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Troubleshooting Tankless Water Heaters

Do you have a tankless water heater and have questions about its performance?

One of the most common questions we receive is: “It doesn’t produce hot water instantly.” And in most cases, that’s true. Tankless water heaters aren’t designed to produce instantaneous hot water. Instead, they are designed to have an unlimited supply of hot water after the heated water makes it to the fixture where you’ve requested the water.

If you want instant hot water from a fixture, using a recirculation pump will solve the problem.

Other problems include:

No Hot Water

No matter how long you run the water, it never heats. Start by checking the electric power, gas, or water supply. Are they all working properly? Then check the shut-off valves; they might have been turned into the closed position.

Next, check the burner to make sure the flame rod generates sparks. You can also see if there is an error code present on the unit’s control panel.

Water is Too Hot

In most cases, the temperature is set too high. Turn down the temperature reading on the thermostat to avoid scalding.

It may also be water flow is being obstructed along its path. If the water isn’t mixing correctly to reach the desired temperature, you could be left with very hot water. Does the showerhead or fixture need cleaning? It may also be a sensor that is broken, incorrectly positioned, or loosened over time.

Water is Too Cold

Check to see what the temperature is set to – 125-130 F is a good temperature for most households.

It may also be a problem with the water line. Is the water filter or fixture clogged? Is the cold water not mixing properly with the hot? All can lead to creating a water flow that doesn’t reach your ideal temperature. It may also be a sediment or limescale build-up inside the heat exchanger. Flushing the system may be required.

Low Pressure

First, ensure the water pressure from the utility company is operating correctly. Then make sure there are no obstructions in the plumbing and fixtures. If you operate multiple fixtures at the same time, it can reduce the amount of pressure at each end location.


Tankless water heaters at some point may begin to make noise. Check the fan for debris. You can also check the burner to ensure it is still operating with a clear, light blue flame. Unstable flames may be caused by improper venting or a lack of gas pressure or combustible air.

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