Guide to Tankless Water Heater Maintenance

Last Updated On June 22, 2024

Updated on July 11, 2022



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tankless water heater maintenance

Tankless water heaters don’t require as much maintenance as storage tank water heaters. However, they still require maintenance to remove sediment buildup in the unit and keep the hot water heater running properly. 

If you upgrade to a tankless unit, you need to know how to care for it properly with this guide to tankless water heater maintenance. 

In this PlumbingNav guide, we will cover: 

  • Why is tankless water heater maintenance necessary?
  • When does your tankless hot water heater need maintenance? 
  • Tankless water heater maintenance supplies
  • How to perform tankless water heater maintenance

What's In This Guide?

      Why Is Tankless Hot Water Heater Maintenance Important? 

      How important really is tankless water heater maintenance? As it turns out, maintenance to a tankless hot water system plays a large role in how it works and how much you get out of it. 

      Longevity of Heater

      Tankless water heaters can last up to 20 years, significantly longer than a tank-style water heater. However, without maintenance, your tankless water heater may expire prematurely

      Proper Function of Components

      Limescale buildup left behind inside of the water heater can damage the components inside of the device, in particular the heat exchanger, heating elements, and gas burner.

      Hard water, in particular, contains high mineral levels. When the water heats up, calcium deposits form. These deposits will cover the thermostat to the point that it can’t correctly register the water temperature, forcing the device to suddenly produce scalding hot water


      The increased temperatures force the device to work harder, bringing down the energy efficiency of the device. If your device runs less efficiently than it should, you will end up paying for it in higher utility bills.

      Hot Water Production

      If the tankless system becomes clogged, it can also affect the flow rate or how much hot water it can produce. If the gallons per minute (GPM) generation doesn’t meet your household’s needs, it may create a cold water sandwich. A cold water sandwich means that you will get hot water surrounded by moments of cold water.

      When Does Your Tankless Water Heater Need Maintenance? 

      As a general rule, we suggest performing maintenance on your tankless heater once a year before the weather starts to turn cold. 

      Different manufacturers may suggest performing maintenance more frequently or less frequently than most, so always go by the manufacturer’s recommendation. 

      Cost of Tankless Water Heater Maintenance

      You have the option to enlist the services of a professional plumber, but that can get expensive. 

      The average hourly rate for a plumber comes to $30 – $40 an hour, so they usually charge $50 – $100 per hour for labor. Expect to pay for two hours of service. You’ll also need to pay for the service itself, usually an additional $50 – $100. 

      You can expect your final bill to fall anywhere between $150 – $300. 

      Supplies You’ll Need For Tankless Water Heater Maintenance

      You can do the work yourself, but you want to set yourself up correctly so that you don’t run into any problems along the way. 

      Supplies you will need include: 

      • Submersible pump
      • Hose
      • 3 – 5 gallon bucket
      • Plumber’s tape 
      • Vinegar

      Buying the Right Circulation Pump

      You can rely on a recirculation pump in a tankless water heater flush kit to provide enough power to complete the job. 

      If you use an existing sump pump, you want it to produce at least 3/16 hp of power. You also need it to be a submersible sump pump that won’t experience damage or create a dangerous situation when you place it into water.

      did you know tankless water heater maintenance tips

      How To Do Tankless Water Heater Maintenance (5 Steps)

      Step 1: Safety First!

      Before you get started, turn off the fuel source of the water heater.

      If you have a gas tankless water heater, it will either use natural gas or propane. Shut off the gas valve. 

      To shut off power to an electric tankless water heater, shut off the power at the circuit box.

      Step 2: Perform a Visual Inspection

      You need to open up the water heater at this point to perform a visual inspection. Look for signs of corrosion and leakage on the casing as well as on the inside.

      Corrosion refers to the natural deterioration of metal, and you may notice rust on the valves or the casing of the water heater. 

      The rust can get into the water, lowering the quality. If too much rust gets into the water, it presents a health risk. 

      A tankless device doesn’t have an anode rod to absorb corrosive materials, but a storage tank does. Without the anode rod to assist with corrosion prevention, this means that the valves may become even more susceptible to corrosion. 

      Corrosion may lead to leaks. If you notice a leak, see if it happens at the top of the device or the bottom of the device. You must replace the corroded valves or get a water heater repair before moving on, or it will continue to waste water and cause water damage.

      Step 3: Flush Water Heater

      The most important part of performing tankless water heater maintenance is to flush the water heater. 

      To flush the water heater correctly, you need a tankless water heater flush kit. The kit usually comes with a bucket, a 3/16 hp tank, and two hoses. 

      Remove the hose attached to the cold water supply line and replace it with your new hose. Attach the other end to the pump to create a circular motion of water. 

      You will put the pump into the bucket, filled with a mixture of vinegar and water (1 part vinegar to 2 parts water)

      When submerged, let the pump recirculate the water for an hour to allow the vinegar to run through the unit and clean out the scale deposits. Some high-end flush kits can get the job done in even less time for people in a hurry. 

      When finished, reattach the original cold water supply line. 

      Step 4: Clean Filter

      Some tankless water heaters have a water filter attached to the cold water inlet that collects sediment before it gets inside of the device. 

      If you have a filter, you simply remove it and clean it by running it under a faucet.

      Not all models contain a filter. Check your user manual to learn the specifics about your water heater. 

      Step 5: Tighten All Connections

      Tighten every connection on your demand water heater. 

      Some of the valves to examine include:

      • gas valve
      • pressure relief valve
      • drain valve
      • isolation valve

      You can also use plumbing tape to provide additional reinforcement. 

      Step 6: Monitor Results

      Restore power to your water heater and allow it to run as usual. This is a good time to confirm your tankless unit is set to the right temperature.

      Examine any reports generated by your water heater and monitor if the cleaning improved the unit’s performance by comparing usage one month from the next.

      FAQs for Tankless Water Heater Maintenance

      How often does a tankless water heater need to be serviced?

      Service your tankless water heater annually. 

      Are tankless water heaters a lot of maintenance?

      No, tankless water heaters do not require much maintenance, especially compared to storage tank units. 

      What happens if you don’t flush your tankless water heater?

      If you don’t flush your tankless water, the heater may expire prematurely, produce unhealthy water, lower the device’s flow rate, and run less efficiently. 

      How much does it cost to service a tankless water heater?

      Expect to pay $150 – $300  per hour for professional tankless water heater maintenance. 

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      About Plumbing Navigator

      We write about "all things plumbing," helping you navigate common questions, repairs, and the best plumbing products on the market.

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      We write about “all things plumbing,” helping you navigate common questions, repairs, and the best plumbing products on the market.

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