Fix Tankless Heater

A tankless water heater, also known as an on-demand water heater, can be a fantastic addition to any home. Offering endless hot water and energy savings compared to traditional tank heaters, they're a modern convenience many homeowners appreciate. However, like any appliance, tankless water heaters can experience problems. Troubleshooting and fixing these issues yourself can save you money on plumber bills and restore hot water quickly. This guide provides a comprehensive overview of common tankless water heater problems, troubleshooting steps, and potential DIY fixes. Remember, safety is paramount. If you are uncomfortable with any of these steps, consulting a qualified plumber is always the best option.

Understanding Tankless Water Heater Basics

Before diving into troubleshooting, it's crucial to understand how a tankless water heater works. Unlike traditional tank heaters that store and heat a large volume of water, tankless heaters heat water only when needed. When a hot water tap is turned on, cold water flows through a heat exchanger inside the unit. A powerful burner or electric element heats the water, delivering hot water on demand. Once the tap is turned off, the heater shuts off, saving energy by not continuously heating water.

Key Components of a Tankless Water Heater

• Heat Exchanger: The core component responsible for heating the water. Made of copper or stainless steel, it efficiently transfers heat from the burner/element to the water.
• Burner/Electric Element: The heat source. Gas-powered units use a burner, while electric units use an electric element.
• Flow Sensor: Detects when water is flowing, triggering the heating process.
• Control Board: The "brain" of the unit, controlling all operations based on sensor readings and user settings.
• Igniter: For gas units, the igniter starts the burner.
• Temperature Sensor: Monitors the water temperature, ensuring it reaches the setpoint.
• Vent System: Exhausts combustion gases (for gas units) safely outside.

Common Tankless Water Heater Problems and Troubleshooting

Tankless water heaters, despite their efficiency, can encounter several common issues. Identifying the problem is the first step toward finding a solution.

1. No Hot Water

Symptoms: Turning on the hot water tap results in only cold water.

Possible Causes:

• No Power: Check the circuit breaker (for electric units) or gas supply (for gas units). Ensure the unit is turned on.
• Tripped High-Limit Switch: Some units have a high-limit switch that trips if the unit overheats. Reset the switch (refer to the manufacturer's manual).
• Flow Sensor Issue: The flow sensor might be malfunctioning, failing to detect water flow and preventing the unit from firing up.
• Igniter Problem (Gas Units): The igniter might be faulty, preventing the burner from igniting.
• Control Board Failure: A damaged control board can prevent the unit from operating correctly.

Troubleshooting Steps:

1. Check Power/Gas Supply: Ensure the unit is receiving power or gas.
2. Reset High-Limit Switch: If applicable, locate and reset the high-limit switch.
3. Check Error Codes: Consult the unit's manual for error codes that can pinpoint the problem.
4. Inspect Flow Sensor: Examine the flow sensor for debris or damage. (This may require disassembling parts of the unit, proceed with caution or consult a professional)

Example: John's electric tankless water heater suddenly stopped producing hot water. He checked the circuit breaker and found it tripped. After resetting the breaker, the heater worked perfectly. This simple check saved him a service call.

2. Lukewarm Water

Symptoms: The water is not as hot as desired, even at the highest temperature setting.

Possible Causes:

• Incorrect Temperature Setting: Verify the temperature setting on the unit.
• Incoming Water Temperature: Extremely cold incoming water can impact the unit's ability to heat the water to the desired temperature.
• Overload: Trying to run too many hot water appliances simultaneously can exceed the unit's capacity.
• Scale Buildup: Mineral scale inside the heat exchanger can reduce its efficiency.
• Gas Pressure Issues (Gas Units): Insufficient gas pressure can prevent the burner from producing enough heat.

Troubleshooting Steps:

1. Adjust Temperature Setting: Increase the temperature setting on the unit.
2. Reduce Hot Water Demand: Avoid running multiple hot water appliances at the same time.
3. Descale the Unit: Regularly descale the unit to remove mineral buildup (see section below).
4. Check Gas Pressure (Gas Units): A qualified technician should check the gas pressure.

Tip: During winter, incoming water temperatures are lower, requiring the tankless heater to work harder. Consider slightly increasing the temperature setting during colder months.

3. Fluctuating Water Temperature

Symptoms: The water temperature alternates between hot and cold.

Possible Causes:

• Low Water Flow: Insufficient water flow can cause the unit to cycle on and off.
• Air in the Water Lines: Air pockets can disrupt the flow of water.
• Scale Buildup: Similar to lukewarm water issues, scale can cause inconsistent heating.
• Minimum Flow Rate Not Met: Tankless heaters require a minimum flow rate to activate.

Troubleshooting Steps:

1. Increase Water Flow: Ensure the hot water tap is fully open.
2. Purge Air from Lines: Run all hot water taps for a few minutes to remove air pockets.
3. Descale the Unit: Remove mineral buildup.
4. Check Minimum Flow Rate: Consult the unit's manual for the minimum flow rate requirement.

Actionable Advice: Regularly flush your tankless water heater to prevent scale buildup and maintain consistent water temperature. This simple maintenance task can significantly extend the life of your unit.

4. Error Codes Displayed

Symptoms: The unit displays an error code on its control panel.

Possible Causes:

• Error codes are specific to each manufacturer and model, indicating various problems.

Troubleshooting Steps:

1. Consult the Manual: Refer to the unit's manual to identify the meaning of the error code and recommended solutions.
2. Restart the Unit: Sometimes, simply restarting the unit can clear the error code.

Research: According to a study by the Department of Energy, regular maintenance, including addressing error codes promptly, can improve the efficiency and lifespan of tankless water heaters by up to 20% [¹].

5. Leaks

Symptoms: Water leaking from the unit or surrounding connections.

Possible Causes:

• Loose Connections: Fittings and connections might be loose.
• Corrosion: Corrosion can damage components, leading to leaks.
• Damaged Heat Exchanger: A cracked heat exchanger can cause leaks.
• Pressure Relief Valve (PRV) Leak: The PRV might be leaking due to excessive pressure.

Troubleshooting Steps:

1. Inspect Connections: Check all connections for leaks and tighten if necessary.
2. Inspect for Corrosion: Look for signs of corrosion and replace corroded components.
3. Check PRV: If the PRV is leaking, have a plumber inspect the system pressure.

Caution: If you suspect a leaking heat exchanger, contact a qualified plumber immediately. Replacing a heat exchanger is a complex and expensive repair.

Descaling Your Tankless Water Heater

Mineral scale buildup is a common problem in tankless water heaters, especially in areas with hard water. Scale reduces the unit's efficiency and can lead to various problems. Descaling involves flushing the unit with a descaling solution to remove mineral deposits.

Descaling Procedure:

1. Gather Supplies: You'll need a descaling solution (specifically designed for tankless water heaters), a submersible pump, two hoses, and a bucket.
2. Turn Off Power and Gas: Disconnect the power and gas supply to the unit.
3. Isolate the Unit: Close the isolation valves (if installed) on the cold and hot water lines. If you don't have isolation valves, you'll need to shut off the main water supply.
4. Connect Hoses: Connect one hose from the cold water isolation valve (or cold water inlet) to the submersible pump in the bucket. Connect the other hose from the hot water isolation valve (or hot water outlet) back into the bucket.
5. Add Descaling Solution: Fill the bucket with the descaling solution and water, following the manufacturer's instructions.
6. Circulate Solution: Plug in the submersible pump and let the solution circulate through the unit for the recommended time (typically 30-60 minutes).
7. Flush with Water: After descaling, flush the unit with clean water for several minutes to remove any remaining descaling solution.
8. Reconnect and Restore: Reconnect the water and power/gas supply to the unit.

Practical Example: Sarah noticed her tankless water heater was producing lukewarm water, and she suspected scale buildup. She followed the descaling procedure outlined above and was amazed at the amount of mineral deposits that flushed out. After descaling, her water heater worked like new.

Preventative Maintenance for Tankless Water Heaters

Regular maintenance is crucial for extending the life of your tankless water heater and preventing problems. Here are some key maintenance tasks:

• Annual Descaling: Descale the unit at least once a year, or more frequently if you have hard water.
• Inspect Vent System (Gas Units): Check the vent system for obstructions or damage.
• Clean Air Filter (If Applicable): Some models have an air filter that needs to be cleaned regularly.
• Check Water Pressure: Ensure the water pressure is within the recommended range.
• Professional Inspection: Schedule a professional inspection every few years to identify potential problems early.

When to Call a Plumber

While many tankless water heater problems can be resolved with DIY troubleshooting, some issues require the expertise of a qualified plumber. Call a plumber if:

• You are uncomfortable working with gas or electricity.
• You suspect a gas leak.
• You cannot identify the cause of the problem.
• The problem involves complex repairs, such as replacing a heat exchanger or control board.
• You are unsure about any step in the troubleshooting or repair process.

Conclusion

Tankless water heaters offer numerous benefits, but they require proper maintenance and occasional troubleshooting. By understanding the basics of how they work, recognizing common problems, and following the troubleshooting steps outlined in this guide, you can often resolve issues yourself and save money on costly repairs. Regular descaling and preventative maintenance are crucial for extending the life of your unit and ensuring consistent hot water. However, always prioritize safety and don't hesitate to call a qualified plumber when needed. Now that you're armed with this knowledge, take the next step and schedule a descaling or inspection to keep your tankless water heater running smoothly for years to come. Consider creating a maintenance calendar to remind yourself of these important tasks!

¹ U.S. Department of Energy. (n.d.). *Tankless Water Heaters*. Retrieved from [https://www.energy.gov/energysaver/water-heaters/tankless-water-heaters](https://www.energy.gov/energysaver/water-heaters/tankless-water-heaters)