Bac water 30ml is a multi-dose vial of bacteriostatic water with 0.9% benzyl alcohol. Learn how to use it, store it, and where to buy it safely.
A bac water 30ml vial is a 30-milliliter bottle of bacteriostatic water, which is sterile water preserved with 0.9% benzyl alcohol. It is the largest standard multi-dose size sold by Hospira (Pfizer) and by research-chemical suppliers, so it is commonly used to reconstitute freeze-dried powders and dilute solutions that need to stay sterile across many withdrawals. The preservative does not sterilize the liquid; it simply slows bacterial growth so one vial can be punctured repeatedly.
What Bacteriostatic Water Actually Is
If you are trying to pin down what is bac water, the short answer is sterile water plus a preservative. Bacteriostatic water contains 0.9% benzyl alcohol, which inhibits the growth of most bacteria and fungi that might enter the vial during repeated use. Plain sterile water and normal saline contain no preservative and are intended for single use only.
Because of the preservative, bacteriostatic water is labeled as a multi-dose diluent. It is not a medication, it does not treat any condition, and it should never be used as a substitute for IV fluids.
| Diluent | Preservative | Typical use | Multi-dose safe? |
|---|---|---|---|
| Bacteriostatic water | 0.9% benzyl alcohol | Reconstituting powders, diluting solutions | Yes, with a 28-day discard rule |
| Sterile water for injection | None | Single-use dilution, IV preparation | No |
| 0.9% sodium chloride (saline) | None | IV fluids, flushing lines | No |
| Bacteriostatic sodium chloride | 0.9% benzyl alcohol | Multi-dose dilution of compatible drugs | Yes, with a 28-day discard rule |
Why the 30 mL Size Exists
The 30 mL vial is the bulk format. It offers the lowest cost per milliliter and enough volume to reconstitute several batches before the vial is emptied.
- Lower cost per mL than 3 mL or 10 mL vials
- Fewer vials to buy, label, and store
- Enough volume for repeated reconstitution over several weeks
- Standard sealed packaging with a rubber stopper and flip-off cap
Smaller sizes still make sense for low-volume users. Someone reconstituting a single small vial every few weeks is usually better served by bac water 3ml, while a lab or a high-frequency protocol benefits from the 30 mL format.
| Vial size | Approximate US price | Best for | Cost per mL |
|---|---|---|---|
| 3 mL | $4–$8 | Single protocol, travel, very small batches | Highest |
| 10 mL | $6–$12 | Occasional reconstitution, one or two vials at a time | Moderate |
| 30 mL | $10–$20 | Frequent reconstitution, labs, multi-vial protocols | Lowest |
How to Reconstitute With Bac Water 30ml
The process is the same regardless of vial size, but the larger bottle means more punctures over time, so technique matters.
- Swab the stopper of both vials with alcohol and let it air dry.
- Draw the volume of bac water for injection you need with a new, sterile syringe and needle.
- Inject the water slowly against the inside wall of the powder vial instead of directly onto the powder.
- Swirl gently rather than shaking, because foam and shear can damage fragile proteins.
- Label the vial with the date, the concentration, and the volume you added.
A quick example: adding 5 mL of bacteriostatic water to a 5 mg powder produces 1 mg/mL, or 1,000 mcg/mL. Adding 10 mL to the same 5 mg produces 0.5 mg/mL, which makes very small doses easier to measure accurately.
Matching volume to dose
More diluent does not change the total amount of powder; it only changes the concentration. Choose the volume that gives you a syringe reading you can measure reliably, then stay consistent with that same ratio for the life of the vial.
Storage and Shelf Life
Unopened bacteriostatic water 30ml vials should be stored at controlled room temperature, away from light, and never frozen. Freezing can crack the glass or push the stopper loose and break the seal. Once a vial has been punctured, most pharmacies follow a 28-day discard rule even though the liquid may still look perfectly clear.
Inspect the solution before every use. Cloudiness, floating particles, or any change in color means the vial should be discarded immediately, regardless of what the expiration date says.
Where to Buy Bac Water 30ml
In the United States, bacteriostatic water is sold by hospital and compounding pharmacies, medical distributors, and research-chemical suppliers that label the product for laboratory use only. Availability varies by state and by store, so it is worth checking where can you buy bac water before you commit to a protocol that depends on it.
Retail chain drugstores are hit or miss. Walgreens and similar chains rarely keep bacteriostatic water on the open shelf because it is treated as a pharmacy item, and many locations will only order it with a prescription or a documented professional account. Compounding pharmacies and licensed medical suppliers are generally more reliable sources.
If your goal is peptide work, quality matters more than price. The best bac water for peptides arrives in a sealed, labeled vial from a licensed manufacturer with a verifiable lot number and expiration date, not an unlabeled bottle from a marketplace seller.
Safety and Legal Limits
Bacteriostatic water is an FDA-approved diluent for injectable drugs, but that approval covers its use as a diluent, not the reconstitution of unapproved or research-only compounds. Benzyl alcohol is not safe for neonates and should never be used for large-volume IV replacement.
Anyone using bacteriostatic water for a personal protocol should speak with a licensed healthcare professional first, especially when pregnant, nursing, or taking prescription medication. Sterile technique, single-use needles, and proper sharps disposal matter more than the brand printed on the vial.
Frequently Asked Questions
How long does a 30ml vial of bac water last?
An unopened vial is good until the expiration date printed on the label when stored at controlled room temperature. After the first puncture, most pharmacies follow a 28-day discard rule because the benzyl alcohol preservative slows but does not eliminate bacterial growth. Discard the vial sooner if the solution turns cloudy or contains particles.
Can I buy bac water at Walgreens?
Usually not off the shelf. Walgreens and other chain drugstores generally treat bacteriostatic water as a pharmacy-only item and may require a prescription or a professional account before ordering it. Compounding pharmacies, hospital suppliers, and licensed medical distributors are more dependable sources in most states.
How much bac water do I mix with a 5mg vial?
The volume depends on the concentration you want. Adding 5 mL of bacteriostatic water to a 5 mg powder gives 1 mg/mL, while adding 10 mL gives 0.5 mg/mL. Use a new sterile syringe, inject the water against the vial wall, and swirl gently instead of shaking.
This page provides educational research information and does not replace medical advice, diagnosis, or treatment.