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How to Service a Tankless Water Heater

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To keep your tankless water heater in good working order, performing preventative maintenance is a must. A tankless system can have a service life of 20+ years assuming it was properly cared for and installed.

The maintenance necessary for a tankless unit is entirely different to the maintenance tasks of a tank-style heater. And since gas vs electric tankless water heaters have very different designs, they also require different maintenance tasks. However, there is some overlap. 

Tankless Water Heater Preventative Maintenance

Water quality plays a critical role in the service life for tankless water heaters. Manufacturers rarely cover warranty issues that resulted from poor water quality. So being proactive can save you some money and a lot of headaches down the road.

These 3 proactive measures can make a huge impact on the service life of your tankless system:

  1. Install a Sediment Filter - These filters are installed on the incoming water line to the tankless. They filter out sediment and debris before the water reaches the unit.
  2. Regular Flushing - Limescale builds up within the tankless system and it reduces the unit's ability to heat water. Failure to flush limescale from the unit can result in costly repair bills, and a shorter service life.
  3. Install a Water Softener - If you live in an area that's prone to hard water, installing a water softener can help prevent limescale build-up from forming within your tankless system.


There are a number of important preventative maintenance tasks that should be performed on a tankless water heater. Of course, flushing the unit is likely the most important, but there are other things to consider as well. 

Most homeowners can perform many of the tasks, but if you own a gas unit, we highly recommend having it inspected annually by a professional.

You may want to consider hiring a professional the first time maintenance is needed. He can walk you thru what needs to be done for your specific unit, and you can ask questions, take notes and maybe even video some of the tasks. You'll know exactly what to do next time.

  • Always turn off the electrical power when you're working on the unit. Either unplug the unit or flip the circuit breaker off.
  • The water within the tankless can cause serious burns. Always use caution when handling VERY hot water.
  • Always check your owner's manual. The instructions below are to be used as a general guide, but your owner's manual will have the detailed information for your specific tankless unit. 

Preventative Maintenance Tasks

Both gas and electric water heaters need to be flushed on a regular basis. Although, we've mentioned this several times, we still want to stress how important it is to flush your tankless.

Electric Tankless Water Heaters

Beyond flushing, electric tankless water heaters require very little additional maintenance. Some manufacturers use an air filter that will need to be removed and cleaned periodically.

Without the occurrence of combustion, electric units run cleaner simply because there aren't any byproducts such as soot.  Combustion isn't needed to heat the water because the unit isn't "burning" the fuel.

Electric tankless systems have an entirely different design than gas units. Without the need for combustion to operate, they run cleaner, and cleaner means less preventative maintenance!

Gas Tankless Water Heaters

A gas tankless water heater requires more maintenance than an electric system. Keeping the burners, circulating air passages and control compartments free of dust and debris is critical.  These steps are easy to do and can be done as a stand alone project or along with other maintenance tasks.

General Cleaning Steps

  • Turn OFF the electrical power to the unit and allow the water inside to cool.
  • Turn OFF the gas supply.
  • Close the hot and cold water shut-off valves.
  • Remove the access panel and with a non-contact voltage tester, check that no electricity is reaching the unit.
  • Remove and clean the cold water inlet filter on the cold water line. Occasionally units have a filter on the hot water line, if yours does, it should be removed and cleaned.
  • Clear any dust from the main burner fan blades and heat exchanger using a can of compressed air. Never use a wet cloth or cleaners on or near the burner.
  • Wipe the cabinet with a soft, dry cloth.

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Annual Maintenance

  • Vents - Check the vent system for blockages or damage. Contact a licensed professional if you find an issue.
  • Motor Lubrication - Many manufacturers install permanently lubricated motors. Check your owner's manual.
  • Fan & Motor - Clean with a can of compressed air to remove any dirt and dust. (You may want to do this task more frequently).
  • Flame Inspection - The flame should be visually checked to verify proper operation. Look thru the view ports to check that the flame is stable and evenly covering the entire surface of the burner. It should be clear, and the color blue, without any yellow or orange. It's best to contact a professional to perform this task for you.
  • Pressure Relief Valve - Test the pressure relief valve to ensure it's in good repair and working properly. The water released thru the valve could be VERY hot, so use extreme care if you choose to do this task yourself. See caution box below.
Use Caution Testing the Pressure Relief Valve
  • The water that's released during this test may be VERY hot and under pressure. Severe burns may result.
  • Take precautions that the water discharged has an appropriate place to flow. It should never come in contact with your body or property. 
  • Snow Accumulation

    If you live in a cold climate that's prone to snow, pay special attention to the area around the flue terminal. It should always be free of snow and ice.

    If the air intake or exhaust is partially or entirely blocked the gas tankless water heater will not properly function.

    To learn more about cold weather precautions for tankless water heaters, read our full post.

    Coastal Areas

    Additional maintenance may be necessary if you live in a coastal area. Coastal regions are prone to airborne ocean salt, which can be very corrosive. .

    Consult your owner's manual or contact the manufacturer for specifics on for tankless water heater.


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