Bacteriostatic water testing: what to check, and why it matters
Published 5 October 2026 · Updated 5 October 2026
Bacteriostatic water is sterile water with a preservative added, usually benzyl alcohol. The preservative is what lets a vial be opened more than once. A Veritalys test measures the preservative level and pH, endotoxin, and runs a sterility screen, all for €399.
What bacteriostatic water should be
A pharmaceutical bacteriostatic water label (Pfizer's, read 5 October 2026) states 0.9% benzyl alcohol, which is 9 mg per ml, and a pH of 4.5 to 7.0. It should also grow nothing in culture and carry very little endotoxin.
Those four properties are what a test checks.
What can go wrong
Too little preservative. Benzyl alcohol stops bacteria from multiplying in an opened vial. If the concentration is low, or the water is plain sterile water sold under the wrong name, it does not do that job. The water looks exactly the same either way.
Contamination. If the water was not filled in clean conditions, microbes can be present from the start.
Endotoxin. Debris from dead bacteria that survives sterilisation and filtering. Water and filling equipment are where it usually comes from.
pH out of range. A sign of a formulation or storage problem.
None of these can be seen by looking at the vial.
What the Veritalys test measures
| Result | What it tells you |
|---|---|
| Benzyl alcohol | the preservative concentration, measured, not just detected |
| pH | how acidic or alkaline the water is |
| Endotoxin | bacterial endotoxin as a number in EU per vial |
| Sterility screen | whether anything grows from the sample in culture |
All four come in one panel at €399. Janoshik sells the same three tests separately: water analysis at $145, endotoxin at $180 and sterility at $290, about €529 together.
How long it takes
About three weeks from the day the laboratory receives the vial. The sterility screen works by giving anything present time to grow, and that incubation cannot be shortened.
How to send it
Order on the bacteriostatic water page, and your reference number and posting address arrive by email within a minute. Send one sealed, unopened vial. An opened vial can pick up microbes from the air or the needle, and the result would describe your handling, not the product. Write the reference on the vial, on a slip inside and on the outside, and post it tracked.
Questions people ask
What is in bacteriostatic water?
Sterile water with a preservative, usually 0.9% benzyl alcohol. The preservative stops bacteria multiplying after the vial is opened.
How do I test bacteriostatic water?
Order the bacteriostatic water check, post one sealed vial to the laboratory, and receive a report with preservative level, pH, endotoxin and a sterility result.
How much does bacteriostatic water testing cost?
€399 at Veritalys for preservative, pH, endotoxin and sterility. The same three tests at Janoshik add up to about €529.
What is the difference between sterile water and bacteriostatic water?
Bacteriostatic water contains a preservative. Plain sterile water does not, so once opened it has no protection against bacteria that get in.
Should I send an opened vial?
No. Send a sealed vial. An opened one may have picked up microbes during use, so the result would not describe the product as supplied.
How long does the test take?
About three weeks from receipt, because the sterility culture needs time to grow.
Veritalys prices come from the live price list. Janoshik prices are from janoshik.com, read 4 October 2026, with $1 taken as €0.86. For research and quality verification only.
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