Rheem Tankless Water Heater Maintenance [Why+ How To Do]

The major Rheem tankless water heater maintenance procedures include:

  • Descale the heat exchanger.
  • Clean the combustion chamber.
  • Clean the air intake filter.
  • Check the gas pressure.
  • Monitor the water flow pressure.
  • Check operating temperature.

Also, cleaning the water inlet filter and inspecting the exhaust venting and neutralizer are also essential maintenance steps that you need to follow. 

rheem tankless water heater maintenance

Keep on reading our comprehensive guide to learn the step-by-step procedures to service your tankless water heater.

Quick Overview Of Rheem Tankless Water Heater Maintenance

All the manufacturers recommend maintaining the water heater in the perfect way to ensure the safety, efficiency, and longevity of the appliance. Also, routine maintenance of the water heater helps to prevent common heater problems and errors. 

rheem tankless water heater

First of all, you need to descale and flush your water heater to remove the build-up of calcium or lime deposits in the heating elements or pipes.

Next, clean out the combustion chamber and the related components like the burner, blower motor, flame rod, and igniter. You need to check for any electrical issues with these elements as well as cleaning. 

Besides all these, inspect and clean the air intake filter and water filter of your tankless water heater. Remove the filters from the connection and rinse them with clean water to remove any dirt particles. 

Plus, vacuum out the exhaust venting of your water heater as it may be contaminated with particles of dirt, pollens, and other foreign materials. 

Along with this, the routine Maintenance of condensate neutralizers is essential. Check operating temperature, water flow rate, and manifold gas pressure. 

Now, certainly, you are wondering about a well effective Rheem tankless water heater maintenance schedule. For this instance, you can do as follows:

Flush the water heaterOnce or twice a year.
Clean the combustion componentsOnce a year
Clean the air filter & water inlet filterEvery 3 to 4 weeks
Inspect the exhaust or venting Once a year. 
Neutralizer inspectionAnnually
Check the water flow & gas pressureEvery 6 months.
Check the operating temperature Regularly
Clean the outer area regularlyRegularly

Precaution Tips Before Performing The Maintenance

Maintenance of your tankless water heater is quite essential to ensure optimal performance. But as you are going to deal with an electric appliance, a certain degree of precaution is a must here that needs to apply. A single unconsciousness will lead to serious injuries or electrical hazards.

So, before heading to any of maintaining attempts to your tankless system, make sure you have performed the below 7 essential safety tips:

Tip #1: First of all, turn off your electric water heater. You can unplug the power cord from the electrical connection or turn the unit off from the main circuit breaker.

Tip #2: If it is gas –operated water heater, the next step would be to turn off the gas shut-off valve. The valve lever will be perpendicular to the gas lines. 

Tip #3: Turn off the water supply from the main shut-off valve.

Tip #4: Let your water heater cool before performing the maintenance, if you have just used it.

Tip #5: Avoid placing any combustible materials like gasoline containers, paint cans, paint thinners, and paper products nearby your water heater as it will lead to fire or explosion.  Store them in a safe place away from your water heater. 

Tip #6: Always keep your children away from the water heater. 

Tip #7: If you are suspecting a serious gas leak from the gas line, turn off your water heater and immediately contact a professional to handle the task.

11 Major Steps On How To Maintain A Tankless Water Heater

Here we’ve compiled an ultimate tankless water heater maintenance checklist to keep it in tip-top shape: 

1. Descale & Flush Your Water Heater

First, you need to concentrate on regularly flushing your tankless water heater system. While the heating process, the hard water passes through the heating elements. As well all know, hard water is high in dissolved minerals like calcium and magnesium.

descale & flush your water heater 

The heater components separate the minerals from the hard water, creating scale deposits that accumulate on the heat exchanger. The scale plugged up the heating elements making them less effective.

When this happens, it impacts the functionality and economy of the tankless system. So, it is recommended flush a water heater at least once a year at the minimum to keep it running smoothly.

How To Fix:

When the term comes about flush and descales a tankless water heater, it is a bit more challenging than a tank water heater. But no worry! Go through this comprehensive guide to learn how you will effectively flush your water heater like a professional!

2. Clean Out The Combustion Components

As with the descaling of the heat exchanger, it is recommended to check the combustion components on the regular basis. Higher chances are that the combustion chamber gets clogged with grim or foreign materials. 

If that is so, it reduces the ignition efficiency of the heater and you will not get your expected hot water. 

How To Fix:

Follow the below few phases to clean your heater’s combustion system:

Phase #1: Clean The Burner

First off, disconnect the cover panel from your tankless water heater front. Now locate and remove the screws that are holding the burner to the combustion chamber in place.

Detach the flame sensor and igniter wire from the assembly. When done, gently pull out the burner towards you and lay it on a flat surface. Now take an air compressor and blow out the stuck dirt and grim from the burner ribbons that are shown below.

stuck dirt and grim from the burner ribbons

When done, wipe down the ribbons with the microfiber cloth. Finally, reassemble the burner assembly back in place.

Phase #2: Clean The Clogged Combustion Fan

As with the burner assembly, the combustion fan is another essential part that pulls fresh air to the unit for ignition. You need to clean it as well. To do so, simply unscrew the GFCI mounting bracket plate and pull out the entire fan motor from the housing.

unscrew the GFCI mounting bracket plate

Now, take a brush and clean out the dirt and debris from the motor. Try to turn the motor with your finger to ensure it is moving freely. Plus, ensure a snug wiring connection of the blower Molex connectors with the PCB. 

3. Cleaning The Air Intake Filter

As with the water filter, it is essential to clean the air intake filter as well. It is the essential filter of your tankless water heater that keeps the bugs and dirt out of your system. 

air intake filter

As for always being in the contact with the dirt and grime, it gets plugged up and fails to continue its normal operation. To prevent this malfunction, you need to clean the air filter as well every three to four weeks.

How To Fix:

First off, take off the cover plate from the front place of your tankless water heater. Locate the air intake filter from the right/left corner of the heater. It may be attached with a screw. Unscrew it and pull out the filter toward you. 

Wash it out under the running water and remove the stuck grime and dirt from the filter screen. If needed, take a toothbrush and gently rub the screen for better cleaning. After cleanup, let it dry and reassemble it back in place. 

4. Water Inlet Filter Inspection

You will find a plastic knob figured water inter filter just next to the gas inlet valve at the bottom of your tankless water heater. It is used to regulate the water flow of the system to a minimum rate. At times the filter fills with debris and clogs, that require service. 

water inlet filter

That’s the reason, the manufacturer recommends checking and cleaning the water filter every month to maximize the continuous heating process. 

Wondering how to clean it? Follow the below section:

How To Do:

First, unscrew the water filter by turning it to the left counterclockwise. If needed, loosen the filter with a pair of pliers and remove it. Take a little container or jar while removing the filter from the connection. 

Now, take a Q-tip or toothpick and remove the stubborn dirt and particles that are caught in the filter screen.

Then, clean the water filter under water pressure. When done, reassemble it back in place and ensure a snug connection. 

5. Inspect The Igniter & Flame Sensor

There are a few flame rods or sensor in every gas-operated tankless water heater that monitor the presence of flame and ensures combustion. During the ignition process, the rods clog with the shoot that interrupts in sensing of the flame. 

igniter & flame sensor

As with the flame rod, the igniter is an essential part that ignites the fuel in the main burner area by generating a spark and continues to heat water.

You need to go through a regular inspection of these two essential elements and clean them properly. 

How To Fix:

First off, take off the front cover of your tankless unit and set it aside. Now remove the burner cover plate and inspect the igniter. You may pull out the burner assembly for better cleaning.

Now take a piece of fine sandpaper and start sanding the igniter and flame rods from the burner assembly. While cleaning, be careful not to damage the base or bend the wires.

clean the flame rods from the burner assembly

Check the electrical contact of the igniter and flame rods and all should be intact with the end of the ceramic probes. Also, check the flame rod and igniter for proper voltage and replace them if needed.

6. Inspect The Exhaust Or Venting

As with other above maintenance attempts, it is quite essential to inspect the exhaust or venting of your tankless system. All the tankless water heaters use a few vent pipes to continue the combustion process. 

Basically, during ignition, the combustion gases exhaust through the venting and the fresh air enters that helps to ignite the burner. Consequently, the water temperature starts raising. 

But at times, the venting pipes clog by dirt, debris, or insects that create blocks to entering the fresh air in the system. Also, carbon monoxide residue fails to escape into the unit. So, you need to inspect the venting and check for any blockages.

How To Fix:

  • To clean the venting, you will need a vacuum cleaner. 
  • Insert the extension hose through the venting port and vacuum out all the stuck dirt and debris.
  • If you are finding it hard to clean the unreachable area with the vacuum, take a duct cleaner and remove the dirt particles.  
  • Besides cleaning, ensure the proper installation of each venting pipe. 

7. Condensate Neutralizer Inspection

All water heaters equip a neutralizer that is installed in the condensate drain line. It is used to neutralize the condensate from the acidic water that forms in the heat exchanger of the water heater. 

Unlike other components, the condensate neutralizer of your tankless unit also needs to be routinely serviced to maintain the heater’s condensing efficiency. 

installed the condensate neutralizer drain line

As it is always in the contact with hard water, there form minerals in the pipeline block the neutralizer. In such cases, a blocked neutralizer creates an interruption in the continuous flow of water and the water temperature never reaches the set temperature.

So, you need to inspect this element annually for any blockages or damages.

How To Do:

Disconnect the front cover and locate the neutralizer from the inside of the unit. You will find two wires for the sensor on the top of the neutralizer. Make sure they are not wet. 

Now inspect the discharge port of the condensate at the bottom of the unit for any clog. It should go straight to the downward path as you can see in the picture below. 

discharge port of the condensate at the bottom of the unit

If you find any blockages, simply drain some water through the neutralizer to the service drain.  It will remove the clog through the plastic drainage tube at the bottom. Anyway, if you are dealing with a bad neutralizer, you need to replace it.

8. Maintain The Manifold Gas Pressure

If you have a gas-operated Rheem tankless water heater, gas flow is the major action here to heat the water. The gas pressure of the system is what pushes the water through the system. 

So, it is quite essential to maintain a proper gas pressure to keep the water flowing and to potentially meet the max demands on the unit. 

The minimum static gas pressure of a tankless water heater is 4.0″ W.C. for natural gas and 8.0″ W.C. for propane. The pressure below this amount will shut off the unit whereas too high pressure causes water leaks and many more malfunctions. 

Thus, manufacturers recommend testing gas pressure on a water heater on a regular basis. Here is how you will do so:

How To Test High & Low Gas Pressure On Tankless Water Heater?

There are a few ways to check the gas pressure of a water heater. Go through the below simplest ones:

test high & low gas pressure on tankless water heater

Step #1: Take a monometer, turn it on, and wait until it displays 0.00.

Step #2: Now attach the monometer tube to the manifold testing port. Turn on the water inlet valve. 

Step #3: Open all the hot water faucets to call for enough hot water demand. You will confirm it through the red burner light from the remote controller.  

Step #4: In this stage, remove the monometer tube from the monometer and block the tube end with your finger as in the picture below.

remove the monometer tube from the monometer and block the tube

Wait until the reading reaches 00. Reattach the tube.

Step #5: Now locate the PCB and find the manifold adjustment buttons. Press and hold the top and third buttons from the top until the LED of the remote control display 1L (minimum combustion) or 3H (maximum combustion).

locate the PCB and find the manifold adjustment buttons

Step #6: Go through the manual to check whether the reading meets the recommendations. If not, adjust the minimum manifold pressure to the standard pressure. 

To maintain the efficiency of a tankless water heater, it requires minimum water flow. The minimum water flow rate ranges from 2 – 5 gallons per minute. But the factor needs to be considered based on the tankless unit size and the hot water demand for your household. 

Whatever the fact is, you need to be always concerned about the flow rate whether it is meeting the minimum rate. If the water flow decreases in greater amounts, you will not get the hot water as expected. On the contrary, too high flow causes overheating. 

What To Do:

Below are the few essential steps that you need to follow to maintain the correct water flow:

i). Clean Out The Flow Sensor

There is a flow sensor inside of the unit which measures or regulates the presence of water flow and then initiates the heating process by sending a signal to the PCB. 

clean out the flow sensor

After long use, the sensor may be clogged by grim and particles, interrupting its normal functioning. So, it’s better to inspect the flow sensor and clean it.

To locate & clean the water flow sensor, follow the below steps:

  • First, head to the lower part of the unit and you will find a sensor attached just above the cold water connection.
  • Remove the little pin and disconnect the sensor from the connection using pliers.
  • Take compressed air and blow out the stuck grim inside of the sensor.  
  • When done, put the sensor back in place and ensure a secured concretion. 

ii). Check Water Pressure From The Water Line

Besides the flow sensor, you need to ensure the correct water pressure from the water lines as well. To do so:

  • Inspect the plumbing pipe and look for corrosion buildup in the water lines.
  • Locate aerators on the faucets and clean out the stuck debris from there.
  • Clean out the clogged cartridge of the faucets.
  • Increase the water pressure from the pressure regulator for the water lines.

10. Maintain The Proper Water Temperature

Though it may wonder you, checking and balancing out the operating temperature is also a good practice for water heater maintenance. You need to set and maintain the proper temperature of your tankless water heater system to get desired hot water without distraction.

Generally, you will find the 100°F default setting on the remote control display. It is recommended to set the water temperature at 120 degrees Fahrenheit. It will be best to maximize the heater’s efficiency. 

If you are setting the temperature too high, it will affect the water flow speed. Also, higher temperatures disconnect the heat exchanger thermistor from the PCB that stops heating the water to protect the venting material from damage. 

On the contrary, if the temperature is set too low, you will not only get lukewarm water but also it leads to bacterial growth that causes Legionnaires’ disease. So, it is essential to set the temperature within a specific range. 

11. Clean Out The Outer Area

As with the entire inside unit, you need to concentrate on cleaning the outer area of your tankless water heater. First, make sure you have turned off the electric supply to your water heater. 

Start with the exterior surface. Take a microfiber cloth and clean the cover panel of the unit. If there is a stuck grim, wipe it down with a clean damp rag. 

Then take off the heater access cover and wipe it as well. You can use a vacuum to remove dust. Or, if needed, use a small brush to clean more precisely. Don’t miss to clean the remote control as well. 

It’s better to clean the water heater’s exterior surface at least once or twice a week. 


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

The cost of flushing a water heater depends on the area and the quality of the plumber. If you want to descale your water heater, you will need an effective flush kit that generally costs between $100 and $200.

Should I use vinegar to descale a tankless water heater?

Yes! Despite using harsh chemicals, it is enough better to use vinegar to clean your tankless system. Just take 4 gallons or 15.1 liters of undiluted white vinegar and flush your water heater using it. 

Do all tankless water heaters require maintenance?

Yes! Whether it is gas operated or electric tankless water heater, it requires regular maintenance to prevent any problems and to keep it running fluently. 

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

If you don’t flush your tankless system, mineral deposits build up in greater amounts which prevents the unit from normal heating activity. At a time, the heater may stop working. 

In Bottom!

Well! That’s all from us here. Hope that there should be no queries left over on Rheem tankless water heater maintenance. Here we’ve well described each of the needed processes on how will maintain your tankless water heater system in a perfect schedule. 

Follow our guide and service your water heater according to our suggestions. Do let us know if you face any trouble while doing so. We are always ready for your assistance. 

About William

William is the founder of Fireplacehubs.com. He has real life practical skills in fixing smoker & heating appliance issues. He loves to share his knowledge & helps others in fixing their appliances & saving their money. William firmly believes that anyone can repair his or her unit with the correct guidance & knowledge. See more at about us.

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