▽ +09.00Waterproofing · Water-retaining structures
Water tank waterproofing
A tank needs waterproofing that keeps water in and ground water out, and an internal lining suitable for drinking water, according to the product.
Engineering view
What is water tank waterproofing?
An underground tank works both ways: the water inside pushes out and ground water may push in. Any untreated crack or joint means losing water, or contaminating drinking water with what comes in from the soil.
So the tank is treated inside with a system suitable for drinking water according to the product’s certification, and outside where it can be reached before backfilling — with particular care at the wall–floor junction and at pipe entries.
52%
of portfolio projects include tanks
Prequalification 2026 — prevalence of systems across portfolio projects (percentages overlap)
Problems it solves
What goes wrong
Water loss
The level drops with no visible leak: cracks, joints or pipe entries.
Contamination risk
Ground water and salts enter an underground tank through cracks.
Lining failure
A lining applied over a damp or unprepared surface blisters and peels.
Diagnose by symptom
From the system’s documented advantages
Key benefits
A smooth, hygienic, easy-to-clean surface
Chemical and abrasion resistance
A strong bond to prepared concrete
Documented advantages of Epoxy tank linings — every system also has limits, listed on its page.
Applications
Where it applies
- W.01
Potable water tanks
An internal lining approved for contact with drinking water, per the product.
- W.02
Underground tanks
Internal and external waterproofing; cracks and joints injected where needed.
- W.03
Roof tanks
Concrete tanks on the roof under heat: internal lining and external protection.
The water side
Inside or outside
Inside face
Inside (the stored-water side): the internal lining keeps the water in and touches it directly, so it must be suitable for drinking water according to the product certificate.
Outside face
Outside (the soil side): keeps ground water and salts away from the concrete and goes on before backfilling. In existing tanks the internal system and crack repair carry the load.
Building condition
New or existing
New building
New tank: pour joints treated during construction, an external system before backfill, then the internal lining and a fill test before commissioning.
Existing building
Existing tank: drain, clean and inspect, repair the concrete and inject cracks, then a new internal lining and a fill test.
By technology
Available systems
- Sheet membranesGeomembrane & HDPE linersPolymer sheets thermally welded on site to line lakes, large reservoirs and flood channels.
- Liquid-applied & liningsPolyurea waterproofing (hot & cold)A fast-curing, tough polyurea layer, hot-sprayed with dedicated equipment or cold-applied.
- Liquid-applied & liningsEpoxy tank liningsA continuous, smooth epoxy lining for water tanks, using products certified for drinking-water contact.
- Cementitious & crystallineCementitious waterproofingPolymer-modified cementitious coats that bond to concrete, for basements, tanks, pools and wet areas.
- Cementitious & crystallineCrystalline waterproofingChemicals that react with moisture in concrete and grow crystals that block its pores and hairline cracks.
- InjectionCrack injection (epoxy & PU)Resin injected into cracks: epoxy to re-bond, or polyurethane to stop water.
- Concrete repair & protectionConcrete repair with repair mortarsBreaking out damaged concrete, treating the reinforcement and rebuilding the section with a suitable repair mortar.
How the system is chosen
| Situation | Suitable systems | Why |
|---|---|---|
| An internal lining for a drinking-water tank | Tank epoxy Cementitious Polyurea | Subject to the product’s potable-water certification. |
| The tank concrete itself | Crystalline | Blocks the pores within the concrete mass. |
| Leaking cracks or joints | Crack injection Concrete repair | Before any new lining. |
| Large open reservoirs and ponds | Geomembrane liners | A welded geomembrane liner. |
A starting point only: the final system follows the inspection, the approved specification and the product TDS.
Layers
System build-up
System build-up5 layers
Epoxy tank linings
Select a layer to see what it does.
Finish coatCore layer
A second epoxy coat that completes the specified thickness and gives a smooth surface.
First coatCore layer
A continuous epoxy coat over walls, floor and soffit, as specified.
Primer
Bonds the lining to the prepared concrete.
Repair and levelling mortar
Fills honeycombing and voids before lining.
Where needed
Tank concrete
Mechanically prepared, and as dry as the product requires.
A typical build-up for this application, top to bottom.
System page: how it works and its limitsBrand-neutral
Manufacturers & approvals
- Weber (Saint-Gobain)Approved applicatorCertificate
- Fosroc (Saint-Gobain)Approved applicatorCertificate
- AwazelApproved applicatorCertificate
- AIM IndustriesApproved applicator · Sister companyCertificate
- IzomaksApproved applicatorCertificate
- DCP SaudiCertified applicatorCertificate
- PenetronCertified applicatorCertificate
We start from the engineering of the system, then the product. Manufacturers appear here only with their documented relationship; this does not imply a commercial partnership.
Before work starts
Surface preparation
- Tank drained, cleaned and dried where the system needs it.
- Honeycombing and tie holes repaired; cracks injected.
- Mechanical preparation to remove laitance.
- Good ventilation while working inside the tank.
Sequence
Installation process
Inspect
Cracks, joints, pipe entries and concrete condition.
Repair
Repair mortar and crack injection.
Details
Wall–floor junction, corners and pipes.
Internal lining
In the coats and thickness the TDS sets.
Cure and fill test
Tank filled and the level watched for the specified time.
Clean and hand over
As potable-water tank commissioning requires.
Inspection & testing
QA/QC
- Surface preparation inspected before lining.
- Dry-film thickness (DFT) or coverage measured.
- Adhesion tested where specified.
- A recorded fill test before commissioning.
- The product’s potable-water certificate in the submittal.
What we avoid
Common failures
A product not approved for drinking water
Choose the lining by its certificate, not by its colour.
Lining over live cracks
The crack reopens and splits the lining.
Wall–floor junction neglected
The point where most tanks leak.
Filled before full cure
Affects adhesion and water quality.
Executed references
From our projects
Hotel & resortInterContinental Abha
Abha, Asir Region
Al-Safa Hills
Al-Safa, Riyadh
Residential compoundMakeen 68
Al-Rayyan, Riyadh
HeadquartersAl Rajhi Headquarters
Al-Ghadeer, Riyadh
Masheed projects
Riyadh Region
Wahla projects
Al-Narjis and Dirab, Riyadh Region
Go deeper
Technical references
Before you ask
Questions
Are your tank systems safe for drinking water?
Inside drinking-water tanks we use systems suited to that use according to the product’s certificate, and we submit the product data and certificate for approval before work starts.
How is a tank tested after waterproofing?
With a fill test: once the lining has cured, the tank is filled and the water level is watched for the period the specification sets; the result is recorded before commissioning.
What is the best waterproofing for an underground water tank?
Inside, a lining approved for drinking-water contact (epoxy, cementitious or another approved system), after the cracks, construction joints and pipe entries are treated. Outside, on new tanks, waterproofing that protects the concrete from groundwater. The tank is fill-tested before it goes into service.
Is a roof tank waterproofed differently from an underground tank?
Yes. A roof tank faces sun and heat, so its outer face needs UV-resistant protection, while an underground tank faces soil and groundwater outside. Inside, both need a lining approved for drinking water.
Will the lining leave a taste or smell in the water?
A product approved for drinking water is applied and left to cure fully as its data sheet requires, then the tank is washed and disinfected before use; following these steps is what prevents taste and odour.
Next step
A leaking tank, or one that needs a potable-water lining?
Send the tank size and type — ground or roof — for a detailed offer, or ask for a technical review.