AS4020 certification appears on tank spec sheets, liner products and fittings as a kind of universal reassurance. What it specifically certifies — that a product in contact with drinking water does not leach harmful substances or otherwise degrade water quality — is narrower than the blanket assurance it is often assumed to provide.
Product contact with potable water, not the whole system
AS4020 (Testing of products for use in contact with drinking water) certifies that a specific product or material — a liner, a coating, a fitting, a sealant — meets defined criteria for chemical migration and does not introduce contaminants or unacceptable taste, odour or colour into potable water. It is a materials and product certification, not a certification of an installed system's overall safety or performance.
What it does not certify
AS4020 certification of a liner or coating product says nothing about whether that product was correctly installed, whether the tank's structural design is adequate, or whether the completed installation meets AS2304's requirements for potable water storage structures. A perfectly certified product, installed incorrectly, does not deliver a compliant tank.
A tank owner or specifier who treats "AS4020 certified" as equivalent to "fully compliant potable water tank" can miss the fact that structural adequacy, correct installation, and ongoing maintenance are all separate requirements that AS4020 does not touch. Confirming AS4020 certification on the materials used is necessary, but it is one part of a compliance picture that also depends on structural design standards and installation quality.
AS4020 answers one specific question: does this product harm drinking water quality on contact? It does not answer whether the tank was built right, sized right, or maintained right — and treating the certification as if it does is a common and consequential misreading.
| Requirement | What it covers |
|---|---|
| AS4020 certification | Materials and products in contact with drinking water do not degrade its quality |
| AS2304 (or applicable structural standard) | Structural design and construction of the potable water storage tank itself |
| Correct installation by a qualified contractor | Ensures certified products actually deliver their intended protection in service |
| Ongoing inspection and maintenance | Confirms the installation continues to protect water quality over time |
If a liner is AS4020 certified, does that mean my tank is fully compliant?
Not on its own. AS4020 certifies that the liner material itself does not adversely affect drinking water quality — it does not certify the tank's structural design, the quality of the liner's installation, or ongoing maintenance, all of which are separate requirements for a fully compliant potable water tank.
Do all fittings and coatings used in a potable tank need AS4020 certification?
Any product in direct contact with the stored drinking water should carry appropriate certification for that contact — this includes liners, internal coatings, seals and fittings. It is worth confirming certification for each product individually rather than assuming one certified component covers the whole system.
How can I confirm a product's AS4020 certification is genuine and current?
Certification should be traceable to a specific product, batch or formulation and issued by a recognised certifying body — ask the supplier or installer to provide current certification documentation rather than relying on a general claim of compliance on marketing material.
Confirming compliance on a potable water tank project? We can help make sure both the materials and the installation meet what's actually required.
Talk to us about compliance