Watertight Water Reservoirs for 50+ Years with EPDM Membrane
Waterproof water reservoirs of any volume and purpose — irrigation, consumption, fire-fighting, industrial process — with ACS/WRAS/KTW certified EPDM. Zero chemical migration. Permanent hydrostatic pressure resistance. 20-year warranty.
Concrete Loses Water — and Contaminates What Remains
Portugal has tens of thousands of water reservoirs — municipal, agricultural, industrial, fire-fighting — and the vast majority share the same fundamental problem: concrete without adequate elastomeric lining. Concrete is structurally reliable but intrinsically porous. A 0.2 mm shrinkage crack — completely normal in reinforced concrete — is sufficient to create a loss of 30 to 100 litres per day per linear metre of crack. In reservoirs with decades of use, cracks accumulate, the epoxy or cementitious coatings applied to seal them are degraded, and the cost in water losses, maintenance and quality failures is real and growing.
- Unlined or degraded-lining concrete loses 0.5 to 3% of stored volume per month — in a 500 m³ reservoir, that represents 75 to 450 m³/month wasted
- Epoxy paints in reservoirs delaminate in 5-10 years of permanent immersion from hydrostatic pressure cycles and level variations; delamination creates pockets between paint and concrete where water stagnates and promotes biofilm
- PVC liners for reservoirs contain 20-40% plasticisers (phthalates) that progressively migrate into stored water — unacceptable for reservoirs holding water for food crop irrigation or consumption
- Cracks in concrete reservoirs not only lose water to the outside but allow soil infiltration — particles, microorganisms and soil chemical compounds enter the stored water
- Cementitious waterproofing coatings crack with 0.3 mm movements — and reservoirs always move: differential settlement, thermal cycles and level variations create structural deformations that no rigid coating accommodates
- Periodic maintenance of reservoirs with short-lived linings requires draining, cleaning, preparation and reapplication — with direct costs and service stoppage costs that accumulate over decades
EPDM Membrane — The Definitive Solution for Water Reservoirs
EPDM is the only material that simultaneously resolves the watertightness, water quality and durability problems in reservoirs. With 400% elongation, it accommodates any crack or structural movement without compromising impermeability. With ACS/WRAS/KTW certification, it guarantees that stored water is not contaminated by the lining. With a 50+ year service life, it eliminates the maintenance and replacement cycles that consume resources and interrupt service. Membriko installs reservoirs from 1 to 10,000 m³ of any geometry and purpose — new construction or rehabilitation without demolition.
- 400% elongation accommodates concrete cracks up to 20 mm and structural movements without any watertightness loss — the same movement that cracks an epoxy coating is elastically absorbed by EPDM
- Triple ACS (France)/WRAS (UK)/KTW (Germany) certification for drinking water contact and food use — documentation available for ERSAR, fire safety certifications and food quality auditors
- Zero migration of organic compounds or heavy metals into stored water — TOC < 0.1 mg/L in EN 12873 tests, far below any regulatory threshold
- Smooth surface (Ra < 1 µm) that impedes biofilm and algae adhesion — without continuous biocide treatment, water quality is maintained mechanically
- Resistance to the full pH range of stored water: 4 to 12 — from acid rainwater to alkaline water from industrial processes
- Installation in existing reservoirs without demolition — EPDM lines the interior of existing concrete, transforming a defective structure into 50-year infrastructure with only 5-15 days of service interruption
EPDM Benefits
Preserved Water Quality — Triple ACS/WRAS/KTW Certification
Membriko's certified EPDM does not alter taste, odour, pH or chemical quality of stored water in any regulatory parameter. Triple ACS (recognised by ERSAR), WRAS (BS 6920) and KTW (German Umweltbundesamt) certification documents TOC < 0.1 mg/L in EN 12873 migration tests — far below European Directive thresholds. For drinking water, food crop irrigation or food process reservoirs, this certification is not a commercial advantage — it is a minimum technical requirement.
Permanent Watertightness with 400% Elongation
The fundamental difference between EPDM and all alternative coatings is elongation. Cured epoxy has 0-2% elongation; cementitious has 0%. EPDM has 400%. A 0.3 mm crack in concrete beneath a 1.5 mm EPDM membrane produces a local deformation of approximately 0.2% in the membrane — far below the elastic capacity. The reservoir remains watertight even as the concrete develops cracks throughout its service life.
Rehabilitation Without Demolition — Installation in Existing Structures
Membriko installs EPDM as an interior liner of existing concrete reservoirs without demolishing the structure. The only condition is that concrete maintains structural integrity — active cracks are injected before installation, the surface is prepared, and EPDM covers the interior of existing concrete. For municipal reservoirs with 30-50 year old concrete, this solution is 50-80% more economical than demolition and reconstruction, with a service interruption period of only 5 to 15 days.
Zero Maintenance for 50+ Years
Once correctly installed, EPDM requires no reapplication, repainting or treatment for 50+ years. Direct maintenance costs and indirect service stoppage costs (draining, cleaning, preparation, reapplication) are eliminated for the entire reservoir service life. For managers of municipal or agricultural reservoirs with dozens of structures, eliminating these maintenance cycles represents very significant operational savings over decades.
Full Thermal Range — 0°C to 65°C
Membriko's certified EPDM maintains integrity and water contact certification across the full service temperature range of reservoirs in Portugal: cold water reservoirs (0 to 20°C), solar pre-heated reservoirs (20 to 45°C), and domestic hot water accumulation reservoirs (up to 65°C). ACS/WRAS/KTW certification remains valid across this entire temperature range.
Anti-Biofilm Surface Without Biocides
The smooth, non-porous surface of vulcanised EPDM (Ra < 1 µm) structurally impedes bacterial adhesion and biofilm formation. Comparative studies document 60-80% less biofilm on EPDM surfaces versus bare concrete. EPDM contains no biocides — biofilm inhibition is purely mechanical (unfavourable adhesion surface), with no risk of bacterial resistance or biocide migration into stored water.
Technical Specifications
Thickness (reservoir < 100 m³)
1.5 mm (EN 1849-2)
Thickness (reservoir > 100 m³ / high pressure)
2.0 mm (EN 1849-2)
Drinking water certification
ACS (France) / WRAS (UK, BS 6920) / KTW (Germany)
TOC migration
< 0.1 mg/L (EN 12873) — below any regulatory threshold
Water temperature
0°C to 65°C (continuous)
Supported pH range
4 to 12 — full agricultural and industrial reservoir range
Residual chlorine resistance
Up to 2 mg/L — no degradation (ASTM D471)
Elongation at break
≥ 400% (EN 12311-2)
Tensile strength
≥ 9 N/mm² (EN 12311-2)
Hydrostatic watertightness
Pass at 60 kPa — equivalent to 6 m water head (EN 1928 Method B)
Surface roughness
Ra < 1 µm — anti-biofilm surface
Maximum available width
15.25 m — underwater seam minimisation
Dimensional stability
< 1% (EN 1107-2)
Product standard
EN 13956 / EN 13967 / DIN 4033
Projected service life
50+ years (ERA/SKZ/Arrhenius)
Installation Process
- 1
Technical Visit and Reservoir Structural Assessment
Membriko assesses the existing or planned reservoir: type and volume, purpose (drinking water, irrigation, fire-fighting, industrial process), geometry (rectangular, circular, irregular, L-shaped), concrete condition (cracking, efflorescence, biofilm, previous lining), penetration inventory (inlets, outlets, overflow, probes, access), and hydrostatic pressure regime. Membrane thickness (1.5 or 2.0 mm) and certification level are defined from this assessment.
- 2
Cut Layout Design and Accessory Specification
Cut layout is designed to minimise seams — in rectangular reservoirs up to 15 m wide, the floor can frequently be covered with a single panel without underwater seams. Accessory certification (flanges, compression rings) is defined according to reservoir use: ACS/WRAS/KTW for drinking and food water; fire safety certification for fire-fighting reservoirs. The project includes the installation sequence compatible with minimising service stoppage time.
- 3
Draining, Cleaning and Surface Preparation
Complete draining and high-pressure water jet cleaning (removal of biofilm, limescale deposits, non-adhering previous lining). Active crack injection with hydro-expansive polyurethane resin. Inactive crack filling with epoxy mortar. Sharp edge rectification. Flatness verification (irregularities > 5 mm corrected). For existing epoxy coatings in good condition, Membriko can install on top without removal — reducing preparation time.
- 4
EPDM Membrane Installation — Floor and Walls
Installation starts at the floor with the largest panel, bonded to 100% of the surface (fully adhered) with contact adhesive certified for water contact and for the reservoir service temperature. The fully adhered method is essential for reservoirs with elevated hydrostatic pressure: it eliminates air pockets that, under pressure, would create localised membrane lifting. After the floor, walls are lined from bottom to top with 100 mm overlap onto the floor panel.
- 5
Corners, Seams and Quality Control
Interior and exterior corners receive pre-formed EPDM pieces (90° corners). All seams are executed with QuickPrime Plus primer and 150 mm QuickSeam tape. Each seam is tested with a metal probe after curing. Seams are documented with photographs and included in the as-built record. For municipal reservoirs subject to ERSAR audit, this record satisfies installation quality control requirements.
- 6
Certified Penetrations — Pipes, Probes and Access
Each penetration (inlet and outlet pipes, overflow, floor drain, level probe, quality sensors, inspection access covers) receives an EPDM flange with compression ring creating a hermetic and certified seal. Flange certification matches the membrane: ACS/WRAS/KTW when required by use. No non-certified mastic or silicone is used as primary sealant at any point of contact with stored water.
- 7
Access Cover, Termination Bar and Reservoir Covering
The wall membrane is terminated at the coping level with a mechanical termination bar in anodised aluminium or stainless steel. The inspection and maintenance access cover is installed with a stainless ring and sealing compatible with the reservoir certification. For uncovered reservoirs, Membriko coordinates with the contractor on the installation of the cover (concrete slab, modular cover or floating cover) to prevent solar light promoting algae growth and excessive water heating.
- 8
Watertightness Test, Water Analysis and Final Documentation
The reservoir is filled with water and the level monitored for 48-72 hours. Any level drop beyond normal evaporation triggers a leak inspection. For drinking water reservoirs, Membriko performs the disinfection protocol (NP EN 805) and collects samples for bacteriological and chemical analysis before entry into service. The final technical dossier includes ACS/WRAS/KTW certificates, as-built photographic record, water analysis results and 20-year warranty certificate.
Installation Techniques
Full-Surface Bonded EPDM — New Construction
For new reinforced concrete reservoirs, Membriko installs EPDM during construction, bonded to the full interior surface after complete concrete curing (minimum 28 days). This is the highest-performance and most durable method: the membrane adheres to 100% of the surface, without air pockets, without risk of lifting from hydrostatic pressure. Suitable for all purposes and volumes from 1 to 10,000 m³.
Vantagens
- Maximum adhesion and watertightness — no air pockets that could create lifting under pressure
- Direct integration with construction sequence — no future adaptations
- ACS/WRAS/KTW certification integrated in the installation from the first day of service
- Complete technical documentation available for licensing and audit
Desvantagens
- Requires coordination with concrete contractor and respect for curing deadlines
- Access may be limited after cover or slab installation — Membriko plans the installation sequence in advance
- Concrete structure must be dry (no active moisture) before adhesive installation
Free-Lay EPDM as Interior Bag — Fast Rehabilitation
For rehabilitation of existing reservoirs where full surface preparation is not feasible or where very fast installation is required, Membriko can install EPDM as an interior "bag" fixed only at the upper perimeter with a mechanical termination bar. EPDM floats on the interior concrete surface, supported by the weight of water. Faster but less robust method than full bonding.
Vantagens
- Very fast installation — reservoir returns to service in 24-48 hours after work start
- Does not require full surface preparation — suitable for irregular concrete or unremovable old lining
- The bag accommodates structural movements without risk of localised debonding
Desvantagens
- Requires structure without excessive deformation — the bag must not have excess length that creates folds or stress concentrations
- Less stable in reservoirs with turbulent water inlet that could displace the bag
- The bag may accumulate water underneath in case of leakage — periodic inspection is more important in this system
EPDM with Field Seams — Large Agricultural Reservoirs
For large agricultural reservoirs (100 to 10,000 m³) with dimensions exceeding available membrane width (15.25 m), Membriko executes field seams on site using the QuickSeam system. This method allows dimensioning the system for any reservoir volume without a practical upper limit. Membriko trains installers specifically for field seams and verifies each seam systematically before completing installation.
Vantagens
- No practical volume limit — reservoirs of 1,000 to 10,000 m³ are installed using this method
- Field seams with strength equivalent to factory seams when correctly executed
- Suitable for large-scale irrigation reservoirs (vineyards, olive groves, orchards) with high water autonomy requirements
Desvantagens
- Requires temperatures above 5°C and no rain during seam execution
- Higher risk of error in field seams versus factory seams — Membriko supervision is mandatory
- Installation time proportional to number of field seams required
Comparison with Other Membranes
| Característica | EPDM | Interior epoxy paint | Cementitious coating | GRP/fibreglass liner |
|---|---|---|---|---|
| Structural crack and movement accommodation | Excellent — 400% elongation, accommodates cracks up to 20 mm without watertightness loss | None — 0-2% elongation; cracking inevitable with any concrete movement | Poor — cracking with 0.3-0.5 mm movements | Poor — brittle gelcoat; cracking with structural movements or impacts |
| Drinking water certification (ACS/WRAS/KTW) | Triple certification ACS + WRAS + KTW — recognised by ERSAR and European regulators | Some products with ACS — verify individually; film validity: 5-10 years | Generally acceptable — no active migration but rough surface and alkaline pH | Certifiable with appropriate gel coat — residual styrene in first months |
| Anti-biofilm surface | Excellent — Ra < 1 µm; 60-80% less biofilm than bare concrete; no biocides | Good while film intact — degrades and creates biofilm substrate as it ages | Poor — rough, porous surface ideal for biofilm and algae | Good with intact gel coat — degrades with UV and impacts |
| Rehabilitation without demolition | Yes — direct installation on existing concrete; 5-15 days service interruption | Yes — but 5-10 year cycle requires recurrent repairs | Yes — but frequent cracking requires periodic retreatments | Partially — only in reservoirs with regular accessible geometry |
| Stored water pH range | pH 4 to 12 — covers acid rainwater, drinking water, industrial process water | Typically pH 5-11 — consult product data sheet | pH 7-14 — alkalinises water in contact; unsuitable for acid water | pH 3-12 with appropriate resin — variable by formulation |
| Accumulated cost over 30 years (relative index) | 100 — single installation, zero specific membrane maintenance | 160 — 3 full reapplications over 30 years | 140 — periodic retreatments and cracking repairs | 150 — gel coat renewal and possible structural replacement |
Performance in the Portuguese Climate
Alentejo and Algarve — Irrigation Reservoirs in Water Stress Zones
With 400-700 mm of annual rainfall concentrated in 5 months, the Alentejo and Algarve have Portugal's largest agricultural irrigation reservoirs — from small 50 m³ tanks for individual vineyards to 5,000-10,000 m³ reservoirs supplying collective irrigation systems. Membriko has extensive experience in rehabilitation and new construction of agricultural reservoirs in these regions, including 30-50 year old concrete structures and stone masonry structures over 100 years old.
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, biofilm and cracking losses are common problems. ERSAR has identified the rehabilitation of these reservoirs as one of the sector's priorities. Membriko installs ACS/WRAS EPDM in municipal reservoirs with coordination of the alternative supply plan — typically 5 to 15 days of interruption for a 500-2,000 m³ reservoir, versus 6 to 18 months for demolition and reconstruction.
Industrial Zones — Process and Fire-Fighting Reservoirs
Industrial parks and high-risk buildings have fire-fighting reservoirs with specific SCIE regulatory requirements. Membriko waterproofs these reservoirs with 2.0 mm EPDM, tested for resistance to extinguishing foam and fire suppression additives. For industrial process reservoirs with cooling water or chemical process water, Membriko specifies the EPDM grade appropriate to the specific chemical composition of the stored water.
North and Centre — Reservoirs with Thermal and Seasonal Variation
In northern and central Portugal, surface reservoirs are subject to water temperature variation of 5 to 30°C between winter and summer. This variation creates contraction and expansion cycles in concrete that degrade rigid coatings. EPDM with 400% elongation accommodates these structural movements without watertightness loss, and maintains water contact certification across the entire service temperature range.
Portugal — Hotel Tourism with Multi-Purpose Water Reservoirs
Four and five-star hotels, resorts and water parks have water reservoirs for multiple purposes: drinking water storage for guest consumption, water reservoirs for pools and spas, irrigation reservoirs for gardens and golf courses, and fire-fighting reservoirs. Membriko has experience in multi-reservoir hotel systems with different certifications — guaranteeing the correct certification level for each reservoir.
Frequently Asked Questions
Yes. ERSAR recognises ACS and WRAS certifications as valid documentation for materials in contact with drinking water in municipal reservoirs. Decree-Law 152/2017 requires that materials do not compromise water quality — Membriko's triple ACS/WRAS/KTW certification is the technical evidence demonstrating this compliance. Membriko delivers the complete technical dossier for ERSAR approval.
Yes — this is one of the most frequent applications for Membriko. Active cracks (with water passage) are injected with potable-water-certified hydro-expansive polyurethane resin before membrane installation. Inactive cracks are filled with epoxy mortar. EPDM with 400% elongation accommodates residual movements of aged concrete without compromising future watertightness. The existing concrete structure is the substrate — demolition or reconstruction is not necessary.
EPDM is suitable for reservoirs from 1 m³ (domestic cistern) to over 10,000 m³ (large-scale municipal or agricultural reservoir). There is no practical upper limit — for very large volumes, Membriko executes field seams on site with the QuickSeam system. The maximum available membrane width is 15.25 m — sufficient to cover the floor of most rectangular reservoirs without underwater seams.
Yes. Fire-fighting reservoirs regulated by SCIE can be waterproofed with EPDM. Membriko specifies 2.0 mm thickness EPDM for these reservoirs, with adhesive and accessories tested for resistance to extinguishing foam and typical fire suppression system additives. WRAS membrane certification is equally valid for the water quality requirements of SCIE reservoirs.
A standard rectangular 500 m³ concrete municipal reservoir typically takes 8 to 12 working days from Membriko, including surface preparation, membrane and accessory installation, watertightness testing and disinfection. Add to this the reservoir draining (1 day) and the refilling and water analysis time (2-3 days) before resuming service. Total service interruption time is 12 to 18 days — versus 6 to 18 months for demolition and reconstruction.
Yes. EPDM is stable in contact with all disinfection systems used in Portugal: chlorination with sodium hypochlorite (up to 2 mg/L continuous residual chlorine, and shock treatments up to 50 mg/L), chloramines, chlorine dioxide, ozone and UV radiation. Chlorine resistance is documented by ASTM D471 tests at 200 ppm and 70°C without any property degradation. For reservoirs using ozone as disinfection agent, EPDM with saturated chain is particularly advantageous: it is intrinsically resistant to ozone due to the absence of C=C double bonds.
Yes. Portugal has many stone masonry reservoirs and tanks over 100 years old, especially on estates in the Alentejo and Algarve. Membriko installs EPDM directly on prepared stone masonry (joints filled, surface levelled with cementitious mortar base, edges rectified). The 400% elongation of EPDM accommodates the irregular movements of stone masonry and discontinuities between stones. This solution has a much lower cost than demolition and concrete reconstruction.
Yes. Membriko issues a 20-year installation warranty for all reservoir waterproofing projects, regardless of volume. For large-scale municipal or agricultural reservoirs, the warranty is complemented by an optional periodic maintenance and inspection contract, including annual inspection with technical report and systematic verification of seams and penetrations. This extended warranty is particularly relevant for managers with regulatory accountability to ERSAR or other supervisory bodies.
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