Tankless Water Heater Too Hot or Too Cold


Is your tankless water heater making your shower water too hot or too cold? Try these simple fixes.

If your shower is too hot

  • Be sure that the tankless water heater's thermostat is turned down to its lowest setting.

  • Clean the system’s inlet filter. Follow the manufacturer’s instructions for your model. IMPORTANT: Whichever type of tankless water heater you own, turn off the unit and wait until it cools down before attempting any DIY work on the system.

  • Tighten the heater’s temperature sensors.

If it's too cold

  • Check your gas pressure and gas supply line.

  • Water-saving devices may restrict the flow of water so that it’s below the minimum required for your tankless heater to function. Clean and descale any low-flow showerheads and aerators. If this doesn’t solve the problem, consider replacing them.

In general, getting a comfortable mix of cold and hot water can be challenging with a tankless water heater. The best way to do it is to first turn on the hot water, and then slowly turn on the cold water. My former home had tankless hot water, and you only had to turn the cold water faucet about a centimeter for the perfect shower temperature -- one millimeter more and the water went cold.

When you need a professional

For more information about your water heater, check out our article Common Problems with Tankless Water Heaters.

If you’re still having trouble with your tankless water heater, call a licensed plumber to take care of it.

Photo credit: Caryn Colgan/Sean Geiger for Networx.com.

This post was updated November 7, 2017.

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