How to Descale a Tankless Water Heater Like a Pro: Instructions, Video, Tips

Tankless water heaters are a modern, energy-efficient way to supply hot water, but they require regular maintenance to perform at their best. Over time, mineral deposits accumulate inside the unit, affecting its proper function and shortening the lifespan of your heater. Learning how to descale a tankless water heater is key to keeping it in optimal condition.

Descaling your tankless water heater removes these deposits, restoring optimal performance and preventing costly repairs. Whether you’re tackling this task yourself or hiring a professional, understanding the process is essential for keeping your system running smoothly.

This guide will walk you through everything you need to know, from why, to tips and instructions on how to do it effectively and safely.

Why Descaling is Important and How to Spot the Signs of a Problem

Descaling a tankless water heater is essential for maintaining its efficiency and extending its lifespan. Over time, minerals like calcium and magnesium from hard water build up inside the heat exchanger, creating scale. This buildup can damage and clog the walls inside your heat exchanger, restricting water flow, reducing heating efficiency, and forcing the system to work harder, increasing energy consumption. If left unaddressed, excessive scaling can lead to costly repairs or premature failure of the unit. Regular descaling ensures optimal performance and helps you avoid these issues.

Signs your tankless water heater needs descaling include reduced water pressure, fluctuating water temperatures, and visible error codes indicating scale buildup. If you notice it takes longer for hot water to flow or that your energy bills are rising, it’s a clear signal that mineral deposits may be compromising your system. Catching these signs early allows you to descale before major problems develop.

Pros & Cons of Descaling a Tankless Water Heater

As mentioned before, regular descaling keeps your tankless water heater running efficiently and can extend the life of your unit, saving you from expensive repairs or replacements. It also helps maintain consistent water temperatures and lowers energy bills, as your water heater doesn’t need to work as hard.

Additionally, the process improves water quality by reducing the chance of sediment entering your water supply.

On the downside, descaling requires time, effort, and a basic understanding of the process. For homeowners unfamiliar with the procedure, mistakes such as using the wrong cleaning solution or improperly flushing the system can cause damage.

The cost of purchasing the necessary equipment, like a submersible pump and hoses, can add up, especially for one-time users. If descaling is not done correctly, residual solution may remain in the system, potentially affecting water quality or system performance.

DIY vs. Professional Descaling

Pros:

• Cost-Effective: DIY saves money on professional fees, while professionals offer value through expertise and comprehensive inspections.
• Convenience: DIY allows you to work on your schedule, while professionals save you time by handling the task efficiently.
• Learning Opportunity: DIY helps you understand your water heater better, while professionals can spot and fix other issues during the process.

Cons:

• Risk of Mistakes: DIY carries the risk of incorrect procedures that can damage the unit, while professional service eliminates this but comes at a higher cost.
• Time Commitment: DIY can be time-consuming for beginners, while scheduling a professional may not always align with your availability.
• Expertise Gap: DIY may miss subtle system issues, while relying on professionals can lead to dependency and a lack of maintenance knowledge.

Tools and Products for Effective Descaling

Descaling a tankless water heater requires specific tools and products to ensure the process is thorough and safe. Here’s what you’ll need:

• Submersible Pump. A submersible pump is essential for circulating the descaling solution through your water heater. This tool ensures that the cleaning solution flows continuously, effectively breaking down and flushing out mineral deposits.
• Flexible Hoses. Two flexible hoses connect your water heater’s service ports to the pump and a bucket. These hoses allow the solution to flow in and out of the system smoothly. Ensure the hoses are compatible with your water heater’s service valves.
• Descaling Solution or White Vinegar. For commercial solutions, choose a product specifically designed for tankless water heaters. These solutions are formulated to dissolve mineral deposits without harming the system. Alternatively, white vinegar is an affordable, eco-friendly option, though it may require longer circulation times to achieve the same results.
• Two 5-Gallon Buckets. One bucket holds the descaling solution, while the other collects the wastewater after it’s circulated through the system. Using two buckets helps you separate the clean and dirty solution for easier disposal.
• Adjustable Wrenches or Pliers. These tools are used to connect and disconnect the service hoses securely to the water heater’s isolation valves.
• Clean Water Supply. Fresh water is necessary for flushing out the solution after the cleaning process. This ensures no residue remains in the system.

How to Descale a Tankless Water Heater: Instructions

Descaling is a straightforward process if done correctly. Follow these detailed steps (this is how Noritz does) to ensure effective maintenance and avoid damage to your system:

Preparation

• Turn Off the Power:
  For electric water heaters, switch off the power at the circuit breaker. For gas water heaters, turn off the gas supply to ensure safety.
• Shut Off the Water Supply:
  Close the cold water valve and the hot water valve to isolate the unit from the main water supply (see below).

Disconnect the Water Heater

• Locate and Close the Isolation Valves:
  Most tankless water heaters have isolation valves. Close these valves to prevent water from entering or leaving the unit during the descaling process. If there are no isolation valves, you’ll need to shut off the main water supply to the entire house before beginning the process. To disconnect the unit, you’ll typically need to remove the hoses from the water inlet and outlet or directly from the service ports. This will isolate the tankless water heater from the rest of the plumbing, allowing you to safely perform the descaling.
• Attach Flexible Hoses to the Service Ports:
  Connect one hose to the cold water service port and the other end to the pump. Attach another hose to the hot water service port, with its other end placed in an empty bucket. Secure all connections with adjustable wrenches to prevent leaks.

Prepare the Descaling Solution

• Mix the Solution:
  Fill one 5-gallon bucket with water, then add the recommended amount of descaling solution or white vinegar. If using vinegar, you’ll typically need to use an equal amount of vinegar to water for a more effective clean. The other bucket is for the waste water.
• Set Up the Pump:
  Place the submersible pump, connected to the cold water side, into the bucket containing the solution. The pump will then circulate the solution through the heater.

Running the Descaling Solution

• Start the Pump:
  Turn on the submersible pump, allowing the descaling solution to flow through the water heater. This process will usually take about 30-60 minutes, depending on the level of scale buildup. The solution should recirculate through the unit continuously.
• Monitor the Process:
  Keep an eye on the pump and hoses to ensure everything is running smoothly. If you notice any issues, such as a leak or pump failure, turn off the system and address the problem before proceeding.

Rinse the System

• Drain the Descaling Solution:
  After the recommended time, turn off the pump and disconnect the hoses. Carefully drain the used solution into a container for disposal.
• Flush with Clean Water:
  Attach the hoses to the clean water supply and run fresh water through the system for 10-15 minutes to flush out any remaining descaling solution. This ensures there’s no residue left in the unit.

Reconnect and Test

• Reattach the Hoses:
  Once flushing is complete, remove the service hoses and reconnect the cold and hot water supply lines.
• Open the Isolation Valves:
  Open the cold and hot water valves to restore water flow to the heater.
• Turn the Power or Gas Back On:
  Switch the power back on for electric models or turn the gas back on for gas models.
• Test the System:
  Run hot water through the system to ensure everything is working properly. Check for consistent water flow and temperature. If everything runs smoothly, your tankless water heater is now descaled and ready for use.

Maintenance Tips

• Check for Scale Regularly:
  If you live in an area with hard water, it’s a good idea to inspect your unit every 6-12 months for scale buildup.
• Consider a Water Softener:
  Installing a water softener can help reduce mineral buildup and decrease the frequency of descaling.

How Often to Descale a Tankless Water Heater

The frequency of descaling depends on the hardness of your water and your water heater’s usage. In areas with hard water, mineral deposits accumulate faster, making it necessary to do the cleaning process every 6 to 12 months. If your home uses a lot of hot water—for showers, laundry, and dishes—you may also need to descale more frequently to maintain efficiency.

For homes with soft or treated water, descaling might only be required every 12 to 18 months. Refer to your water heater’s user manual for manufacturer recommendations. Keeping an eye on performance indicators, like reduced water flow or unusual error codes, can help you decide when it’s time for maintenance. Regular checks ensure you won’t overlook this critical step.

Common Discaling Mistakes to Avoid

Descaling a tankless water heater is vital, but common errors can lead to damage or inefficiency.

One major mistake is using the wrong solution, as harsh chemicals may harm internal components. Always choose a descaling product made for tankless systems or use white vinegar.

Skipping the flushing step is another issue. Leftover cleaning solution can damage the system or affect water quality. Always rinse thoroughly with clean water after descaling.

Safety oversights, like failing to turn off the power or gas supply, are also dangerous. Ensure the unit is completely powered down before starting.

Lastly, always follow the manufacturer’s instructions to prevent mistakes that could void the warranty or damage the unit.

Conclusion

Regular descaling a tankless water heater is a simple yet critical step to maintain your heater’s performance, extend its life, and prevent costly repairs. By staying proactive with maintenance, you’ll ensure a consistent supply of hot water, lower energy bills, and a reliable system for years to come.

Don’t overlook this essential task—your tankless water heater depends on it!