Rheem tankless water heater maintenance: Cleaning and Flushing

Learn how to perform Rheem tankless water heater maintenance by cleaning and descaling.


If you own a Rheem tankless water heater, you’ve made a wise choice for an efficient and continuous hot water supply. To keep your Rheem tankless water heater operating at its best and to ensure its longevity, regular maintenance is essential. In this comprehensive guide, we will walk you through

  • Rheem tankless water heater maintenance schedule,
  • Step-by-step procedure for servicing your unit, by cleaning, flushing, and descaling.
  • Important safety guidelines to follow.

Rheem Tankless Water Heater Maintenance Schedule

Before we dive into the maintenance procedures, let’s discuss how often you should maintain your Rheem tankless water heater. Generally, it is recommended to perform maintenance at least once a year. However, if you live in an area with hard water or your unit is subject to heavy usage, more frequent maintenance may be required. Regular maintenance helps prevent issues and ensures the efficient performance of your water heater.

Keeping your Rheem tankless water heater in top-notch condition requires following a maintenance schedule to ensure it runs smoothly and efficiently. Some parts need frequent attention, while others only require yearly checks. Here’s a breakdown of the inspection schedule and what to check or do at each interval:

Daily Inspection:

  • Check the Condensate Drain Line: Ensure that the condensate drain line is free from clogs and blockages. A clear drain line ensures the smooth flow of condensation from the unit.
  • Monitor the Air Filter: Regularly check the air filter to ensure it is clean and functioning properly. A clean air filter ensures that your tankless water heater works efficiently without any interruptions in combution and ignition.

Monthly Maintenance:

  • Complete Water Heater Drainage: Once a month, it’s essential to drain the heater completely. This helps remove any accumulated sediment or debris inside the unit, maintaining its performance.

Annual Maintenance:

  • Examine the Water Filter: Annually, inspect and clean the water filter to prevent any debris from entering the unit and affecting its efficiency.
  • Inspect the Air Intake Filter: Check the air intake filter for dust or dirt build-up. Cleaning or replacing it as needed ensures proper air circulation for optimal performance.
  • Check the Burner: Inspect the burner for any signs of dirt or corrosion. Keeping it clean ensures efficient heating.
  • Inspect the Venting System: Ensure the venting system is free from obstructions or blockages. Proper venting is vital for safe operation.
  • Test the Pressure Release Valve: Verify that the pressure release valve is working correctly. This valve helps release excess pressure and ensures safety.

Step-by-Step Procedure for Rheem Tankless Water Heater Maintenance

Now, let’s walk through the step-by-step process of servicing your Rheem tankless water heater:

a. Turn Off the Power and Water Supply:

Before you begin, turn off the power to the water heater at the circuit breaker and shut off the water supply until we mention to turn them on.

b. Clean the exterior, remote and Surrounding areas

  1. Clear the Surroundings: Before you begin, ensure the area around the water heater is clutter-free. Remove any items, debris, or dust that may have accumulated around the unit.
  2. Vacuum Away Dirt and Debris: Use a vacuum cleaner with a soft brush attachment to gently remove dirt, dust, and lint from the exterior of the water heater. Pay special attention to the vent openings and any visible vents on the unit.
  3. Wipe the Access Cover Panel: Carefully open the access cover panel of the water heater. Use a soft microfiber cloth to wipe away any dirt or dust that may have collected on the panel. This ensures that the components inside the panel remain clean and free from obstructions.
  4. Clean the Remote Control: If your water heater has a remote control, don’t forget to give it some attention too. Use a soft damp cloth to gently wipe the remote, removing any smudges or dirt that may have accumulated.
  5. Allow Surfaces to Dry: Once you’ve completed the cleaning process, give the water heater surfaces some time to air dry naturally. Avoid using excessive moisture or harsh chemicals that may damage the unit.

c. Inspect and Clean the Air filter

rheem tankless water heater air filter location and its cleaning

  1. Locate the Air Filter: The air filter is typically located on the top of the water heater. Remove the access panel and look towards the top and gently remove the air filter from its position.
  2. Wash the Air Filter: Take the air filter look for any accumulated dirt, dust, and debris. You can use a soft brush to carefully scrub the filter, ensuring that all particles are thoroughly removed.
  3. Rinse and Dry: After cleaning the air filter, rinse it thoroughly with mild detergent and water to ensure there is no residue left behind. Once rinsed, allow the filter to air dry completely. Make sure it is fully dry before proceeding to the next step.
  4. Reinstall the Air Filter: Once the air filter is dry, reinsert it back into its original position on the water heater. Ensure it is properly aligned and securely in place.

d. Drain the Water Heater:

Draining your tankless water heater is a straightforward process that ensures the removal of any accumulated sediment and helps maintain its efficiency. Follow these simple steps to drain the water heater:

  1. Shut Off the Gas Valve: Begin by setting the gas shut-off valve to the closed position. This step is crucial to ensure safety during the draining process.
  2. Run Hot Water Faucets: Turn on all the hot water faucets in your home to let the water run until it turns cold. Once the water from the faucets is cold, turn them off.
  3. Close the Cold Water Shut-Off Valve: Locate the cold water shut-off valve and turn it off. This valve stops the flow of water into the water heater, allowing you to drain it.
  4. Attach a Garden Hose: Take a garden hose and attach it to the drain valve located in the hot water outlet line of the water heater. Securely connect the other end of the hose to the nearest floor drain or an appropriate drainage point.
  5. Drain the Water: Open the drain valve and let the water flow out through the garden hose. Allow the water to drain completely until no more water is coming out.
  6. Detach the Garden Hose: Once you’ve drained every last drop of water, carefully detach the garden hose from the drain valve. Make sure the drain valve is securely closed.

e. Clean the Water Filter:

After draining all the water from your tankless water heater, it’s time to clean the water filter for optimal performance. Follow these steps to clean and reinstall the water filter:

Rheem tankless water heater cold water inlet filter location

  1. Remove the Water Filter: Unscrew the water filter from the base of the cold water inlet line and carefully with the help of pliers and slide it out of the line.
  2. Wash the Water Filter: Take the water filter to your sink and wash it with water. Use a soft brush to gently remove any sediment buildups or debris.
  3. Reinstall the Water Filter: Once the water filter is clean, put it back into its place on the cold water inlet line. Tighten it up until it fits snugly, ensuring a secure fit. Be careful not to over-tighten the water filter, as it may cause damage or deformation.

f. Check the Venting System:

Annual inspection of the venting system is crucial for your Rheem tankless water heater’s smooth operation. Verify that all vent sections and connections are secure and airtight. If the venting system becomes clogged, carbon residue may not properly exit your home, potentially leading to issues.

If you’re not comfortable inspecting the venting system yourself, I highly recommend hiring a certified plumber for the job. Their expertise ensures a thorough examination and any necessary maintenance.

g. Perform a System Flush:

Flushing your Rheem tankless water heater is a crucial maintenance task to ensure optimal performance and longevity. Over time, mineral deposits, sediment, and debris can build up inside the unit, affecting its efficiency. Flushing helps remove these impurities and keeps your water heater running smoothly. Here’s a step-by-step guide on how to flush your Rheem tankless water heater:

rheem tankless water heater flushing process

  1. Gather the Necessary Tools and Materials: Before you start, ensure you have all the required tools and materials. You’ll need a Rheem tankless water heater flush kit(or distilled white vinegar 3 or 4 gallons), a 5 gallon bucket, a submersible pump or a small condensate pump, and a two hoses.
  2. Connect the Pump and Hose: After completely draining the water, take a submersible pump and connect it to the water heater’s cool water drain valve using a hose. Make sure the hose is securely attached.
  3. Flush the Heater: Connect another hose to the hot water drain valveand place its end into the bucket. Fill the bucket with a cleaning solution recommended by the manufacturer or white vinegar. Turn on the pump to circulate the cleaning solution through the system. This step helps dissolve mineral deposits and scale inside the heater.
  4. Rinse the Water Heater: After flushing, disconnect the pump and all hoses and close the drain valves. Next, Flush the water heater with clean water to rinse out any remaining cleaning solution and debris. To do this  Allow the water to flow through the system for a few minutes, connect the garden hose like we did for draining and turn on the cold water supply.
  5. Reconnect Gas Supply: Once the water heater is thoroughly rinsed, Remove the garden hose and close the drain valve. Then, turn on the gas supply to the water heater.
  6. Restore Power: Finally, turn on the power supply to the water heater from the circuit breaker.

h. Inspect the Burners and Igniter:

Inspecting the water heater burner annually is essential for ensuring its proper operation and efficiency. Here’s a step-by-step guide on how to inspect the burner:

  1. Turn on a Hot Water Faucet: To create demand for hot water, turn on a hot water faucet in your home. This step is crucial as it activates the water heater to operate.
  2. Inspect the Burner Light: Look through the burner sight glass while the water heater is running. Observe the burner operation and flame appearance. A properly functioning burner should have a steady blue flame. If you notice any irregularities in the burner’s operation or if the flame is not blue, it indicates a potential issue.
  3. Addressing Unusual Burner Operation: If you observe any unusual burner operation or a non-blue flame, it’s essential to take prompt action. As dealing with burners requires expertise, We highly recommend hiring a professional plumber or technician to address the problem. They can accurately diagnose the issue and either repair or replace the burner assembly as needed.

Failing in burning and ingnition can lead to code 11, refer How to fix Rheem tankless water heater code 11

i. Check for water Leaks:

Inspect all connections and joints for any signs of leaks. If you find any, tighten the connections or replace damaged parts. For more detailed article on leaks refer: Rheem water heater leaking from top or bottom

Safety Guidelines for Rheem Tankless Water Heater Maintenance

While performing maintenance on your Rheem tankless water heater, safety should be your top priority. Here are some important safety guidelines to follow:

a. Always turn off the power and water supply to the water heater before starting any maintenance procedures.

b. Use proper safety equipment, such as gloves and eye protection, when handling cleaning solutions or performing any maintenance tasks.

c. If you are unsure or uncomfortable with any maintenance procedures, it is best to seek professional help. A certified technician can ensure that the maintenance is done correctly and safely.

d. Follow the manufacturer’s guidelines and recommendations for maintenance, as outlined in the Rheem tankless water heater user manual.

Related article: Rheem water heater pilot light won’t stay lit

By following this comprehensive guide, you can ensure that your Rheem tankless water heater continues to provide efficient and reliable hot water for years to come. Regular maintenance will not only prevent potential issues but also extend the life of your water heater, saving you time and money in the long run. So, get started with your Rheem tankless water heater maintenance and enjoy the benefits of a well-maintained and high-performing water heater in your home.

Joseph Miller

Joseph Miller is a highly experienced water heater repair expert with a passion for keeping homes warm and comfortable. With over 50 years of industry expertise, Joseph has developed a deep understanding of water heater systems and the intricacies of their repair and maintenance.

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