# BAC Water vs Acetic Acid: Which Reconstitution Solvent Do You Need?
You've got your peptide vial. You've got your syringe. You reach for the water to mix it in — and then you realize: there are different kinds of water for this.
Bacterioststatic water (BAC water), acetic acid, sterile water, normal saline. Which one do you actually need? And what happens if you use the wrong one?
Here's the practical breakdown.
What Is Bacteriostatic Water (BAC Water)?
BAC water is sterile distilled water with 0.9% benzyl alcohol added as a preservative. The benzyl alcohol prevents bacterial growth, which is why you can store reconstituted peptides in a BAC water vial in the fridge for 4–6 weeks without degradation.
BAC water is the default choice for most peptides. It's widely available, inexpensive (~$5–8 for a 30mL vial on Amazon), and works for the vast majority of research peptides:
Peptides that work great with BAC water:
- BPC-157
- TB-500
- GHK-Cu
- MOTS-C
- Tesamorelin
- CJC-1295 (DAC and non-DAC)
- Ipamorelin
- Epithalon
- Selank
- Semax
- Thymosin Alpha-1
- NAD+
If your peptide isn't explicitly noted as hydrophobic, start with BAC water. It almost certainly will work.
When You Need Acetic Acid Instead
Some peptides won't dissolve properly in BAC water. These are typically hydrophobic compounds — they have molecular structures with lots of nonpolar regions, so water (which is polar) repels them.
When you add BAC water to a hydrophobic peptide and it doesn't dissolve after a few minutes of gentle rolling, the powder remains chalky or grainy. That's your signal: acetic acid is needed.
Peptides that typically need acetic acid:
- AOD-9604 (fat loss peptide, notoriously hydrophobic)
- Cardarine (GW501516 — technically not a peptide, but often grouped in peptide orders)
- Certain research compound blends with high lipophilic content
Acetic acid (glacial acetic acid, ~5% concentration in solution) is a stronger solvent and breaks down the molecular repulsion that BAC water can't overcome.
How to Use Acetic Acid
- Use a small amount of acetic acid (0.1–0.2mL per vial) mixed into your BAC water to create a ~1–2% acetic acid solution
- Add this mixture slowly to the peptide vial
- Let it sit for 2–3 minutes, then gently roll (don't shake)
- Once fully dissolved, you can use it normally — the acetic acid concentration is low enough that it won't degrade the peptide
Important: Don't use pure 100% glacial acetic acid. Always dilute it in sterile water or BAC water first. Pure acetic acid is caustic and can damage the peptide.
Acetic acid is less widely available than BAC water. PeptIQ does not list suppliers. Discuss appropriate diluents with a licensed clinician or pharmacist. Cost is similar (~$8–15) when obtained through lawful channels.
When You Need Plain Sterile Water
Rarely, some peptides cannot tolerate benzyl alcohol because it degrades them. The most notable example is:
Cerebrolysin — A neuropeptide complex used for cognitive support that degrades in the presence of benzyl alcohol. If you're using Cerebrolysin, you must use plain sterile water (no benzyl alcohol).
Other compounds that sometimes come with this constraint:
- Certain NAD+ preparations (some suppliers recommend sterile water)
- Dihexa (topical nootropic — can be mixed with sterile water + DMSO for topical application)
Plain sterile water is available on Amazon (~$5–8 for 30mL vials) and works just like BAC water except it lacks the preservative. Store reconstituted peptides in plain sterile water in the freezer (not the fridge) to prevent bacterial growth, and use within 2–3 weeks.
Quick Decision Tree
You have a peptide vial.
Is it Cerebrolysin or explicitly labeled "use sterile water"?
