What Does NSF/ANSI 61 Mean for GFS Potable Water Storage Tanks?

When engineers specify a storage tank for municipal drinking water, one requirement often appears near the top of the technical specification:

“Materials in contact with potable water shall comply with NSF/ANSI/CAN 61.”

For buyers evaluating GFS potable water storage tanks, this requirement is important—but it is also frequently misunderstood.

NSF/ANSI/CAN 61 does not simply mean that a tank is “food grade,” “safe,” “high quality,” or structurally suitable for drinking water service.

It has a much more specific purpose.

The standard establishes health-effects requirements for products, components and materials that come into contact with drinking water. In practical terms, it evaluates whether materials can contribute unacceptable levels of regulated substances or other contaminants to drinking water under defined test conditions.

That distinction matters.

A GFS tank may need to satisfy several completely different categories of project requirements:

• potable-water contact requirements;

• structural design requirements;

• coating quality requirements;

  corrosion-resistance requirements;

• wind and seismic requirements;

• leak-tightness requirements;

• installation requirements;

• local drinking-water regulations.

NSF/ANSI/CAN 61 addresses only part of this overall compliance picture.

Understanding exactly what it means helps engineers write better specifications, evaluate suppliers more accurately and avoid accepting incomplete certification claims.

1. What Is NSF/ANSI/CAN 61?

NSF/ANSI/CAN 61 is commonly titled:

Drinking Water System Components – Health Effects

Its purpose is to establish minimum requirements for evaluating the potential health effects of materials, components, products and systems that come into contact with drinking water.

NSF describes the standard as covering products and materials used within drinking-water systems and evaluating contaminants or impurities that may be imparted to the water from those materials.

This is different from evaluating whether a product:

• can support a certain structural load;

• can withstand wind;

• can withstand seismic forces;

• will last a certain number of years;

• will resist mechanical impact;

• will remain leak-free;

• will prevent microbial growth;

• improves taste or odor.

Those characteristics require other specifications, standards or engineering evaluations.

This leads to one of the most important points for tank procurement:

NSF/ANSI/CAN 61 is a drinking-water health-effects standard, not a complete tank-performance standard.

2. Why NSF/ANSI 61 Matters for Potable Water Storage Tanks

Water stored inside a tank can remain in contact with tank surfaces for hours, days or potentially longer.

That means materials used inside the tank can have prolonged contact with finished drinking water before it enters the distribution system.

Water-contact components may include:

• internal tank coating;

• sealants;

• gaskets;

• joint materials;

• fittings;

• pipes;

• valves;

• internal accessories;

• repair materials.

For a Glass-Fused-to-Steel tank, the primary water-contact barrier is normally the vitreous enamel surface fused to the steel panels.

However, the coating is not necessarily the only material contacting the stored water.

Bolted joints, sealing materials, nozzles and certain accessories may also contact the water.

Therefore, engineers should think about NSF/ANSI/CAN 61 in terms of the complete water-contact system, not merely the tank shell.

3. What Does NSF/ANSI/CAN 61 Actually Evaluate?

The main concern is whether substances can migrate or leach from a material into drinking water at levels that create unacceptable health effects.

The standard includes requirements for different categories of drinking-water system products.

NSF identifies categories including:

• pipes and related products;

• protective barrier materials;

• joining and sealing materials;

• process media;

• mechanical devices;

• mechanical plumbing devices.

Protective barrier materials can include coatings, while joining and sealing materials can include products such as gaskets and adhesives.

This is particularly relevant to bolted potable water tanks because a typical system combines multiple material types.

For example:

Glass-Fused-to-Steel coating
Provides the internal barrier between stored water and the steel substrate.

Tank sealant
Seals panel joints and may remain exposed to stored water.

Gaskets or sealing components
May be used around connections, manways or accessories.

Internal fittings
May include metals, elastomers or other materials.

A technically sound potable-water specification should therefore identify which of these water-contact components require documented compliance.

4. What NSF/ANSI 61 Does Not Mean

One of the biggest procurement mistakes is treating NSF/ANSI 61 as a general quality certificate.

It is not.

NSF specifically explains that the standard does not establish requirements for product performance, taste and odor, or microbial-growth support.

For GFS storage tanks, this means NSF/ANSI/CAN 61 certification alone does not prove:

Structural Strength

It does not tell you whether the tank shell is designed for the required hydrostatic pressure.

Wind Resistance

It does not establish whether the tank can withstand project wind loads.

Seismic Resistance

It does not confirm that tank anchorage is appropriate for the seismic conditions of the site.

Coating Durability

It does not, by itself, establish how long the enamel coating will perform in service.

Leak Tightness

It does not confirm that bolted joints have been installed correctly.

Tank Capacity

It does not validate whether the tank provides the required usable storage volume.

Hydraulic Performance

It does not tell you whether inlet, outlet or overflow systems are correctly sized.

Water Turnover

It does not prove that the tank avoids excessive water age.

Microbial Control

It should not be interpreted as proof that bacteria, biofilm or algae can never develop in a storage system.

This distinction is essential when reviewing a supplier's marketing statements.

“NSF/ANSI 61 compliant” should answer a specific potable-water material question.

It should not be used as a substitute for the rest of the engineering specification.

5. NSF/ANSI 61 vs. Structural Tank Standards

Another common source of confusion is the relationship between NSF/ANSI/CAN 61 and tank structural standards.

They serve different purposes.

A simplified comparison is:

For factory-coated bolted steel water storage tanks, projects may separately specify structural requirements such as AWWA D103 or another applicable national, regional or project standard.

NSF/ANSI/CAN 61 does not replace those structural requirements.

A potable-water tank may therefore need to satisfy both:

health-effects requirements for water-contact materials

and

engineering requirements for the physical tank structure.

One should never be assumed to prove the other.

6. Which Parts of a GFS Tank Should Engineers Review?

When reviewing a GFS potable water tank submittal, engineers should identify every component that can reasonably contact stored water.

6.1 Internal Glass-Fused-to-Steel Surface

The enamel coating forms the main water-contact surface across the shell.

The engineer should confirm the applicable certification scope for the proposed coating system rather than relying only on a generic statement that “GFS is suitable for potable water.”

Different coating formulations or production systems should not automatically be assumed to have identical certification status.

6.2 Joint Sealant

Bolted GFS tanks depend on sealant between panel joints.

This material is particularly important because it may remain continuously exposed to potable water.

The specification should identify:

• sealant manufacturer;

• product designation;

• potable-water suitability;

• applicable certification;

• application requirements.

6.3 Gaskets

Gaskets may be used in connections, valves, manways or other interfaces.

If they contact potable water, their suitability should be evaluated.

6.4 Pipe Connections

Nozzles and internal piping components may introduce additional materials into the water-contact system.

6.5 Repair Materials

This is often overlooked.

If coating damage occurs during transport or installation and an approved repair material is used on an internal surface, engineers should verify whether that repair system is appropriate for potable-water contact.

Using a certified tank coating but an unsuitable field repair material creates an obvious gap in the intended compliance chain.

7. “NSF Tested” and “NSF Certified” Are Not Automatically the Same Claim

Procurement documents should use precise wording.

There can be an important difference between statements such as:

• tested according to NSF/ANSI/CAN 61;

• meets NSF/ANSI/CAN 61 requirements;

• material complies with NSF/ANSI/CAN 61;

• product certified to NSF/ANSI/CAN 61;

• NSF-listed product.

NSF explains that testing and certification requirements may vary depending on the applicable product and market requirements. Third-party certification involves more than simply performing one laboratory test.

For important municipal projects, buyers should not stop at a supplier's brochure.

Ask for the actual certification information.

8. How to Verify an NSF/ANSI 61 Claim

A strong technical evaluation should follow several steps.

Step 1: Request the Certificate

Ask the supplier to provide current certification documentation.

Check:

• company name;

• manufacturing location;

• product or material designation;

• relevant standard;

• certification status.

Step 2: Identify What Is Actually Certified

This is critical.

Does the certification cover:

• a coating material?

• a sealant?

• a specific tank product?

• a product family?

• a mechanical component?

Do not assume that certification of one component automatically certifies every component in the finished tank.

Step 3: Check the Official Listing

Where third-party NSF certification is specified, engineers can verify relevant products through current official listings.

NSF's listing pages explicitly note that, unless otherwise indicated, certification for materials may apply only to the identified water-contact material.

This is precisely why buyers should review the listing details rather than treating an NSF logo as sufficient evidence.

Step 4: Check Limitations

Certification listings may contain conditions such as:

• product dimensions;

• water-contact temperature;

• material designation;

• application conditions;

• specific model numbers;

• other limitations.

These details matter.

Step 5: Confirm the Proposed Product Matches the Listing

The tank offered in the quotation should use the same certified material or system referenced in the documentation.

Substitutions should be reviewed before approval.

9. Why the Certification Scope Matters

Consider a hypothetical supplier offering a potable-water GFS tank.

The quotation states:

“NSF 61 Certified.”

That sounds reassuring, but it raises several questions:

• Is the GFS enamel coating certified?

• Is only the sealant certified?

• Is the entire tank product included?

• Which manufacturing facility is covered?

• Is the exact coating formulation covered?

• Are the proposed repair materials covered?

• Are there temperature or size restrictions?

If the certification applies only to one joining material, it should not be presented as evidence that every water-contact component of the tank has been evaluated.

The correct approach is:

claim only what the certification scope actually supports.

This is an important principle not only for regulatory compliance but also for technical procurement accuracy.

10. NSF/ANSI/CAN 61 Does Not Replace Water Chemistry Review

Another misconception is that NSF/ANSI/CAN 61 certification means a material is suitable for every possible water chemistry.

That conclusion is too broad.

NSF/ANSI/CAN 61 addresses health effects associated with substances imparted into drinking water.

Engineering material compatibility remains a separate consideration.

For example, the tank designer may still need information about:

• water pH;

• chloride concentration;

• sulfate concentration;

• disinfectant type;

• disinfectant concentration;

• temperature;

• conductivity;

• other treatment chemicals.

Why?

Because material suitability involves both:

what the material may release into the water

and

how the stored water may affect the material.

These are not the same engineering question.

For unusual water chemistry, corrosion and compatibility should therefore be evaluated independently of NSF/ANSI/CAN 61 status.

11. NSF/ANSI/CAN 61 vs. NSF/ANSI/CAN 372

Buyers may also encounter NSF/ANSI/CAN 372.

The two standards should not be confused.

NSF/ANSI/CAN 372 specifically addresses lead content and provides a standardized methodology for evaluating compliance with lead-content requirements.

NSF explains that 372 addresses lead content only, while NSF/ANSI/CAN 61 is generally used to evaluate health effects associated with substances extracted or leached from drinking-water system products.

A simplified comparison is:

Depending on the product, jurisdiction and project requirements, both may be relevant.

Again, neither should be interpreted as a complete structural tank standard.

12. What Should an Engineer Write in the Tank Specification?

Avoid vague wording such as:

“Tank must be food grade.”

or:

“Tank must be safe for drinking water.”

These phrases are difficult to verify.

A stronger specification could state that:

All specified materials in direct contact with potable water shall comply with the drinking-water health-effects requirements applicable to the project, including NSF/ANSI/CAN 61 where required by the authority having jurisdiction. The supplier shall submit current third-party certification or listing documentation identifying the covered product or material and any applicable limitations.

The specification should then separately define:

• structural standard;

• tank capacity;

• coating requirements;

• design loads;

• sealant requirements;

• roof;

• fittings;

• testing;

• installation;

• commissioning.

This prevents one certification from being used to imply compliance with unrelated technical requirements.

13. What Documentation Should Procurement Teams Request?

A municipal or EPC procurement package should request enough evidence to verify the proposed potable-water system.

Useful documentation may include:

NSF/ANSI/CAN 61 Certificate or Listing

Confirm the current certification scope.

Product Designation

The quotation should clearly identify the product, coating or material being supplied.

Technical Data Sheet

Check that the technical data corresponds to the certified product.

Sealant Data

Confirm potable-water suitability for joint materials.

Repair Material Documentation

Verify materials used for internal coating repairs.

Manufacturing Facility Information

Where relevant to certification, confirm the proposed product is manufactured at an approved facility.

Quality Documentation

Request appropriate factory quality-control records.

Installation Procedure

Potable-water-safe materials can still be improperly installed.

Commissioning Procedure

Cleaning and disinfection requirements should be separately defined according to the project and local authority.

14. A Practical Supplier Evaluation Example

Assume three suppliers quote the same 2,000 m³ municipal potable-water tank.

Supplier A

Quotation states:

“Potable Water Quality Tank.”

No defined standard is provided.

Evaluation: Insufficient.

Supplier B

Quotation states:

“Materials tested to NSF 61.”

A laboratory test report for one coating sample is provided.

Evaluation: Better, but the engineer should confirm whether certification is required and what other water-contact materials are used.

Supplier C

Provides:

• applicable NSF/ANSI/CAN 61 certification documentation;

• product or material designation;

• certification scope;

• sealant documentation;

• coating data;

• structural calculations;

• tank drawings;

• installation procedures.

Evaluation: Easier to verify technically because the evidence is traceable.

Notice that the evaluation is not simply:

Certified = good

and

not certified = bad.

The actual requirement depends on the project and jurisdiction.

The engineering objective is to establish a clear chain between:

project requirement → offered material → certification evidence → installed tank.

15. Common NSF/ANSI 61 Procurement Mistakes

Mistake 1: Treating “Food Grade” as Equivalent to NSF/ANSI/CAN 61

“Food grade” is too broad unless a specific applicable standard is identified.

Mistake 2: Looking Only at the Tank Coating

Sealants, gaskets and other internal components may also contact potable water.

Mistake 3: Accepting a Logo Without Documentation

A certification mark should lead to verifiable product information.

Mistake 4: Assuming One Certified Material Covers the Entire Tank

Certification scope must be checked.

Mistake 5: Ignoring Product Designations

The material supplied should match the material described in the certification documentation.

Mistake 6: Ignoring Certification Limitations

Temperature, size, use conditions or other restrictions may apply.

Mistake 7: Using NSF/ANSI/CAN 61 as a Structural Standard

Potable-water health-effects compliance does not establish wind, seismic or hydrostatic design adequacy.

Mistake 8: Ignoring Field Repair Materials

Any material added to the internal water-contact surface should be reviewed.

Mistake 9: Forgetting Installation Quality

A correctly certified sealant can still perform poorly if it is improperly applied.

Mistake 10: Assuming Certification Eliminates the Need for Commissioning

The completed tank still requires appropriate inspection, cleaning, testing and potable-water commissioning.

16. NSF/ANSI 61 Review Checklist for GFS Potable Water Tanks

Before approving a potable water tank supplier, engineers and procurement teams can use the following checklist.

This checklist helps prevent certification review from becoming a simple document-collection exercise.

17. What Should EPC Contractors Check Before Tank Approval?

EPC contractors usually have responsibility for integrating multiple packages.

For the tank package, the review should connect:

material compliance

with

engineering compliance.

A practical approval process could include:

Stage 1 – Technical Bid Evaluation

Check whether NSF/ANSI/CAN 61 requirements are clearly addressed.

Stage 2 – Document Review

Verify certificates, listings and product designations.

Stage 3 – Drawing Review

Confirm all internal materials and connections.

Stage 4 – Production Approval

Ensure approved materials are used during manufacturing.

Stage 5 – Site Inspection

Check that no unapproved substitutions are introduced during erection.

Stage 6 – Commissioning

Verify cleaning, testing and disinfection according to project requirements.

This is especially important on international projects where the engineering consultant, EPC contractor, tank manufacturer and installation contractor may all be different companies.

18. Does NSF/ANSI 61 Guarantee Drinking Water Will Remain Safe?

No single tank-material certification can guarantee final drinking-water quality.

Water quality in storage depends on many additional factors, including:

• incoming water quality;

• disinfectant residual;

• tank turnover;

• temperature;

• hydraulic mixing;

• contamination control;

• maintenance;

• roof integrity;

• vent protection;

• cleaning;

• distribution-system conditions.

NSF/ANSI/CAN 61 addresses the health-effects contribution from water-contact products and materials.

It does not replace good drinking-water system design and operation.

A potable-water tank should therefore be designed as part of the complete water distribution system.

19. Is NSF/ANSI 61 Required Everywhere?

Requirements vary by country, state, municipality, water authority and project specification.

NSF notes that many U.S. drinking-water regulations require third-party certification of drinking-water system components to NSF/ANSI/CAN 61, but the exact legal or contractual requirement should always be checked for the project location.

International projects may instead reference:

• NSF/ANSI/CAN standards;

• national drinking-water standards;

• regional approvals;

• utility-specific requirements;

• client specifications.

Therefore, a buyer should not automatically copy a U.S.-based specification into every international tender.

Start with:

What does the authority having jurisdiction require?

Then specify the appropriate evidence.

20. Questions to Ask a GFS Potable Water Tank Supplier

Before approving a tank for drinking-water service, ask the supplier:

1. What NSF/ANSI/CAN 61 certification applies to the proposed tank or water-contact materials?

2. Can you provide the current certification documentation?

3. What exact product designation appears in the certification?

4. Does the certification apply to the internal GFS coating?

5. What sealant is used between the bolted panels?

6. Is the sealant approved for the required potable-water application?

7. What other materials contact the stored water?

8. Are internal coating repair materials suitable for drinking-water contact?

9. Are there any temperature or application limitations?

10. Does the proposed manufacturing facility correspond to the certification documentation where required?

11. Which structural standard is used for tank design?

12. What quality-control tests are performed on GFS panels?

13. How is coating damage identified before erection?

14. What repair procedure is used?

15. How is tank leak testing performed?

16. What documentation is supplied at project handover?

A capable supplier should be able to answer these questions clearly rather than relying on one certification logo.

Frequently Asked Questions

What does NSF/ANSI/CAN 61 mean for a potable water tank?

It means that applicable products, components or materials have been evaluated against health-effects requirements related to substances potentially imparted into drinking water. The exact certification scope should always be checked.

Does NSF/ANSI/CAN 61 certify the structural strength of a GFS tank?

No. Structural strength, hydrostatic loading, wind loading, seismic design and anchorage must be addressed separately through the applicable engineering standards and project design.

Is NSF/ANSI/CAN 61 the same as food-grade certification?

No. “Food grade” is a broad description and should not be treated as equivalent to compliance with a defined potable-water standard.

Does every component in an NSF-certified tank automatically have NSF/ANSI/CAN 61 certification?

Not necessarily. Certification scope varies. Engineers should verify exactly which product, system or water-contact material is covered.

Should the tank sealant also be reviewed?

Yes. Sealant between bolted panels may contact stored water continuously, making its potable-water suitability an important part of tank evaluation.

Is NSF/ANSI/CAN 372 the same as NSF/ANSI/CAN 61?

No. NSF/ANSI/CAN 372 addresses lead content, while NSF/ANSI/CAN 61 evaluates health effects associated with substances potentially imparted into drinking water.

Does NSF/ANSI/CAN 61 guarantee that bacteria cannot grow inside a water tank?

No. NSF explicitly distinguishes the standard from microbial-growth performance requirements. Water age, mixing, sanitation, maintenance and system operation must be managed separately.

How can buyers verify an NSF certification?

Request current certification documentation and check the relevant official certification listing. Confirm the product designation, certification holder, scope and any stated limitations.

Final Perspective: Certification Is Evidence, Not a Substitute for Engineering

For municipal drinking-water projects, NSF/ANSI/CAN 61 is an important requirement because it provides a defined framework for evaluating the health-effects implications of materials that contact potable water.

But engineers should use it precisely.

It does not mean:

“This tank meets every requirement for potable water storage.”

It means that the products or materials within the documented certification scope have been evaluated against specific drinking-water health-effects criteria.

A complete GFS potable water tank evaluation should therefore combine:

potable-water material compliance + structural design + coating quality + sealing system + hydraulic design + installation quality + commissioning requirements.

When reviewing bids, the best approach is not simply to ask:

“Do you have NSF 61?”

Ask instead:

“What exactly is certified, can I verify it, does it match the material you are supplying, and does the rest of the tank meet the project specification?”

That question leads to a much stronger technical procurement decision.

For municipal and industrial drinking-water projects, Wansheng supplies GFS potable water storage tank solutions with NSF61-certified enameled tank products, supported by tank design, manufacturing, installation guidance and project delivery. Contact Wansheng with your required capacity, project location and potable-water compliance requirements to evaluate a suitable GFS storage tank solution.