For lab reconstitution, choose a bacteriostatic water vial size by how many milliliters you use before an opened vial reaches its discard window: a 10 mL bac water vial wastes less at up to roughly 20 mL of monthly use, while a 30 mL vial is the better fit above that. The lower price per mL of a large vial only pays off if you actually use it.
How is this different from choosing a solvent volume?
The companion guide, choosing a solvent volume, is about how much solvent to add to one peptide vial to reach a target concentration. This guide is about the purchase decision one step earlier: which bottle size to stock, how much of it you will realistically use, and how many times you will pierce the closure doing so. For the full picture of what is in the bottle, see the bacteriostatic water for peptides guide.
What do the sizes cost per mL?
Reconstitution Solution is listed in four sizes. Prices below were listed on 20 October 2026 and can change, so check the product page.
| Vial size | Listed price | Price per mL |
|---|---|---|
| 3 mL | $5.50 | $1.83 |
| 5 mL | $8.95 | $1.79 |
| 10 mL | $12.50 | $1.25 |
| 30 mL | $28.00 | $0.93 |
How does the discard window change the math?
An unopened vial carries no post-puncture clock. Once it is pierced, many labs apply a discard window (28 days is a common convention for multi-withdrawal vials; follow your SOP or the supplier's label). Any volume left at the end of the window is waste. So the real cost of a vial is its price divided by the milliliters you use, not by the milliliters it holds. Buying 10 mL vials and opening them one at a time keeps the clock running on only one vial at once.
Which size wins at different monthly volumes?
| Solvent used in 28 days | Best option | Cost | Leftover |
|---|---|---|---|
| 3 mL | One 3 mL vial | $5.50 | 0 mL |
| 6 mL | Two 3 mL vials (one 10 mL costs $12.50 and leaves 4 mL) | $11.00 | 0 mL |
| 10 mL | One 10 mL vial | $12.50 | 0 mL |
| 12 mL | One 10 mL plus one 3 mL | $18.00 | 1 mL |
| 20 mL | Two 10 mL vials (one 30 mL costs $28.00 and leaves 10 mL) | $25.00 | 0 mL |
| 25 mL | One 30 mL vial | $28.00 | 5 mL |
The crossover sits near 20 mL: below it, 10 mL vials (plus a 3 mL for the remainder) cost less; above it, the 30 mL vial does. A lab reconstituting six 10 mg peptide vials at 2 mL each uses 12 mL, which is the 10 mL plus 3 mL case.
What about puncture count?
Every withdrawal pierces the rubber closure. A 30 mL vial drained in 0.5 mL steps is pierced up to 60 times, while the same volume drawn from three 10 mL vials spreads the punctures across three closures. Closure wear and contamination risk rise with puncture count, which is another reason to match vial size to realistic use. Plan reconstitutions so one withdrawal serves several preparations, and wipe the closure with 70% alcohol before each entry.
Where does the 3 mL size fit?
The 3 mL vial (the "3ml" bac water search) suits low monthly volumes and one-off reconstitutions, where leftover volume is the main cost. Storage conditions for any size are covered in storing bacteriostatic water before and after opening.
Related research guides
- Reconstitution-solution buyer's guide
- Sourcing reconstitution solvents
- Peptide concentration and reconstitution math
Research-use note
All materials discussed are supplied for in vitro laboratory research use only, and are not for human or animal use.
