Potable Water Storage with ACS/WRAS Certified EPDM
The safest and most durable solution for water reservoirs intended for human consumption — certified by the most demanding European regulatory bodies. Organic compound migration below 0.1 mg/L. ERSAR approved for municipal reservoirs. 20-year warranty.
The Reservoir Material Contaminates the Water You Drink
Potable water is the most regulated essential commodity in Portugal. Decree-Law 152/2017 establishes over 50 parametric values for the quality of water reaching every tap. Yet the most silent link in this safety chain is frequently the material lining the reservoir where that water is stored. Uncoated concrete, non-certified paints, conventional PVC and common mastics all release compounds into stored water — compounds that only appear in detailed chemical analyses that most operators do not perform with sufficient frequency.
- Uncoated concrete releases calcium hydroxide (Ca(OH)₂) that raises pH and alters water taste; the rough, porous concrete surface is the ideal substrate for biofilm formation, including Legionella pneumophila in hot water reservoirs
- General-purpose epoxy paints — not subject to migration testing for potable water — release film fragments and decomposition compounds into the water over 10-15 years; the owner rarely knows that the drinking water contacts uncertified material
- Conventional PVC contains 20-40% plasticisers by mass (typically phthalates, recognised endocrine disruptors); these plasticisers migrate into stored water under the effect of temperature and time — EU Regulation 2020/784 restricts DEHP to 0.1% in potable water contact materials
- Common silicone mastics and sealants contain acetoxy or oxime compounds that release acetic acid or methyl ethyl ketoxime into the water — neither compound is toxicologically neutral
- Portuguese municipal reservoirs with 30-50 year old concrete without interior lining frequently have stored water pH values of 8.5-9.5 (above the DL 152/2017 parametric value of 9.5) from alkaline leaching of aged concrete
- Contamination from reservoir material is invisible in the standard bacteriological analysis most operators perform — it is only detected in TOC (Total Organic Carbon) analyses and specific compound analyses requiring an accredited laboratory
ACS/WRAS Certified EPDM — The Only Uncompromising Option for Potable Water
ACS (Attestation de Conformité Sanitaire, France) and WRAS (Water Regulations Advisory Scheme, UK) certified EPDM is formulated specifically for contact with water intended for human consumption. Its main polymer chain — exclusively single carbon-carbon bonds — is chemically inert to water, residual disinfection chlorine (typically 0.1-0.2 mg/L) and normal potable water pH variations (6.5-9.5). It contains no plasticisers susceptible to migration. EN 12873 migration tests document TOC extraction below 0.1 mg/L — far below any regulatory threshold.
- Formulation without plasticisers, phthalates, halogenated solvents or heavy metals — chemical inertness is intrinsic to the molecular architecture, not dependent on additives that become exhausted
- EN 12873 migration tests document TOC < 0.1 mg/L — orders of magnitude below the 5 mg/L TOC parametric threshold of the European Drinking Water Directive
- Smooth, non-porous surface that structurally impedes bacterial adhesion and biofilm formation — documented 60-80% reduction in biofilm formation versus bare concrete (relevant for Legionella prevention in hot water reservoirs)
- Documented certification available for ERSAR regulatory audits and Decree-Law 152/2017 requirements transposing Directive (EU) 2020/2184
- Compatible with all disinfection systems used in potable water in Portugal: chlorination (0.1-0.5 mg/L residual), chloramines, chlorine dioxide and UV radiation
- 50+ year service life without chemical degradation — eliminating replacement costs and supply interruptions that short-lived linings entail
EPDM Benefits
Dual ACS and WRAS Certification — Europe's Most Demanding Standards
ACS (Attestation de Conformité Sanitaire) is the French certification for materials in contact with water for human consumption, recognised by ERSAR and Portuguese water managers. WRAS (Water Regulations Advisory Scheme, BS 6920) is the equivalent British standard, an international benchmark. Having both certifications is best practice — the documentation satisfies any regulatory requirement in Portugal and the European Union. Membriko provides the original certificates for each project.
Migration < 0.1 mg/L — Inviolable Water Quality
EN 12873 migration tests performed on ACS/WRAS certified EPDM document Total Organic Carbon (TOC) extraction below 0.1 mg/L under worst-case conditions (three 24-hour extractions at 23°C plus one extraction at 60°C). This value is 50 times below the indicative TOC threshold of 5 mg/L of the European Drinking Water Directive. The quality of water stored in contact with certified EPDM is not affected in any regulatory parameter throughout the entire service life.
Hygienic Anti-Biofilm Surface
The smooth (Ra < 1 µm), non-porous surface of vulcanised EPDM structurally impedes bacterial adhesion and biofilm formation — the first step in any microbiological contamination of the reservoir. Comparative studies document 60-80% reduction in biofilm formation on EPDM surfaces versus bare concrete. For hot water reservoirs where Legionella pneumophila is the dominant risk, the combination of smooth surface, inert material and service temperature up to 65°C is the best protection available.
Permanent Chemical Inertness — No Degradation in 50+ Years
Unlike coatings that progressively degrade and release compounds into water over time (epoxy paints: 5-10 years; PE cistern: 25-30 years), certified EPDM maintains its chemical inertness unchanged for 50+ years. The saturated polymer chain does not undergo hydrolysis, is not attacked by residual disinfection chlorine and contains no plasticisers susceptible to progressive migration. This permanence eliminates reapplication costs, periodic compliance analyses and supply interruptions that periodic lining replacement entails.
Zero Regulatory Cost Over Service Life
ACS/WRAS certification integrated into the membrane eliminates the need for periodic migration testing of the reservoir material — required when the material lacks current certification. For municipal reservoirs subject to ERSAR audit, Membriko's ACS/WRAS documentation satisfies requirements without additional tests. Over 50 years, the savings in testing costs, auditing and supply interruptions for lining replacement represent significant value for medium and large water management entities.
Suitable for All Potable Water Storage Systems
Membriko's ACS/WRAS certified EPDM is suitable for the entire typology of potable water reservoirs in Portugal: municipal box reservoirs (50-10,000 m³ volume), elevated concrete reservoirs, rural domestic cisterns with own water source (borehole, spring), condominium reservoirs, hotel and hospitality reservoirs, fire-fighting cisterns (when in combined system), and domestic hot water (DHW) reservoirs up to 65°C.
Technical Specifications
ACS certification
Yes — Attestation de Conformité Sanitaire (France)
WRAS certification
Yes — Water Regulations Advisory Scheme (UK, BS 6920)
Thickness (standard reservoir)
1.5 mm (EN 1849-2)
Thickness (elevated reservoir / DHW)
2.0 mm (EN 1849-2)
TOC migration (EN 12873)
< 0.1 mg/L — far below 5 mg/L parametric threshold
Water temperature (continuous)
0°C to 65°C (domestic hot water)
Supported pH range
5.5 to 9.5 (full potable water range)
Residual chlorine resistance
Up to 2 mg/L — standard disinfection without degradation (ASTM D471)
Tensile strength
≥ 9 N/mm² (EN 12311-2)
Elongation at break
≥ 300% (EN 12311-2)
Hydrostatic watertightness
Pass at 60 kPa (EN 1928 Method B)
Surface roughness
Ra < 1 µm — hygienic anti-biofilm surface
Product standard
EN 13956 / EN 13967 (as applicable)
Projected service life
50+ years (ERA/SKZ/Arrhenius)
Plasticiser-free flexibility
Yes — elasticity intrinsic to vulcanised elastomer
Installation Process
- 1
Technical Visit and Regulatory Compliance Assessment
Membriko assesses the existing or planned reservoir: type and volume, operational regime (cold or hot water, pressure, flow rate), concrete condition (cracking, efflorescence, existing biofilm), inventory of all penetrations (pipes, level probes, inspection access) and applicable regulatory regime (ERSAR, Decree-Law 152/2017, EPAL standards if applicable). Membrane thickness, required certification level and necessary accessories are defined.
- 2
Coordination with Sanitary Engineer and Design
For municipal and condominium reservoirs, Membriko coordinates with the responsible sanitary engineer to ensure compliance with Decree-Law 152/2017 and ERSAR regulations. The project includes the membrane cut layout to minimise seams, design of all singular points (ACS/WRAS certified penetration flanges, inspection covers, level probes), and the installation sequence compatible with maintaining supply where possible.
- 3
Draining, Cleaning and Concrete Inspection
Complete draining and cleaning of the reservoir with sodium hypochlorite solution at 50 mg/L (concrete disinfection before installation, per NP EN 805). Removal of biofilm, calcite deposits and previous lining residues. Concrete inspection: active crack injection with potable-water-certified hydro-expansive polyurethane resin; inactive crack filling with epoxy-based mortar; sharp edge rectification. Concrete must have minimum 28 days curing for bonded EPDM installation.
- 4
Certified EPDM Membrane Installation
Installation of ACS/WRAS certified EPDM membrane with contact adhesive certified for potable water contact. The fully adhered method is used to ensure no air pockets between membrane and concrete that could create stagnation conditions favourable to biofilm. For large reservoirs, installation starts at the floor and progresses up the walls in panels of maximum available width (15.25 m) to minimise underwater seams.
- 5
Penetrations and Singular Points with Certified Accessories
All penetrations (inlet and outlet pipes, level probes, quality sensors, inspection access) receive ACS/WRAS certified EPDM flanges with compression ring creating a hermetic seal between membrane and pipe. No mastic, silicone or non-certified sealant is used at any point of contact with potable water. This is a non-negotiable condition of Membriko for all types of human consumption water reservoirs.
- 6
Seam Quality Control
All seams between EPDM panels are executed with QuickPrime Plus primer and 150 mm QuickSeam tape certified for potable water contact. Each seam is tested with a metal probe after curing (criterion: no probe penetration). Seams are documented with photography and included in the project as-built record. For municipal reservoirs subject to audit, this record is the quality documentation satisfying ERSAR requirements.
- 7
Final Disinfection and Water Analysis
After complete installation, the reservoir is washed with potable water (minimum 3 cycles) to remove any installation process residues. Disinfection with sodium hypochlorite at 25-50 mg/L for 24 hours, followed by draining and final washing per NP EN 805. Filling with mains water and bacteriological and chemical analysis (including TOC) by an accredited laboratory before entry into service. Membriko does not declare the reservoir ready for service without a satisfactory analysis result.
- 8
Technical Dossier, ERSAR Registration and Warranty Issue
Membriko delivers the complete technical dossier: original ACS/WRAS certificates for membrane and accessories, as-built photographic record of the entire installation, water analysis results, compliance declaration signed by the responsible technician, and 20-year warranty certificate. For municipal reservoirs, the dossier includes all documents required for ERSAR registration and approval. Membriko also offers an optional periodic inspection service with technical report.
Installation Techniques
Municipal Box Reservoir — Interior EPDM ACS Liner
Standard method for rehabilitation of large-volume concrete municipal reservoirs (50-10,000 m³). ACS EPDM membrane is installed as an interior liner, lining all existing concrete and creating a new water contact surface that is completely inert and certified. The method allows rehabilitation without demolishing the existing concrete structure — only the interior surface is renewed. Suitable for reservoirs that maintain structural integrity but have lost watertightness or have concrete that leaches compounds.
Vantagens
- Rehabilitation without demolition — the existing concrete structure is maintained in full
- ACS/WRAS certification integrated — ERSAR documentation included in the process
- Compatible with continuous water quality monitoring systems
- Supply interruption period minimised — fast installation over large surfaces
Desvantagens
- Requires complete draining and supply interruption during installation
- Mandatory coordination with the water managing entity and alternative supply planning
- Concrete with active cracking must be injected before membrane installation
New-Build Domestic Cistern — ACS EPDM in Concrete
For rural homes with their own water source (borehole, spring) or new construction with potable water storage requirements, Membriko installs ACS EPDM in a new reinforced concrete cistern. This solution offers unlimited capacity (5 to 500 m³), 50+ year durability and superior water quality compared with polyethylene or fibreglass cisterns on the market.
Vantagens
- Unlimited capacity — far exceeds plastic cisterns available on the market
- 50+ year durability without replacement — very favourable life-cycle cost
- Superior water quality due to complete absence of plastic migration
- Easy integration into the concrete structure of the home — invisible buried cistern
Desvantagens
- Concrete structure construction cost higher than a pre-fabricated plastic cistern
- Requires prior analysis of the source water quality (borehole or spring)
- Cistern concrete must be fully cured (28 days) before EPDM installation
Domestic Hot Water (DHW) Reservoir — ACS EPDM at 65°C
For DHW accumulation reservoirs in high-consumption buildings (hotels, hospitals, multi-family buildings), Membriko installs ACS EPDM certified for continuous service temperature up to 65°C. This temperature is recommended for Legionella pneumophila prevention in DHW systems (at 60°C, Legionella is eliminated in under 2 minutes). The combination of smooth anti-biofilm surface and chemical inertness at 65°C is the best available protection for this application type.
Vantagens
- Certified for continuous service temperature up to 65°C — anti-Legionella safety temperature
- Smooth surface impeding biofilm formation preceding Legionella colonisation
- 50+ year durability even at elevated temperature — no degradation
Desvantagens
- Requires high-temperature immersion adhesive certified for ACS and 65°C
- Thermal expansion of concrete reservoir at 65°C must be calculated for seam dimensioning
- Penetration accessories must be equally certified for ACS and for service temperature
Comparison with Other Membranes
| Característica | EPDM | Epoxy paint for water | Certified PE cistern | GRP / fibreglass |
|---|---|---|---|---|
| Potable water certification | ACS + WRAS — dual certification, recognised by ERSAR and EU | Some products certified (verify individually) — film lasts 5-10 years | EN 12451 / ACS for small volumes — limited to pre-fabricated up to ~10 m³ | Certifiable with approved gel coat — 20-30 year durability |
| Compound migration into water | < 0.1 mg/L TOC (EN 12873) — permanent over 50+ years | Low initially — increases with film degradation over 5-10 years | Low with food-grade PE — increases with UV and temperature over time | Low with approved gel coat — residual styrene in first months of service |
| Anti-biofilm surface | Excellent — Ra < 1 µm, non-porous, 60-80% less biofilm vs bare concrete | Good while film intact — degrades and creates micro-pores conducive to biofilm | Good — but surface ageing from UV/temperature creates micro-cracks | Good with intact gel coat — cracked gel coat exposes fibres that accumulate biofilm |
| Temperature resistance (hot water) | 0°C to 65°C continuous — covers full DHW and anti-Legionella range | Typical max 50-60°C — consult product data sheet | Typical max 40-50°C — deformation at higher temperatures | Typical max 60-70°C with appropriate resin |
| Durability without rehabilitation | 50+ years — single installation for the life of the reservoir | 5-10 years — reapplication with supply interruption | 25-30 years — total reservoir replacement | 20-30 years — gel coat renewal required |
| Accumulated cost over 30 years (relative index) | 100 — single installation, no supply interruptions for maintenance | 160 — 3 reapplications with compliance analyses each cycle | 130 — full replacement after 25-30 years | 140 — gel coat renewal and possible replacement |
Performance in the Portuguese Climate
Portugal — Municipal Concrete Reservoirs Aged 30-50 Years
It is estimated that over 60% of Portuguese municipal reservoirs have concrete over 30 years old without adequate interior lining. Alkaline leaching from aged concrete raises stored water pH (frequently 8.5-9.5) and the rough surfaces of carbonated concrete are ideal biofilm substrate. ERSAR has identified the rehabilitation of concrete reservoirs as one of the water sector's priorities — ACS EPDM is the technical reference solution for this rehabilitation: no demolition, integrated regulatory certification and 50+ year service life.
Rural Portugal — Homes with Own Water Sources
Portugal has over 200,000 rural homes with their own water source (borehole or spring) and concrete cistern storage. Most of these cisterns have concrete over 20 years old, without certified lining. In calcareous soil zones (Centre) and acid soil zones (North), the chemical aggressiveness of the captured water can be significant. ACS EPDM provides a chemical barrier between water and concrete, an anti-biofilm surface, and watertightness that eliminates the infiltration losses frequent in old cisterns.
North and Centre — Reservoirs with Significant Seasonal Temperature Variation
Surface reservoirs in northern and central Portugal are subject to seasonal temperature variation of 5 to 30°C (water temperature). This variation creates contraction and expansion cycles in concrete that degrade rigid linings (epoxy paints) and cause cracking in cementitious coatings. EPDM with elongation ≥ 300% accommodates these structural movements without compromising watertightness, and maintains ACS/WRAS certification across the entire service temperature range.
Algarve and South — Reservoirs with Elevated Water Temperature
In the Algarve, the water temperature in surface reservoirs can reach 25-30°C at the height of summer — a condition favourable to Legionella growth in hot water reservoirs and for accelerating migration reactions in non-certified materials. ACS EPDM certified to 65°C (for DHW) with anti-biofilm surface is the most appropriate material for these conditions. Membriko specifies 2.0 mm thickness for reservoirs with elevated temperature.
Portugal — Hotels, Hospitals and Large Buildings with Anti-Legionella Requirements
Hotels, hospitals, care homes, public pools and large buildings with centralised domestic hot water systems have a regulatory obligation to implement Legionella prevention and control plans (Decree-Law 52/2018). ACS EPDM certified to 65°C, with anti-biofilm surface (Ra < 1 µm), is the material that best supports the thermal shock protocol at 70-80°C for 30 minutes — the emergency disinfection procedure recommended when Legionella is detected.
Frequently Asked Questions
ACS (Attestation de Conformité Sanitaire) is a French certification managed by the LHRSP (Laboratoire d'Hygiène de la Ville de Paris) that assesses the conformity of materials and products in contact with water intended for human consumption, based on the Arrêté of 29 May 1997. It is recognised by Portugal, France, Belgium and most European regulatory bodies. WRAS (Water Regulations Advisory Scheme) is the British equivalent, based on BS 6920, evaluating odour, taste, turbidity, cytotoxicity and extraction of metallic and organic compounds. Having both certifications provides the most complete possible documentation — Membriko provides both for all potable water projects.
Yes. ERSAR recognises ACS and WRAS standards as valid documentation for materials in contact with drinking water in municipal reservoirs. Decree-Law 152/2017, transposing Directive (EU) 2020/2184, requires that materials in contact with water for human consumption do not compromise its quality — ACS/WRAS certification is the technical evidence demonstrating this compliance. Membriko delivers the complete technical dossier (certificates, technical data sheets, compliance declarations) for project approval by ERSAR.
Yes. The ACS EPDM used by Membriko is certified for continuous service temperature from 0°C to 65°C in immersion — covering the full range of DHW accumulation reservoirs. This temperature includes the anti-Legionella thermal shock protocol (70°C for 30 minutes), which EPDM supports without degradation. ACS certification remains valid across the entire service temperature range.
Portuguese legislation requires annual visual inspection of all potable water reservoirs. EPDM facilitates this inspection through its smooth surface and colour contrasting with concrete, making anomalies (separations, lifting, mechanical damage) immediately visible. Membriko offers an optional annual inspection service with technical report and recommendations — relevant for municipal management entities with regulatory accountability to ERSAR.
Yes, provided the concrete maintains its structural integrity. Membriko assesses the concrete condition during the technical visit: active cracks are injected with potable-water-certified hydro-expansive polyurethane resin; inactive cracks are filled with epoxy mortar; zones of carbonated concrete with reinforcement cover loss are repaired before installation. EPDM with elongation ≥ 300% accommodates residual movements of aged concrete without compromising watertightness.
Before entry into service, Membriko performs reservoir washing (3 cycles) and disinfection with sodium hypochlorite at 25-50 mg/L for 24 hours per NP EN 805. After draining and refilling with mains water, analysis by an accredited laboratory includes: complete bacteriological analysis (total coliforms, E. coli, enterococci, Legionella for DHW), physical-chemical analysis (pH, turbidity, conductivity, TOC, nitrates, metals), and compliance analysis against all parametric values of Decree-Law 152/2017. The reservoir only enters service with a satisfactory result.
Yes, provided the existing paint is well bonded to the concrete (cross-cut adhesion test EN ISO 2409). If the paint is peeling or has widespread cavities, it must be removed by grinding or high-pressure water jetting before installation. Installing EPDM over intact epoxy paint has the advantage of preserving the existing lining as a levelling layer, reducing preparation requirements and accelerating the installation process — relevant for municipal reservoirs where minimising supply interruption time is a priority.
The base chemistry is identical — both are vulcanised EPDM. The differences lie in formulation and certification: ACS EPDM does not contain plasticisers, halogenated solvents or heavy metals in the quantities present in some roofing EPDM grades; the vulcanisation system is restricted to compounds approved by ACS/WRAS lists; the carbon black used is of the grade tested for extractables; antioxidants are selected from compounds with established safety profiles for potable water contact. Membriko never uses roofing EPDM in potable water applications — ACS/WRAS certification is a mandatory condition for all such projects.
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