Protecting Municipal Water Tanks with Surface Coating

While water is essential to life, it’s one of the most destructive elements on the planet. Without the use of a water tank surface coating, the substrate in a municipal tank is vulnerable to factors such as corrosion, deterioration, and nitrification. The destructive problems compromise the safety of the water within a tank and reduce the tank’s service life. Maintenance that includes the proper application of surface coatings mitigates these risks and increases a tank’s durability.

Water Tank Designs and Associated Risks

By design, municipal water tanks should never affect the safety of the water, as it’s already susceptible to environmental influences like mineral accumulation, pH changes, bacteria, and algae. Common tank types include:

• Fiberglass: Fiberglass water tanks are vulnerable to sunlight.
• Steel: Steel tanks are susceptible to corrosion.
• Concrete: Concrete deteriorates with time. Wet/dry cycles make the material susceptible to sulfate attacks and salts. Freeze/thaw cycles may cause the formation of cracks. Even high-quality concrete is at risk.

Water Tank Surface Coatings for Added Protection

Surface coatings protect the inside of municipal water tanks from deterioration and corrosion, as it forms a physical barrier between the water and the walls of the tank. Some protective epoxy coatings also give tanks an added layer of chemical resistance. The best type of coating to use depends on the design of the tank, the material from which it is made and the standards outlined by the American Water Works Association.

Fiberglass and polyethylene tanks, particularly those stored above ground, may require surface coatings on the exterior walls to protect them from the impact of UV rays. Without the protective coating, the tank’s exterior will degrade. It’s not uncommon for water tanks made of other materials to have an exterior surface coating that protects against the elements and prevents heat absorption.

The best time to apply surface coatings to a water tank is before its installation to protect it from:

• Spalls
• Leaks
• Abrasives (e.g., silt, sand, and other debris in water)
• Sunlight
• Freezing weather
• Cracks
• Tensile stresses
• Scale
• Organic and inorganic deposits (e.g., calcium, biofilm, manganese, and iron)
• Chemical attacks (e.g., low pH levels of acid in the water)
• Chlorine losses in the stored water

If a contractor didn’t apply a water tank surface coating before a tank’s installation, it is possible to apply it during maintenance.

The Importance of Surface Preparation Before Applying a Water Tank Surface Coating

Protective coatings extend the life of water tanks and help protect the water they hold. The success of the coatings depends on the tank’s surface preparation. It is not enough to merely power-wash or use washouts to prepare the surface because they don’t fully remove organic and inorganic deposits. Leftover deposits reduce the coating’s durability and cause it to bubble, crater, or crack.

When applying surface coatings, it’s also crucial to create the ideal environment for it to dry. Depending on the time of year and the tank’s location, the temperatures and relative humidity levels may prolong a protective coat’s drying time. Temporary climate control solutions lower humidity levels and promote optimal surface temperatures for the water tank surface coating to adhere to the substrate.

Polygon specializes in temporary climate control solutions that improve the performance of protective coatings during the preparation, application, and curing stages. The solutions will help you stay on top of deadlines, reduce maintenance costs and prolong the amount of time between coating applications. Contact Polygon today to learn more about implementing its solutions with your municipal water tank maintenance projects.

[Photo by U.S. Department of Agriculture via CC License 2.0]