What Is BAC Water? Bacteriostatic Water Explained

BAC water, short for bacteriostatic water, is a preserved aqueous solution commonly encountered in laboratory and research environments. A common formulation contains 0.9% benzyl alcohol, equivalent to approximately 9 mg/mL, which acts as a bacteriostatic preservative.

BAC water is also sometimes described broadly as a reconstitution solution or laboratory diluent. However, not every reconstitution solution has the same composition, so researchers should always review the specifications of the individual product.

This guide explains what BAC water is, what bacteriostatic water contains, how benzyl alcohol functions, how BAC water compares with other laboratory solutions, storage considerations, expiration, and common terminology.

Research Use Only: This article is provided for laboratory research and educational purposes. ReGene Sciences research products are not intended for human or animal consumption, medical treatment, diagnosis, or therapeutic use.

What Is BAC Water?

BAC water is an abbreviation commonly used for bacteriostatic water.

The word bacteriostatic refers to the ability of a substance to inhibit the growth or reproduction of certain bacteria.

A common bacteriostatic-water formulation contains:

The benzyl alcohol functions as the bacteriostatic preservative.

Researchers should evaluate the actual formulation and specifications of a particular product rather than assuming that every product described online as “BAC water” is identical.

What Is Bacteriostatic Water?

Bacteriostatic water is a preserved aqueous solution.

One well-established formulation contains 0.9% benzyl alcohol as a preservative. FDA-listed Bacteriostatic Water for Injection, USP products, for example, include formulations containing 0.9% or 9 mg/mL benzyl alcohol.

For laboratory research, the composition of a solution is important because the presence of a preservative distinguishes bacteriostatic water from unpreserved aqueous solutions.

BAC water and bacteriostatic water are therefore generally used as synonymous terms.

What Does BAC Stand for in BAC Water?

In the phrase BAC water, “BAC” is commonly used as shorthand for bacteriostatic.

Therefore:

BAC Water = Bacteriostatic Water

The abbreviation makes the product easier to refer to, but researchers should use the complete product composition and specifications when determining suitability for a laboratory procedure.

What Is in BAC Water?

A common BAC water formulation consists primarily of water containing 0.9% benzyl alcohol.

At 0.9% w/v, the solution contains approximately:

9 mg benzyl alcohol per mL

Benzyl alcohol has the following chemical properties:

Chemical Name: Benzyl Alcohol
Chemical Formula: C₇H₈O
Molecular Weight: 108.14 g/mol
CAS Number: 100-51-6

Water has the following properties:

Chemical Formula: H₂O
Molecular Weight: 18.02 g/mol
CAS Number: 7732-18-5

These molecular weights are properties of the individual compounds and do not change based on the size of the BAC water container.

What Is 0.9% Benzyl Alcohol?

0.9% benzyl alcohol means that the solution contains approximately 9 mg of benzyl alcohol per mL.

For BAC water containing the same 0.9% concentration, increasing the vial size increases the total amount of benzyl alcohol but does not change its concentration.

BAC Water Size Benzyl Alcohol Concentration Approx. Total Benzyl Alcohol
3 mL 9 mg/mL 27 mg
10 mL 9 mg/mL 90 mg
30 mL 9 mg/mL 270 mg

Therefore, a 3 mL and 30 mL BAC water product can have the same 0.9% benzyl alcohol concentration even though the larger container contains ten times as much total solution.

Why Does BAC Water Contain Benzyl Alcohol?

Benzyl alcohol functions as a bacteriostatic preservative.

A bacteriostatic substance inhibits the growth or reproduction of certain bacteria.

The presence of the preservative is one of the major characteristics that differentiates bacteriostatic water from unpreserved water formulations.

However, a bacteriostatic preservative does not eliminate the need for appropriate laboratory handling, contamination-control procedures, storage, or product-integrity checks.

Is BAC Water the Same as Bacteriostatic Water?

Yes. BAC water is commonly used as an abbreviation for bacteriostatic water.

Someone searching for:

may therefore be referring to the same general type of preserved aqueous solution.

The exact formulation should still be verified using the individual product specifications.

Is BAC Water the Same as Reconstitution Solution?

Not necessarily.

Reconstitution solution is a broader term describing a liquid used in a laboratory reconstitution process.

Bacteriostatic water may serve as a type of reconstitution solution when specified by an established research protocol, but not every reconstitution solution contains benzyl alcohol or has the same composition as BAC water.

In simple terms:

BAC Water → A specific preserved aqueous formulation

Reconstitution Solution → A broader category of laboratory solutions

Researchers should select materials based on composition and protocol requirements rather than relying solely on the product name.

BAC Water vs Sterile Water: What’s the Difference?

Bacteriostatic water and unpreserved sterile water are different formulations.

The primary compositional difference is the presence of a bacteriostatic preservative.

A typical 0.9% BAC water formulation contains approximately 9 mg/mL benzyl alcohol.

An unpreserved sterile-water formulation does not contain that benzyl alcohol preservative.

Because the formulations differ, the terms should not automatically be treated as interchangeable.

BAC Water vs Saline

BAC water and saline are also chemically different solutions.

Saline contains sodium chloride at a specified concentration.

A typical bacteriostatic-water formulation consists of water containing benzyl alcohol as a preservative.

Researchers should evaluate the composition and specifications required by their established laboratory protocols before selecting a research solution.

What Is BAC Water Used for in Laboratory Research?

BAC water may be encountered in controlled laboratory environments where a compatible preserved aqueous solution is specified.

Laboratory applications can include research workflows involving:

The appropriate solvent and laboratory procedure depend upon the material being studied and the requirements of the individual research protocol.

What Is a Lyophilized Research Material?

Lyophilization, commonly called freeze-drying, is a process used to remove water from materials under controlled conditions.

The resulting dry material may offer advantages for storage, transportation, and subsequent laboratory preparation.

When a laboratory protocol calls for returning a compatible lyophilized material to a liquid state, an appropriate reconstitution solution may be specified.

Researchers should follow established procedures and material-specific technical documentation.

Does BAC Water Expire?

Yes, BAC water products can have expiration dates.

For unopened material, researchers should check the manufacturer’s assigned expiration date and storage instructions.

The presence of benzyl alcohol does not mean bacteriostatic water has an unlimited shelf life.

Laboratory inventory records can include:

This information helps maintain product traceability and appropriate inventory rotation.

How Long Does BAC Water Last?

There isn’t one universal shelf life that applies to every BAC water product.

Shelf life may depend on:

For unopened BAC water, researchers should follow the manufacturer’s printed expiration date and labeled storage requirements.

Once a container has been accessed, the manufacturer’s applicable in-use documentation and established laboratory procedures should be followed.

How Long Does BAC Water Last Unopened?

An unopened BAC water product should be evaluated according to its manufacturer-assigned expiration date.

Researchers should also confirm:

An intact seal does not mean the product has an unlimited shelf life.

How Should BAC Water Be Stored?

BAC water should be stored according to the instructions supplied with the specific product.

Storage considerations may include:

For reference, some FDA-listed 0.9% Bacteriostatic Water for Injection products specify controlled room-temperature storage of 20°C to 25°C (68°F to 77°F). Storage specifications should not automatically be transferred to a different product; always follow that product’s own labeling.

Does BAC Water Need to Be Refrigerated?

Not necessarily.

Storage requirements depend upon the individual product.

Researchers should not assume that refrigeration automatically improves stability or extends shelf life.

Instead, follow the storage temperature specified by the manufacturer.

Can BAC Water Go Bad?

BAC water can become unsuitable for laboratory research because of factors such as:

Researchers should follow their applicable laboratory SOPs when determining whether research materials should be quarantined or discarded.

What Should You Look for When Buying BAC Water for Research?

When sourcing BAC water for laboratory research, product documentation can be just as important as container size.

Consider reviewing:

Clearly Identified Composition

The concentration and preservative should be clearly stated.

Lot or Batch Number

Batch identification helps maintain product traceability.

Certificate of Analysis

Where applicable, a Certificate of Analysis (COA) can provide information associated with a particular production lot.

Storage Information

The product should clearly state its appropriate storage conditions.

Expiration Information

Expiration or shelf-life information should be available where applicable.

Container Integrity

Laboratory solutions should arrive in appropriate sealed containers without visible damage.

Common BAC Water Sizes

BAC water is available in several container volumes depending upon the supplier and research requirements.

ReGene Sciences offers multiple laboratory research formats:

3 mL BAC Water

A compact-volume bacteriostatic research solution containing 0.9% benzyl alcohol.

10 mL BAC Water

A mid-volume research format containing 0.9% benzyl alcohol.

30 mL BAC Water

A larger-volume laboratory research solution containing 0.9% benzyl alcohol.

30 mL BAC Water 3-Pack

A multi-vial format designed for laboratories requiring additional research inventory.

When the concentration remains 0.9%, changing the container size does not change the benzyl alcohol concentration.

Frequently Asked Questions About BAC Water

What is BAC water?

BAC water is a common abbreviation for bacteriostatic water, a preserved aqueous solution. A common formulation contains 0.9% benzyl alcohol.

What does BAC water stand for?

BAC water commonly refers to bacteriostatic water.

Is BAC water the same as bacteriostatic water?

Yes. BAC water is widely used as an abbreviated term for bacteriostatic water.

What is in BAC water?

A common formulation contains water with 0.9% benzyl alcohol, equivalent to approximately 9 mg/mL.

What does 0.9% benzyl alcohol mean?

It corresponds to approximately 9 mg of benzyl alcohol per mL of solution.

What is the molecular weight of benzyl alcohol?

Benzyl alcohol has a molecular weight of approximately 108.14 g/mol.

What is the molecular formula of benzyl alcohol?

The molecular formula is C₇H₈O.

What is the molecular weight of water?

Water has a molecular weight of approximately 18.02 g/mol.

Is BAC water the same as reconstitution solution?

BAC water can be a type of reconstitution solution, but “reconstitution solution” is a broader term and may describe other formulations.

Does BAC water expire?

Yes. Products may carry manufacturer-assigned expiration dates. Researchers should follow the expiration and storage information for their specific product.

How long does BAC water last unopened?

Follow the manufacturer’s printed expiration date and labeled storage requirements rather than applying a universal shelf-life estimate.

Does BAC water need to be refrigerated?

Not necessarily. Storage requirements depend on the individual product and should be determined from its labeling.

Is BAC water for human use?

ReGene Sciences research products are supplied for laboratory research use only and are not intended for human or animal consumption, medical treatment, diagnosis, or therapeutic applications.

BAC Water for Laboratory Research

ReGene Sciences supplies BAC water and bacteriostatic research solutions in multiple laboratory formats.

Available sizes include:

3 mL BAC Water
10 mL BAC Water
30 mL BAC Water
30 mL BAC Water 3-Pack

Researchers can review individual product pages for formulation, volume, storage information, and available batch documentation.

All ReGene Sciences products designated for research use are supplied strictly for laboratory research purposes only.

Final Thoughts: Understanding BAC Water

BAC water, or bacteriostatic water, is a preserved aqueous solution commonly formulated with 0.9% benzyl alcohol.

The benzyl alcohol functions as a bacteriostatic preservative, distinguishing BAC water from unpreserved water formulations.

When evaluating bacteriostatic water for laboratory research, researchers should consider the product’s composition, concentration, container size, storage requirements, expiration information, batch identification, and available analytical documentation.

Because BAC water, bacteriostatic water, and reconstitution solution are sometimes used interchangeably online even though they do not always describe identical formulations, reviewing the actual product specifications is essential.