Among the various concrete pool crack repair methods available, the Polyurethane Foam Crack Injection method stands out as a highly effective solution, offering several advantages over common concrete repair epoxies. In this article, we will discuss

  • how polyurethane foam crack injection works,
  • the advantages of using polyurethane foam for concrete pool crack repair and compare it with concrete crack repair epoxies.

How Does Polyurethane Foam Crack Injection Work?

Polyurethane foam injection, also known as polyurethane foam crack injection, is a method used to repair cracks and leaks in concrete structures, including concrete swimming pools, gunite pools, shotcrete pools, spas, and fountains. The process involves injecting a specialized polyurethane foam into the cracks, where it expands and cures to form a durable and watertight seal. Here’s a step-by-step overview of how polyurethane foam injection works:

Preparation: The first step in the process is to prepare the surface of the concrete, ensuring it is clean and free of debris. This may involve using a wire brush or pressure washing to remove any loose particles or contaminants that could interfere with the adhesion of the foam.

Identification of Cracks: Next, the cracks in the concrete are identified and assessed to determine their size, shape, and extent. This evaluation helps determine the appropriate injection technique and the amount of foam needed to fill the cracks effectively.

Injection Ports Installation: Small injection ports are installed along the length of the cracks at 12” intervals using a 2-part epoxy. These ports serve as entry points for the polyurethane foam and allow for precise injection into the crack.

Injection of Polyurethane Foam: The specialized polyurethane foam is then injected into the cracks through the installed injection ports using a standard caulking gun.

Expansion and Curing: The polyurethane foam reacts and begins to expand when it makes contact with moisture, filling the cracks and surrounding spaces. As it expands, the foam adheres to the concrete surfaces and cures within a relatively short period, typically within minutes, depending on the specific formulation and environmental conditions.

Sealing and Waterproofing: As the polyurethane foam expands and cures, it forms a strong, flexible, and waterproof seal within the cracks. This seal effectively prevents further water infiltration.

Port Removal and Surface Cleanup: Once the foam has fully cured, the injection ports are removed, and any excess foam protruding from the surface is trimmed or scraped away. The repaired area is then cleaned and inspected to ensure a smooth and uniform finish.

Fig. 1 How polyurethane foam crack injection works using AquaBond PFK-377 and DMK-377

Advantages of Using Polyurethane Foam Crack Injection

Polyurethane foam crack injection offers several advantages over traditional concrete repair methods for repairing leaks in concrete, shotcrete, or gunite swimming pools and other structures.


  • Seamless Penetration and Expansion: Polyurethane foam is a versatile material known for its ability to penetrate even the tiniest of cracks in concrete. When injected into these cracks, the foam expands, effectively sealing off the leak pathway. This seamless penetration ensures comprehensive coverage and a long-lasting repair.
  • Flexibility and Durability: Unlike rigid epoxy compounds, polyurethane foam remains flexible after curing. This flexibility allows it to withstand the natural movement of concrete without cracking or breaking, ensuring durability over time. As swimming pools are subject to temperature fluctuations and ground movement, this flexibility is crucial for maintaining the integrity of the repair.
  • Water Resistance: Polyurethane foam exhibits excellent water resistance properties, making it an ideal choice for repairing leaking swimming pools. Once injected and cured, the foam forms a watertight seal that effectively prevents further water infiltration, eliminating the source of leakage.
  • Quick and Non-Disruptive Application: Polyurethane foam injection is a relatively quick and non-disruptive process compared to traditional concrete repair methods. Contractors can efficiently inject the foam directly into the cracks without the need for extensive excavation or disruptive construction work. This minimally invasive approach reduces downtime and inconvenience for pool owners.

AquaBond PF-37 Polyurethane Crack Injection Foam

Aquabond PF-37 Polyurethane Crack Injection Foam is a hydrophobic, single-component, VOC-compliant polyurethane injection resin designed to repair leaking joints and cracks in concrete. The cured hydrophobic material exhibits the elasticity and durability to stop leaks permanently. After reacting to minimal amounts of water, the resulting foam will maintain its physical form and not be subject to shrinkage.

Aquabond PF-37 expands up to 25 times its initial volume, curing into a tough, adhesive foam capable of withstanding thermal cycles and crack movement.


    • 100% solids.
    • Expands up to 25 times the initial volume
    • Dispenses as a single component
    • Controllable reaction times
    • Outstanding adhesion
    • Non-hazardous shipping
    • Non-flammable
    • Cures inert, non-toxic, permanent seal


Physical Properties – Liquid
Aquabond PF-37 Test Method
Viscosity 300 cps ASTM D-1638
Specific Gravity 1.10 ASTM D-1475
Color Light amber when liquid – cures to white color  
Flash Point > 250 ºF ASTM D-92


Solid Cured
Density 5 lbs/ft³ ASTM D-1622
Elongation 140% ASTM D-638
Tensile Strength 25 psi ASTM D-638
Toxicity Non-toxic  



The recommended working temperature is between 55° and 85°.

Between 55° and 85°, the mixed Surface Seal will begin setting up within 4-7 minutes. The Surface Seal should be ready for injection after about 20-30 minutes.

Between 40° and 55°, the Surface Seal working time is 8-12 minutes. You should allow at least 30 to 60 minutes of cure time before beginning the injection procedure.

Do not perform this repair below 40° F.



AquaBond offers a PFK-377 polyurethane foam crack injection kit that includes 2-Part Surface Seal paste, Expanding Polyurethane Foam, Injection Ports, Port Plugs, Water Bottle and Flush Hose, Rubber Fittings, Mixing Sticks, Putty Knife, Gloves and Detailed Instructions.

The DMK-377 polyurethane foam crack injection kit also includes the AquaBond DM-250 High Thrust Caulking Gun.

The Difference Between Epoxy and Polyurethane Foam for Concrete Repair


When considering the best approach for repairing concrete, particularly in the context of swimming pools, the choice often boils down to epoxy and polyurethane foam. Each option presents distinct advantages and applications, catering to different needs and scenarios.

Concrete repair epoxies excel in two key areas for pool repairs: exceptional structural bonding and superior chemical resistance.

  • Exceptional Structural Bonding: Concrete repair epoxies are renowned for their exceptional bonding strength, providing structural reinforcement to damaged concrete surfaces. This characteristic makes them suitable for restoring the overall integrity of the pool structure.
  • Chemical Resistance: Epoxies offer superior resistance to chemicals, making them well-suited for pool environments where exposure to chlorine and other pool chemicals is inevitable. This resistance ensures that the repair remains intact even in harsh chemical conditions.

While both methods have their merits, polyurethane foam crack injection emerges as an excellent method for repairing leaking concrete swimming pools in many scenarios. Its seamless penetration, flexibility, water resistance, and non-disruptive application make it particularly well-suited for addressing common pool leakage issues. However, for more extensive structural repairs and situations requiring precise application or chemical resistance, concrete repair epoxies are a suitable option.

Consulting a qualified pool professional is crucial for selecting the most suitable repair method. They can assess the specific damage and recommend the optimal solution based on your pool’s unique needs.

Looking for a polyurethane crack injection foam to repair concrete cracks? Try professional-grade AquaBond® PFK-377 or DMK-377 polyurethane foam injection kit today!



What Is Polyurethane Crack Injection Foam?

Polyurethane crack injection foam is a specialized type of foam used to repair cracks and leaks in concrete structures like swimming pools. It’s flexible, expands to fill cracks completely, adheres well to concrete, and resists water and chemicals. It cures rapidly, minimizing downtime, and its application is less disruptive compared to traditional repair methods.

How Long Does Polyurethane Foam Injection Last?

The longevity of polyurethane foam injection repairs can vary depending on factors such as the quality of the materials used, the expertise of the application, the severity of the cracks, and the environmental conditions. However, when properly applied, polyurethane foam injection repairs are generally durable and long-lasting.

In ideal conditions, polyurethane foam injections can last for decades without needing further attention. The flexible nature of the foam allows it to accommodate minor shifts in the concrete structure without cracking or breaking, which helps maintain the integrity of the repair over time.

Regular maintenance and inspections can also help prolong the lifespan of polyurethane foam injections. Periodic checks for new cracks or signs of deterioration can allow for timely repairs, preventing minor issues from escalating into larger problems.

How Do You Inject PU Foam?

To inject PU foam, the typical injection process includes these steps:

  1. Clean the crack and install injection ports.
  2. Use an injection gun to fill the crack with foam, starting from the bottom.
  3. Let the foam expand and cure.
  4. Remove excess foam and cleanup.
  5. Inspect for proper sealing.

In practice, you should always follow the manufacturer’s instructions.

Ready to repair your concrete swimming pool? Try AquaBond PF-37 Polyurethane crack injection foam for a durable, flexible, and watertight seal. Get started with our PFK-377 or DMK-377 polyurethane foam crack injection kits, equipped with everything you need for a successful repair. Don’t let leaks ruin your pool experience. Choose AquaBond Adhesives for professional-grade solutions and enjoy the benefits of the polyurethane foam injection method. Contact us today!