Why Your Tankless Water Heater Has No Hot Water

Why is your water heater not working?

Troubleshooting Guide: Why Your Tankless Water Heater Isn't Working

Tankless water heaters have gained immense popularity for their energy efficiency and endless hot water supply. However, like any other appliance, they can encounter issues that may lead to a lack of hot water. Here are some common reasons why your tankless water heater might not be working and how you can troubleshoot these problems.

1. No Power Supply

The first thing you should check is whether your tankless water heater is receiving power. Check the circuit breaker to ensure it hasn't tripped. If it has, reset it and see if the heater starts working again. If it continues to trip, there might be an underlying electrical issue that requires professional attention.

2. Ignition Failure

Tankless water heaters rely on ignition to heat water on demand. If the ignition fails, you'll be left with cold water. This could be due to a variety of reasons such as a faulty igniter, gas supply issues, or a dirty burner. In such cases, it's best to consult a professional technician to diagnose and fix the problem.

3. Gas Supply Problems

If you have a gas-powered tankless water heater, ensure that the gas supply is uninterrupted. Check the gas valve to make sure it's fully open. Additionally, inspect the gas lines for any leaks or obstructions that might be preventing the heater from igniting.

4. Water Pressure Fluctuations

Inconsistent water pressure can lead to problems with tankless water heaters. It's crucial to ensure that the water pressure in your home is within the recommended range specified by the manufacturer. High or low water pressure can cause the heater to malfunction or shut off completely.

5. Mineral Buildup and Scaling

Hard water deposits can accumulate inside the heat exchanger of your tankless water heater over time, reducing its efficiency. This can lead to a decrease in the amount of hot water produced or even complete failure. Regular maintenance, including descaling, is essential to keep the heater functioning optimally.

6. Improper Ventilation

Tankless water heaters require proper ventilation to operate efficiently and safely. If the venting system is blocked or improperly installed, it can lead to issues such as overheating or shutdown. Make sure the venting system is clear of any obstructions and that it complies with the manufacturer's specifications.

7. Freezing Temperatures

If your tankless water heater is located in an area susceptible to freezing temperatures, it may be equipped with a freeze protection feature. However, if this feature malfunctions or if the unit is not properly insulated, freezing can lead to damage. Ensure that your heater is installed correctly and consider additional insulation if necessary.


A tankless water heater not working can be frustrating, but with a systematic approach, you can often identify and address the issue. Remember to consult the manufacturer's manual for specific troubleshooting steps and, when in doubt, seek the assistance of a qualified technician. Regular maintenance and prompt attention to any problems will help ensure your tankless water heater provides reliable hot water for years to come.

For more information about tankless water heaters or see if you can get a rebate through your utility, visit our web page or call 1-800-818-4298.