How to Repair Tankless Water Heater: Become a Pro!

Tankless water heaters are a great investment for many homeowners, offering endless hot water and significant energy savings. However, like any appliance, they can experience issues from time to time. This article is aimed at guiding you on how to repair tankless water heater, address common problems and offer solutions.

7 Symptoms And Solutions – Repairing Tankless Water Heater

Below are the symptoms and possible solutions you can turn to if your tankless water heater is causing problems.

1. No Hot Water, or Lukewarm Water: Troubleshooting Common Flow and Temperature Issues

Having no hot water, or water that’s lukewarm at best, is a frustrating experience and a common issue with tankless water heaters. Before you resign yourself to a cold shower, let’s delve into the reasons behind this problem and explore potential solutions you can try.

Understanding Tankless Water Heater Operation:

Unlike traditional tank water heaters that store preheated water, tankless models heat water on demand as you turn on the hot water tap. This means the unit relies on several factors to deliver consistent hot water flow and temperature.

1. Exceeding the Flow Rate Capacity:

Tankless water heaters have a flow rate capacity, which refers to the amount of water they can heat per minute. If you’re running too many hot water appliances simultaneously, like the dishwasher, washing machine, and shower, the unit might not be able to keep up with the demand.

Solution: Identify the flow rate capacity of your tankless water heater (usually specified in gallons per minute or GPM) This information can be found in the user manual or on the unit’s label.

• Reduce Hot Water Usage: Be mindful of how many hot water appliances you’re using at once. Try staggering hot water usage or installing low-flow showerheads and faucets to decrease water demand and allow the tankless water heater to function optimally.
• Consider Multiple Units: If you have a large household with high hot water demand, explore the possibility of installing two or more tankless water heaters connected in parallel. This provides a higher combined flow rate to handle simultaneous hot water needs.
• Dedicated Units for Appliances: For appliances with high hot water usage, like washing machines or dishwashers, consider installing separate tankless water heaters specifically for those appliances. This frees up the main tankless unit to focus on providing hot water for faucets and showers.

2. Not Reaching Minimum Flow Rate:

Tankless water heaters require a minimum water flow rate to activate and begin heating. If the faucet isn’t turned on all the way, the flow rate might be insufficient for the unit to register a demand for hot water.

Solution:

• Open the Faucet Fully: Ensure the hot water tap is turned on completely to allow for the necessary flow rate. Once the faucet is fully open, the tankless water heater should activate and start heating the water.

3. Clogged Vents or Air Intake:

Proper ventilation is crucial for a tankless water heater’s efficient operation. Blocked vents or air intake channels can disrupt the combustion process and prevent the unit from reaching optimal operating temperature.

Solution:

• Inspect Vents and Air Intake: Locate the vents and air intake on your tankless water heater (consult the user manual if needed). Visually check for any obstructions like cobwebs, dust bunnies, or debris that might be blocking airflow.
• Clear Blockages: Carefully remove any obstructions from the vents and air intake channels. Some tankless water heater models might have filters on the air intake that require periodic cleaning according to the manufacturer’s instructions.

4. Power Source Issues:

For Electric Tankless Water Heaters:

Check the Circuit Breaker: If your tankless water heater is electric, a tripped circuit breaker could be interrupting power supply. Locate your main electrical panel and check if the breaker for the tankless water heater has flipped to the “off” position. 

Reset the breaker if tripped, but if it trips again repeatedly, consult a qualified electrician to identify the underlying cause.

For Gas Tankless Water Heaters:

Gas Valve and Supply: Verify that the gas valve on the tankless water heater is fully open, allowing gas flow to the unit. Additionally, ensure there’s sufficient gas pressure in the line. If you use propane, check the tank level to ensure it’s not empty.

5. Frozen Pipes (Cold Weather Only):

In freezing winter temperatures, water pipes can freeze and prevent hot water from reaching your taps.

Solution:

Thaw Pipes Safely: If you suspect frozen pipes, avoid using methods that could damage the plumbing system. Instead, use safe thawing methods like applying heat lamps or towels soaked in warm water to the affected areas. Once the pipes thaw, your hot water flow should resume.

Additional Considerations:

If you’ve checked all the above and your tankless water heater still isn’t delivering hot water, there could be other factors at play. These might include:

• Faulty Igniter (Gas Models): If your tankless water heater uses gas and won’t ignite, there might be an issue with the igniter component. This is a repair best left to a qualified gas appliance technician.
• Faulty Heating Element (Electric Models Only): In electric tankless water heaters, a malfunctioning heating element can prevent proper water heating. This component requires replacement by a qualified electrician to ensure safety and proper functionality.

Remember: While troubleshooting these initial steps might be possible for DIY enthusiasts, for any repairs involving electrical components, gas lines, or complex internal components, it’s crucial to prioritize safety. Don’t hesitate to call a qualified plumber or gas appliance technician to diagnose and fix the problem if you’re unsure about any steps.

2. Your House Temperature is Too High!

If your water is scalding, here’s how to fix it:

• Reduce Hot Water Usage: Using multiple taps simultaneously can overload the system. Reduce hot water usage until the temperature regulates.
• Adjust Thermostat: Lower the water heater thermostat to a comfortable setting, typically around 120°F (48°C).
• Reposition Temperature Sensor: The sensor might be malfunctioning due to incorrect placement. Consult the manual and reposition it for a more accurate reading.
• Clean Inlet Filter: A clogged inlet filter can restrict water flow, causing overheating. Follow the manufacturer’s instructions on cleaning the filter for your specific model. Important: Always turn off and cool down the unit before performing any maintenance.
• Clear Blockages: Reduced water flow due to blockages can also lead to overheating. Check for and remove any blockages in the pipes or unit.
• Faulty Heating Element (Electric Models Only): A faulty heating element in an electric tankless water heater can malfunction and stay on constantly, overheating the water. This might require replacing the element by a qualified professional.

3. Build up of Mineral or Sediment in Water Heater

Over time, mineral buildup from hard water or sediment buildup from rusty pipes can clog your tankless water heater. This can affect water pressure, temperature, and even become a safety hazard.

How to Repair Tankless Water Heater: In such cases, it’s recommended to call a professional plumbing company like JMK Plumbing to descale and flush your system. Regular annual maintenance, including flushing, can help prevent such problems.

4. Water Switching Between Hot And Cold Quickly

This unpleasant surprise is known as the “cold water sandwich” and is more common in showers. Here’s why it happens:

Previous Hot Water Usage: Someone might have used hot water just before you, leaving residual hot water in the pipes. This initial hot water is followed by cold water as the tankless heater catches up to heat water specifically for your shower.

How to Repair Tankless Water Heater: If this is a frequent annoyance, consider installing a mini-tank water heater. This small tank can provide hot water while the tankless unit heats up, eliminating the cold water sandwich effect.

5. Smelly or Discolored Water

Clean, clear water is what you should expect. If your water is discolored or smells foul, you might have bacteria or mold growth inside the unit.

Rotten Egg Smell: The most common culprit is sulfate bacteria thriving in warm water left stagnant in the tank. This issue usually occurs with traditional tank water heaters, but can also happen in tankless units if not properly maintained.

How to Repair Tankless Water Heater: Regularly flushing your tankless water heater with a descaling solution or white vinegar can help prevent this problem. However, if the smell persists, the tank might be too contaminated and require replacement. Avoid DIY methods like draining and refilling, as the smell is likely to return.

6. Ignition Issues in Your Gas Tankless Water Heater

For a proper gas ignition, several factors need to be considered:

Gas Pressure: Ensure the gas valve is open and there’s sufficient gas pressure. Check your gas bill and ensure it’s paid.

Check Components and Sensors: Inspect wires, fuses, and electrical components for signs of damage or burnout. Ensure there’s no condensation or debris on the burners that might hinder ignition.

Error Codes: Some tankless water heater brands display specific error codes for ignition failures. Consult your user manual to identify the code and its corresponding troubleshooting steps. Here are some common examples:

• Takagi: Error Code 111, 11, or 3
• Rinnai (Electric): Error Code 11
• Navien: Error Code E003
• Noritz: Error Code 11

General Troubleshooting: 

Here are some additional checks to perform:

• Gas and Electricity: Verify that both gas and electricity (if applicable) are turned on and supplying power to the unit.
• Gas Type: Ensure you’re using the correct gas type (natural gas or propane) for your specific model.
• Gas Pressure: Confirm that the gas pressure meets the manufacturer’s specifications.
• Air Purging: After installation or if the gas line has been serviced, ensure all air has been properly purged from the line.
• Plumbing Installation: Verify that the plumbing is installed correctly, following both local codes and the manufacturer’s instructions.
• Water Pressure: Check that the water pressure falls within the recommended range for your tankless water heater.
• Water Hardness: Extremely hard water (over 7 grains per gallon) can lead to sediment buildup and hinder performance. Consider a water softener if necessary.
• High Altitude: If you’re located at a higher altitude, consult the manual to see if your water heater needs specific adjustments for optimal operation.

Important Note: While some basic troubleshooting steps can be attempted for a gas tankless water heater not igniting, it’s crucial to emphasize safety. If you’re not comfortable with these checks or suspect a more complex issue, it’s best to contact a qualified gas appliance technician to diagnose and repair the problem. They can ensure the unit is operating safely and efficiently.

7. A Leaking Tankless Water Heater!

Leaks on a tankless water heater are typically caused by faulty valves or loose plumbing connections. Here’s how to address a leak:

Identify the Source: Try to locate the origin of the leak within the plumbing pipes. If you can’t pinpoint it readily, shut off the water supply to your tankless water heater and call a local plumber for inspection and repair.

Safety First: Remember, dealing with gas and water requires caution. If you’re unsure about any troubleshooting steps or suspect a major issue, don’t hesitate to call a qualified professional to ensure your safety and the proper functioning of your tankless water heater.

Useful Tips for Tankless Water Heater Repair

While the previous sections covered common tankless water heater problems and their solutions, some situations might require a more nuanced approach. Here’s a breakdown of additional factors to consider:

Brand-Specific Issues:

This guide addressed general troubleshooting steps. However, certain tankless water heater brands might have specific quirks or error codes. It’s always recommended to consult your user manual for detailed troubleshooting instructions specific to your model.

For example, the section on gas tankless water heater ignition mentioned error codes for some popular brands like Takagi, Rinnai, Navien, and Noritz. Your user manual will provide a more comprehensive list of error codes and their corresponding meanings for your specific brand and model.

DIY vs. Professional Repair:

While some troubleshooting steps can be performed by homeowners who are comfortable with basic plumbing and electrical tasks, it’s crucial to prioritize safety. For tasks involving gas lines, electrical components, or complex repairs, it’s best to call a qualified plumber or technician. They have the expertise and experience to diagnose and fix the problem efficiently and safely.

Preventative Maintenance:

Regular maintenance is vital for keeping your tankless water heater functioning optimally and preventing problems down the road. Here are some key maintenance tips:

• Annual Flushing: Schedule a professional annual flushing to remove mineral buildup and sediment that can impede performance and efficiency.
• Filter Cleaning: Clean or replace the inlet filter regularly according to the manufacturer’s instructions. This prevents debris from restricting water flow and potentially causing overheating.
• Visual Inspection: Periodically perform a visual inspection of your tankless water heater for any signs of leaks, corrosion, or loose connections. Address any minor issues promptly to prevent them from escalating into bigger problems.

Considering Replacement:

Tankless water heaters, like any appliance, have a lifespan. Most models last around 10-15 years with proper maintenance. If your tankless water heater is nearing the end of its lifespan or experiencing frequent repairs, it might be more cost-effective to consider a replacement.

Consult a qualified plumber who can assess your unit’s condition, recommend suitable replacement options based on your hot water needs and budget, and ensure proper installation.

The Final Word

That was everything you needed to know about how to repair tankless water heater. These heaters offer numerous benefits, but like any appliance, they require occasional maintenance and repairs. By understanding common problems, potential solutions, and the importance of professional help when needed, you can ensure your tankless water heater continues to provide you with endless hot water for years to come.

You can contact JMK plumbing if you’re facing water heater issues. Our technicians will visit your place and address the issue quickly.