Bacteriostatic Water Guide: Where to Buy in Canada, How to Use
Published: 2026-08-03 · Last updated: 2026-08-03
Bacteriostatic water is the workhorse solvent for peptide reconstitution. Most Canadian buyers spend more time looking for a source than they do actually using the stuff. This guide explains what it is, why the preservative matters, where to buy it in Canada without chasing your tail, and how to use one bottle across multiple vials without contaminating anything.
What is bacteriostatic water?
Bacteriostatic water is sterile water for injection with one added ingredient: 0.9% benzyl alcohol, a mild preservative that stops bacteria from growing in the bottle after you have punctured the seal. Nothing else. The pH is close to neutral, and the finished product is clear, colourless, and odourless.
The whole point of the preservative is that once you push a needle through the rubber stopper, the sterility of the bottle is compromised. Without benzyl alcohol, bacteria from the ambient air or the needle would start growing in the water within a day or two. With benzyl alcohol, the water stays clean enough to use for about 28 days.
This 28-day figure comes from the labeling on commercial bacteriostatic water for injection (the same product used in hospitals to dilute injectable medications). It is a manufacturer stability claim, not a rigid law of physics — but it is what the industry uses, and there is no good reason to push past it.
Why use bacteriostatic water for peptide reconstitution?
Two reasons. First, the preservative extends the shelf life of your reconstituted peptide vial in the fridge. Instead of finishing a vial in three days before it goes off, you get two to four weeks of working window depending on the peptide. That changes how many vials you can reconstitute at once and how you plan a research schedule.
Second, the pH is friendly. Most research peptides are stable in mildly acidic to neutral pH environments, and bacteriostatic water sits comfortably in that range. Using something with a very different pH (like a citrate buffer or a strong saline) can affect solubility or degrade certain sequences. Bac water is the "no drama" default.
There are edge cases. A few very hydrophobic peptides need acetic acid or DMSO to dissolve properly — the CoA or product page will tell you if that applies. For the vast majority of research peptides sold in the Canadian market, bacteriostatic water is the correct solvent, and the reconstitution basics guide assumes you are using it.
Where do I actually buy it in Canada?
This is the annoying part. Retail pharmacy availability in Canada is patchy. Some Shoppers Drug Mart locations stock it. Some Rexall stores can order it. London Drugs varies. Small independent pharmacies sometimes stock it because a compounding pharmacist keeps a supply on hand. Your best move is to call three or four pharmacies before driving anywhere.
When you call, ask specifically for "bacteriostatic water for injection, 30 mL" — that is the standard SKU. Sterile water for injection is a different product and not what you want if you need the shelf-life extension. Some pharmacists will need to check with a supplier because it is not a high-volume item.
Specialty suppliers, veterinary supply houses, and lab-supply companies also carry it. Prescott Bio stocks bacteriostatic water in the Canadian catalogue when we can source it — supply from our upstream distributor is intermittent, so check the current inventory on the peptides catalogue page rather than assuming it will always be there.
How much do I need per order?
Less than you probably think. A single 30 mL bottle reconstitutes roughly 6 to 30 vials depending on the volume you use per vial. If you reconstitute at 1 mL per vial, one bottle handles 30 vials. At 5 mL per vial (rare), one bottle handles 6.
The 28-day post-open window means buying a case of ten bottles at once only helps if you are working through them within that timeframe once opened. If you are a solo researcher who reconstitutes a couple of vials a month, one bottle at a time is fine. Larger orders make sense for a group setup or for someone working through many vials in quick succession.
For the price, bacteriostatic water is cheap compared to the peptides you are dissolving in it. Do not skimp — running out mid-reconstitution and having to wait a week for a new bottle is a bad time. Keep at least one unopened backup on the shelf.
How do I use one bottle safely across many vials?
Every puncture is a chance for contamination. Wipe the bac water bottle stopper with an alcohol swab before every draw and let it air-dry for a few seconds. Use a fresh sterile syringe every time — do not reuse needles across vials, and never draw from bac water with a needle that has already been in a peptide vial.
Keep the bottle upright and store it in the fridge between uses if you can. Refrigeration is not required for bacteriostatic water once opened, but it does not hurt. What matters more is not leaving the bottle in warm sun or on a bench near heat sources.
Track the puncture date. Write it on the bottle in permanent marker the first time you break the seal, and count 28 days forward. When you hit that date, discard whatever is left and open a fresh bottle. Old bac water with degraded preservative is a real contamination vector, not a theoretical one.
Can I substitute sterile water or saline?
Sterile water for injection is the closest substitute. It has no preservative, so any reconstituted vial you make with it needs to be used within roughly 24 to 72 hours before contamination becomes a real risk. If your research pace is fast enough to finish a vial that quickly, sterile water is a workable stand-in. Otherwise, you are creating a shelf-life problem.
Saline (0.9% sodium chloride) is not a great substitute for research peptide reconstitution. The salt content can affect solubility for some peptides and can nudge the pH in ways that matter for stability. Some clinical protocols use saline, but for benchtop research work, stick with bacteriostatic water or sterile water.
Never use tap water, bottled drinking water, or distilled water from a hardware store. These are not sterile, they have unknown mineral and microbial content, and they will ruin any peptide you dissolve in them. This should be obvious but occasionally is not.
Questions Canadian buyers ask
Is bacteriostatic water sold over the counter in Canada?
Not always. Availability at Canadian pharmacies is inconsistent — some stock it, some order it in, some cannot get it at all. It is not technically prescription-only in most provinces, but it is a specialty item and many retail pharmacies just do not carry it.
How long is bacteriostatic water good for after opening?
The label typically says 28 days after first puncture. That is the industry-standard guideline for benzyl alcohol preservative efficacy. After 28 days, discard whatever is left even if the bottle is not empty — the preservative degrades and contamination risk climbs.
Can I use sterile water instead?
You can, but only for peptides you will use up within a few days. Plain sterile water for injection has no preservative, so a reconstituted vial goes off quickly. Bacteriostatic water gives you multi-week fridge life because of the 0.9% benzyl alcohol.
Does Prescott Bio sell bacteriostatic water?
When it is in stock, yes — check the Canadian catalogue. Because of intermittent supply, availability is not guaranteed. We stock it when we can and back-order when we cannot.
Is DIY bacteriostatic water safe?
No. Attempting to mix your own by adding benzyl alcohol to sterile water is a bad idea — you cannot verify concentration, sterility, or particulate contamination without proper equipment. Buy a real sealed bottle from a real supplier.