Polyurethane vs Epoxy: Choosing the Right Coating for Water Tank Relining
- Marc Fitzpatrick
- May 2, 2025
- 3 min read
Updated: Nov 27, 2025
When it comes to relining water tanks, selecting the appropriate coating is crucial for ensuring longevity, safety, and compliance. Two commonly used materials are polyurethane and epoxy coatings. Each has distinct properties that make them suitable for different applications. This article aims to provide facilities managers with a comprehensive comparison to aid in informed decision-making.
Understanding Polyurethane and Epoxy Coatings
Polyurethane Coatings
Polyurethane coatings are known for their flexibility and resistance to UV radiation. They are often used in environments where temperature fluctuations occur, as they can accommodate substrate movement without cracking. Additionally, polyurethane coatings cure relatively quickly, reducing downtime during application.
Epoxy Coatings
Epoxy coatings are renowned for their hardness and strong adhesion to various substrates. They provide excellent chemical resistance, making them suitable for environments where the tank contents may be aggressive or corrosive. However, epoxies are generally more rigid and may not perform as well under conditions involving structural movement.
Key Considerations for Water Tank Relining
Durability and Flexibility
Polyurethane: Offers superior flexibility, making it ideal for tanks that experience temperature-induced expansion and contraction.
Epoxy: Provides a hard, durable surface but may be prone to cracking if the substrate moves.
Chemical and UV Resistance
Polyurethane: Exhibits good resistance to UV radiation, maintaining its integrity and appearance over time.
Epoxy: While chemically resistant, epoxies can degrade under prolonged UV exposure, potentially leading to discoloration and reduced performance.
Application and Curing Time
Polyurethane: Typically cures faster than epoxy, allowing for quicker return to service.
Epoxy: Generally requires a longer curing period, which may extend downtime during maintenance.
Suitability Based on Tank Material and Use
Concrete Tanks
Polyurethane: Its flexibility makes it well-suited for concrete tanks, accommodating any minor movements or settling. Take a look at this case study which shows our engineering team relining a large concrete water tank with polyurethane - Concrete Water Tank Reline Bath - Case Study | Titan Water
Epoxy: Can be used on concrete but may require additional surface preparation to ensure proper adhesion.
Steel Tanks
Polyurethane: Provides a protective barrier against corrosion, especially in outdoor settings where UV exposure is a concern. This is a case study of a steel tank relined by our team recently - Steel Water Tank Reline Edinburgh | Leak Repair Case Study | Titan Water
Epoxy: Offers excellent adhesion to steel surfaces and strong chemical resistance, beneficial for tanks storing aggressive substances.
Potable Water Storage
Both polyurethane and epoxy coatings can be formulated to meet safety standards for potable water tanks. It's essential to verify that the chosen product complies with relevant regulations and certifications. For instance, in the UK, the chose produce should be WRAS or KIWA approved.
Maintenance and Longevity
Polyurethane: Its flexibility can lead to a longer service life in environments with structural movement or thermal cycling.
Epoxy: Offers a hard, durable finish that resists abrasion but may require more frequent inspections in dynamic environments.
Conclusion
Selecting between polyurethane and epoxy coatings for water tank relining depends on various factors, including tank material, environmental conditions, and the nature of the stored contents. Polyurethane's flexibility and UV resistance make it suitable for outdoor and concrete tanks, while epoxy's hardness and chemical resistance are advantageous for steel tanks and aggressive substances.
For a more detailed understanding of water tank relining options and to explore our range of services, please visit our How to Reline a Water Tank page, or check out some of our Tank Relining Case Studies.
