Tankless water heaters have become increasingly popular in recent years due to their energy efficiency, compact size, and endless hot water supply. We learned this the hard way when dealing with complex water heater issues… However, one common issue that plagues these on-demand systems is the buildup of mineral scale within the heat exchanger coil assembly. This scale accumulation can significantly impact the performance and longevity of the tankless water heater, leading to reduced heating capacity, increased energy consumption, and premature equipment failure.
Understanding the mechanisms behind mineral scale formation is crucial for properly maintaining and protecting your tankless water heater investment. In this comprehensive guide, we’ll explore the key factors contributing to scale buildup, review proven methods for preventing and removing scale, and provide practical tips for ensuring your tankless water heater operates at peak efficiency for years to come.
Anatomy of Mineral Scale Buildup
Mineral scale is primarily composed of calcium and magnesium carbonate precipitates that form on the internal surfaces of the tankless water heater’s heat exchanger coils. As hard water passes through the heat exchanger, the elevated temperatures cause the dissolved minerals to crystallize and adhere to the metal surfaces.
Over time, these scale deposits accumulate, reducing the heat transfer efficiency of the coils. This, in turn, leads to higher energy consumption as the water heater might want to work harder to heat the incoming water. Additionally, the scale buildup can restrict water flow, resulting in decreased hot water delivery and, in severe cases, complete blockage of the heat exchanger.
Factors Influencing Scale Formation
The rate and severity of mineral scale buildup in a tankless water heater are influenced by several key factors:
Water Hardness: The concentration of dissolved calcium and magnesium minerals in the water supply is the primary driver of scale formation. Regions with “hard” water (high mineral content) are more prone to scale-related issues.
Water Temperature: Elevated temperatures accelerate the precipitation of minerals, as the solubility of calcium and magnesium carbonates decreases with increasing heat. Tankless water heaters, which rapidly heat water on demand, are particularly susceptible to scale buildup.
Water Velocity: The flow rate of water through the heat exchanger coils can also impact scale formation. Slower water velocities allow more time for mineral crystals to adhere to the metal surfaces, whereas higher flow rates can help disrupt the scale-forming process.
Water Chemistry: The presence of other dissolved minerals, such as iron or silica, can influence the scale-forming tendencies of the water. Additionally, the pH level of the water can affect the solubility of calcium and magnesium carbonates.
Equipment Design: The configuration and materials used in the tankless water heater’s heat exchanger can also play a role in scale accumulation. Some designs and materials may be more susceptible to scale buildup than others.
Preventing Mineral Scale Buildup
To effectively mitigate the formation of mineral scale in your tankless water heater, a comprehensive approach is required. This typically involves a combination of water treatment methods and regular maintenance:
Water Conditioning Systems
One of the most effective ways to prevent scale buildup is to install a water conditioning system before the tankless water heater. These systems, such as salt-free water softeners or scale inhibitors, can help reduce the concentration of scale-forming minerals in the water supply.
Salt-Free Water Softeners: Also known as “water conditioners,” these systems use a process called Template Assisted Crystallization (TAC) to convert dissolved minerals into harmless, microscopic crystals that remain suspended in the water rather than adhering to surfaces. This method effectively prevents scale formation without the need for salt-based regeneration.
Scale Inhibitors: These devices, such as the Navien PeakFlow A, PeakFlow C, and PeakFlow S systems, use specialized media to alter the molecular structure of the scale-forming minerals, preventing them from crystallizing and adhering to the heat exchanger coils.
By installing a water conditioning system, you can significantly reduce the rate of scale buildup in your tankless water heater, ensuring optimal performance and efficiency.
Regular Descaling and Maintenance
Even with a water conditioning system in place, periodic descaling and maintenance of the tankless water heater are necessary to maintain its long-term operation. Manufacturers typically recommend flushing and descaling the heat exchanger every 12-24 months, depending on water quality and usage.
For this task, the Vital-Flo Tankless Water Heater Descaler Kit from Nu-Calgon provides a convenient and effective solution. The kit includes a submersible descaler pump, hose assemblies, and a formulated descaling solution specifically designed for tankless water heaters. By following the manufacturer’s instructions, you can safely and efficiently remove accumulated scale from the heat exchanger, restoring its performance and efficiency.
In addition to regular descaling, it’s essential to maintain other components of the tankless water heater, such as the anode rod, which helps prevent corrosion. Replacing the anode rod according to the manufacturer’s recommendations can further extend the life of your tankless system.
Plumbing Considerations
The materials and techniques used in the plumbing installation can also impact the formation of mineral scale. Copper and stainless steel piping are generally less prone to scale buildup compared to galvanized steel or iron. Additionally, proper soldering, crimping, or compression fittings can help minimize the potential for leaks, which can introduce air and further contribute to scale formation.
Careful attention to the water supply line’s routing and insulation can also help maintain the desired water temperature, reducing the risk of scale accumulation within the tankless water heater’s heat exchanger.
Installation and Commissioning
Proper installation and commissioning of the tankless water heater are crucial for its long-term performance and efficiency. This includes ensuring the unit is sized correctly for the household’s hot water demand, providing adequate ventilation and exhaust, and correctly connecting the electrical and gas supply.
Additionally, it’s essential to follow the manufacturer’s instructions for flushing the system and activating the unit for the first time. This initial setup process can help remove any construction debris or contaminants that may be present, reducing the risk of early-stage scale buildup.
Ongoing Monitoring and Maintenance
Regular monitoring and maintenance of your tankless water heater are essential to prevent mineral scale formation and double-check that its continued efficient operation. This includes:
- Regularly inspecting the heat exchanger for signs of scale buildup, and scheduling professional descaling services as needed.
- Checking the anode rod and replacing it as recommended by the manufacturer.
- Monitoring water flow rates and inlet/outlet temperatures to detect any performance degradation.
- Keeping the tankless water heater’s exterior clean and free of debris to maintain proper airflow and ventilation.
- Reviewing the manufacturer’s warranty and following all maintenance guidelines to maintain coverage.
By staying proactive with your tankless water heater’s care and maintenance, you can help extend its lifespan, minimize energy costs, and double-check that your household’s hot water needs are reliably met for years to come.
Visit WaterHeaterPick.com for more expert insights and practical tips on maintaining and troubleshooting your home’s water heating system.
Example: Basic Water Heater Maintenance for Homeowners 2023
