lab, we strongly recommend the Hospira 30 mL bacteriostatic water. It comes from an established pharmaceutical manufacturer, so every vial is made to the same standard. It also works out cheaper per mL, and one vial stretches across many mixes, so you are not caught short halfway through a run.
About the free 3 mL at checkout
At checkout you can tick an optional box for a free 3 mL bac water with your order. Please know what that is: a courtesy add-on from a third-party vendor, and it is not guaranteed. We don't cover vendor water or take complaints about using another vendor's water, as our FAQ explains. It is a handy spare, but if consistency matters, reach for the Hospira 30 mL. We also stock 3 mL vials for small-volume work.
The 28-day rule, explained
The 28 days you see quoted comes from CDC injection-safety guidance for multi-dose vials: once a vial has been opened or punctured, date it and discard it within 28 days, unless the manufacturer specifies a different date, and never past the printed expiration date[1]. That clock applies to the water vial itself, not to a peptide after it has been mixed.
Handling either size
- Store it the way its label directs, away from direct light.
- Swab the stopper with alcohol before every entry.
- Write the first-puncture date on the vial.
- Discard it if it turns cloudy or shows particles.
When you need to work out a concentration, our Lab Calculator handles the arithmetic.
On our shelf
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Bacteriostatic water, 3ml vials
$5.00 USD
Quick questions
Is the free 3 mL bac water guaranteed?
No. It is an optional courtesy add-on from a third-party vendor and is not guaranteed. For the most consistent results we strongly recommend our Hospira 30 mL bacteriostatic water.
How long is bac water good after opening?
CDC guidance for multi-dose vials is to date the vial when first punctured and discard it within 28 days unless the manufacturer specifies a different date, and never after the printed expiration date.
Sources
- Preventing Unsafe Injection Practices: multi-dose vials. Centers for Disease Control and Prevention, Injection Safety. https://www.cdc.gov/injection-safety/hcp/clinical-safety/index.html
For laboratory research use only. Not for human or veterinary use, not FDA-approved, and nothing on this page is medical advice. You must be 21 or older to purchase.
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