Waterproofing work of concrete tank in progress

Waterproofing Underground and Overhead Concrete Tanks: A Comprehensive Guide

Concrete tanks are essential components of various infrastructure projects, such as water storage systems, sewage treatment plants, and industrial facilities. These tanks serve as critical storage units for liquids, and their longevity and functionality heavily rely on effective waterproofing. Whether these tanks are underground or overhead, ensuring their waterproofing is vital to prevent leaks, structural damage, and contamination. In this guide, we’ll delve into the importance of waterproofing, methods, and best practices for waterproofing both underground and overhead concrete tanks.

Importance of Waterproofing

Waterproofing is the process of making a structure resistant to the penetration of water, preventing it from causing damage or compromising the integrity of the construction. In the context of concrete tanks, effective waterproofing is crucial for several reasons:

Preventing Water Leakage

 The primary purpose of a concrete tank is to store liquids securely. Without proper waterproofing, water can seep into or out of the tank, leading to water loss or contamination.

Structural Integrity

Water infiltration can weaken the concrete structure over time, potentially leading to cracks and deterioration. This compromises the tank’s structural integrity and longevity.

Corrosion Protection

In tanks storing corrosive liquids, waterproofing prevents these substances from coming into contact with the steel reinforcement within the concrete. This reduces the risk of corrosion and extends the tank’s service life.

Methods for Waterproofing Underground Concrete Tanks 

Membrane Waterproofing

This method involves applying a waterproofing membrane on the exterior surface of the concrete tank. Popular options include bituminous membranes, polyurethane membranes, and cementitious coatings. The membrane creates a barrier against water infiltration.

Integral Waterproofing

Integral waterproofing involves adding water-repellent admixtures directly into the concrete mix during construction. These admixtures chemically bond with the concrete, making it impermeable to water.

Crystalline Waterproofing

Crystalline waterproofing products can be applied as a coating or mixed into the concrete. These products penetrate the concrete and form crystals, which block water pathways and enhance durability.

Cementitious Waterproofing

Cementitious waterproofing compounds are a blend of cement, sand, and polymer additives. They are applied as slurry to the tank’s surface and bond with the concrete, creating a waterproof layer.

Best Practices for Waterproofing Underground Concrete Tanks 

Surface Preparation

Ensure that the tank’s surface is clean, dry, and free of any loose debris or contaminants before applying the waterproofing material.

Proper Application

Follow the manufacturer’s instructions for the chosen waterproofing method carefully. Apply multiple coats if necessary, allowing for adequate drying time between coats.

Crack Repair

Repair any existing cracks in the concrete before waterproofing. Cracks can compromise the effectiveness of the waterproofing system.

Quality Materials

Invest in high-quality waterproofing materials and membranes. Cutting corners on materials can lead to early failure.

Methods for Waterproofing Overhead Concrete Tanks

Overhead concrete tanks, often used for water storage in buildings, have specific waterproofing requirements:

Liquid Applied Membrane

Liquid-applied membranes, such as polyurethane or epoxy coatings, are commonly used for overhead tanks. They provide a seamless, flexible barrier against water intrusion.

Sheet Membrane

Self-adhesive sheet membranes can be applied to the tank’s surface, providing an effective waterproofing layer. These are particularly useful for irregularly shaped tanks.


Install water stops at the joints and penetrations of the overhead tank to prevent water from seeping through these vulnerable areas.

Best Practices for Waterproofing Overhead Concrete Tanks 

Proper Surface Preparation

Ensure the tank’s surface is clean, smooth, and free from any defects or protrusions before applying the waterproofing membrane.

Adequate Slope

Design the tank with a slight slope to encourage water drainage and prevent the accumulation of standing water on the surface.

Reinforcement Protection

Use a protective coating or wrap for steel reinforcement bars to prevent corrosion caused by moisture and chemicals.

Regular Inspection

Periodically inspect the overhead tank for any signs of damage, such as cracks or delamination, and repair them promptly to maintain the waterproofing integrity.


Waterproofing is an essential aspect of constructing and maintaining both underground and overhead concrete tanks. Proper waterproofing ensures the longevity, functionality, and safety of these vital storage units. Whether using membrane systems, crystalline waterproofing, or integral waterproofing, following best practices and using high-quality materials are crucial for success. By taking these precautions, you can safeguard your concrete tanks against water infiltration, prolong their lifespan, and ensure they continue to perform their intended functions effectively.

In this instalment of our comprehensive guide, we delved deeply into the intricacies of waterproofing both underground and overhead tanks. We offered an in-depth exploration of the methodologies involved in ensuring these tanks remain watertight.

To further streamline and demystify the complex task of waterproofing overhead and underground tanks, we’ll be dedicating next week’s segment to demonstrating how Sturdflex can be an invaluable ally in achieving a waterproof seal for these concrete tanks. Stay tuned for a detailed examination of how Sturdflex can simplify the waterproofing process.