How to Maintain a Tankless Water Heater

Tankless water heater
Tankless water heaters typically provide an endless supply of hot water, but not if maintenance is ignored. Keep your tankless hot water heater in great shape and protect your investment! Use the tips below to flush your tankless water heater and remove the lime scale.

The process of flushing the water heater is also known as descaling. This important part of tankless water heater maintenance should happen every six months to two years, depending on the hardness of your water. Just as your shower heads and sink aerators collect limescale, so does your tankless water heater. It’s important to remove this to prevent damaging the unit. Start by collecting the right supplies.

Supplies to Flush a Tankless Water Heater

  • Sump pump
    • Also called a submersible utility pump. 1/6 horsepower is ideal for descaling a tankless water heater. Be careful if you’re using a pump stronger than 1/4 HP.
  • Three gallons of white distilled vinegar
  • One five-gallon bucket
  • Two lengths of hose (2 ‒ 4 feet) with the necessary fittings
    • These should have been supplied with your unit. Otherwise, you can find them at your local hardware store. They look like washing machine water supply hoses.

How to Flush a Tankless Water Heater

  1. Set up your project.
    • Shut off the gas line or, if it’s electric, trip the circuit breaker.
    • Remove the access panel or cover, which is usually held in place by a few small screws or tabs.
    • Turn off the water supply, and release the pressure release valve.
  2. Hook up a hose to the inlet side of the hot water heater, which is where cold water enters the system. There should be a separate hose connection to do this, or you might have to remove the existing cold-water supply hose. Connect your small sump pump on the other end of this hose. Submerge the pump in a 5-gallon bucket filled with three gallons of white distilled vinegar.
  3. filled with vinegar. You’re creating a closed-loop system so the vinegar that enters the water heater exits back into the bucket before it is recirculated. If you’re using the existing hose’s connection rather than a separate connection for flushing, be sure to open the valve before you continue.
  4. Once the hoses are hooked up correctly, run the sump pump for one hour. The vinegar will work its way through the pipe system, removing lime scale and mineral buildup inside. After one hour, replace the vinegar with fresh water to remove any vinegar from the system.
  5. Once this is complete, shut off the pump, remove your flush hoses, and close the valves. Then re-attach the water hoses to the tankless water heater. Refer to the unit’s instruction manual for proper start-up procedures. This process usually begins with turning the water back on and then the unit’s gas or power.

How to Clean the Water Filter in Your Tankless Water Heater

Some tankless water heaters have a sediment screen to restrict larger debris before it reaches the heating unit. These sediment screens are typically usable for the life of the tankless heater and can be cleaned under running water or soaked in white vinegar until they are free of debris. The location of this filter depends on the make and model of your water heater; consult the manufacturer’s directions if you cannot find it.

Professional Tankless Water Heater Maintenance

Tankless hot water heaters can last decades if properly cared for. Regular maintenance is important to keep them running smoothly. If you find yourself too busy to flush your tankless water heater—or a little confused about it—Mr. Rooter® Plumbing can help.

Give us a call, or request an appointment online for water heater maintenance. If you live in an area with hard water, we recommend installing a water softener to prolong the life of all your plumbing appliances. We can help you make this decision!

This blog is made available by Mr. Rooter LLC, for educational purposes only to give the reader general information and a general understanding of the specific subject above. The blog should not be used as a substitute for a licensed plumbing professional in your state or region. Check with city and state laws before performing any household project.