A potable water tank is held to a different standard from every other storage tank: the water leaving it must be safe to drink, and the tank itself must not make it worse. That places requirements on material certification, design, installation and maintenance that go well beyond simply holding water. This guide sets out what “potable certified” actually means and what to demand from a manufacturer.
What Potable Certification Means
Certification is not a general claim about a company — it applies to a specific material formulation in contact with drinking water. The principal schemes:
- NSF/ANSI 61 — the North American benchmark for drinking water system components, assessing health effects from extractables. Widely requested internationally.
- WRAS approval — required in the UK for materials in contact with mains water.
- BS 6920 — British standard for the effect of non-metallic materials on water quality.
- BS EN 13280 — European specification for GRP tanks used for water supply.
- National schemes — many Gulf, ASEAN and African markets require a ministry or municipal certificate in addition to international schemes.
Always ask for the certificate that names the actual resin and panel formulation to be supplied. A company-level certificate is not evidence that the product you are buying is compliant.
Material Requirements for Potable Duty
- Food-grade resin — a resin system formulated and tested for drinking-water contact; isophthalic or a dedicated potable grade.
- Smooth, non-porous internal surface — a surface that can be cleaned and that resists biofilm. Compression-moulded SMC panels are strong here because both faces are formed against polished tooling.
- Food-grade gaskets — EPDM or PVC specified for potable contact; generic sealant is not acceptable.
- Compatible fasteners — stainless steel, or hot-dip galvanised to the appropriate standard.
- No lead or heavy-metal-containing components anywhere in the wetted path.
Design Features That Protect Water Quality
Certification covers materials; design determines whether the tank stays clean in service:
- Sealed, lockable manway — the single most important contamination barrier
- Screened vent and overflow — insect-proof, with the overflow discharging to a visible air gap, never hard-connected to a drain
- Full drainability — a sloped floor to a drain point so the tank can be emptied for cleaning
- No dead legs or stagnant zones — inlet and outlet arranged to promote turnover
- Adequate access — a manway of at least 600 mm for internal cleaning
- Insulation — keeping stored water cool limits bacterial growth, particularly in hot climates
- Opaque construction — light ingress promotes algal growth
- Smooth internal joints — no ledges or crevices where sediment and biofilm accumulate
Commissioning: The Step That Decides Everything
A certified tank can still fail its first water sample if commissioning is done badly:
- Remove all construction debris and packaging
- Clean all internal surfaces with a potable-approved method
- Rinse thoroughly
- Disinfect — commonly a 50 mg/L free chlorine dose with at least one hour contact time, following the applicable national guidance
- Drain to an approved disposal point and flush until the residual matches the supply
- Refill with potable water
- Sample for total coliforms, E. coli and total viable count at the tank and at sentinel taps
- Do not put into service until results are acceptable
- Record everything — the paperwork is what demonstrates compliance
Ongoing Requirements
Potable tanks need a written maintenance regime: annual internal inspection with photographic record, periodic cleaning and disinfection, routine checks of screens and seals, temperature monitoring where relevant, and water sampling at a frequency set by the risk assessment — more often for healthcare, food production and childcare premises. Keep a logbook; it is the first thing an inspector asks for.
Selecting Potable Water Tank Manufacturers
Evidence to request:
- Current potable certificate naming the supplied formulation
- Factory audit report or evidence of in-house manufacturing
- Batch traceability — resin, glass content, cure
- Hydrostatic type-test results
- Gasket and fastener material certificates
- References from comparable potable projects
- Commissioning and disinfection capability, or a clear method statement
Specifying a drinking water tank? Send us the volume, site conditions and the certification required in your market — we will confirm the compliant resin system, provide certificates for the actual formulation, and supply a commissioning method statement.
