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How to Perform Annual Inspection & Maintenance on Your Rinnai Tankless Water Heater

One of the most important ways to protect the investment of your tankless water heater is to perform annual inspection and maintenance.

One of the most important ways to protect the investment of your tankless water heater is to perform annual inspection and maintenance. Skipping annual maintenance is the number one cause of premature failure, and you could also void the warranty. Proper inspection and maintenance will help you get the highest efficiency and longest life of your heater. Read on to learn how to perform annual maintenance on your Rinnai tankless water heater.

Annual Inspection Steps

1. Check for Error Codes

The first step in performing an annual inspection on your Rinnai tankless water heater is to check the error-code history. This will let you know if something happened to trigger an error code that you may not be aware of. Here is how you check the error code history:

  1. Push the Hot Water power button
  2. Push the down-arrow button

After you have done that, the unit will show you if there have been any error codes. This will look like an "e" and then the code number in the display on the unit. If there are no error codes, then you can move on to the next step.

2. Remove the front panel of the water heater

Removing the front panel of your water heater is easy, but you must be careful to do it properly to avoid damaging the tabs holding it on.

  1. Remove side-panel strips

There are two aesthetic strips on either side of the front panel. To remove them, push the left side strip straight to the left and then push the right side strip straight to the right.

2. Remove the 4 panel screws

After you have removed the panel strips, there are 4 screws that need to be removed. Once you have done that, the front panel is ready to be removed. Do this by tilting the bottom forward and lifting it off. Once again, never try to force the panel off because you risk damaging the tabs that hold it in place.

3. Inspect the Flame Rod

Now that the front panel is off, we can visualize the burner to make sure that the flame rod is operating properly.

You will notice a sight glass that allows you to peer through it to see tubes inside that are diffusing fire. What you want to see is a very clean blue flame coming out of the flame rod into the heat-exchanger area, where water is heated as it passes through.

The whole heat-exchanger area is going to glow like a red flame, and this is exactly what you want to see. But you also want to see a clean blue flame radiating underneath the heat-exchanger. This tells you that the gas pressure is proper and exactly how it should be.

4. Remove and clean the air filter screen

Because there is a fresh air intake on your Rinnai tankless water heater, there is a screen to prevent bugs and debris from entering your unit.

The air filter is located at the top right corner of your unit and will slide out towards you. Check it for removable items and then replace it.

We do this because, if there is obstructing debris in the air filter, it could cause your unit to not have the proper air-gas mixture. This can cause it to not work properly. You should check the air filter at least once a year.

5. Remove and clean the cold water filter & flush heater with vinegar

Below the unit, you will notice a series of pipes and valves. For this step, we are concerned with the water inlet and outlet pipes, which are the two inside pipes going up into the unit.

1. Turn off both the cold and hot water domestic water valves

If you follow those two inside pipes, you will come to a double-valve assembly. Shut both of these valves off to prevent water from flowing in or out of the heater, thus isolating it so you can clean the cold water filter.

2. Remove the cold water valve cap

Although you have shut off the water intake valve, there will still be a few quarts of water left in the unit. Remove the cold water valve cap in front of the double-valve assembly on the cold water intake pipe. Have a bucket ready to catch the water that will empty out of the unit, a few quarts at most, and turn the blue valve leading to the cold water cap.

3. Remove the cold water filter

Where the cold water intake pipe meets your unit, there is a cold water filter. We need to inspect and clean this filter for any debris that may be affecting the performance of your unit.

Unscrew the cold water filter and inspect it for debris or residue. If you find any, simply clean it out with a brush and run it under some cold water. Then, reinsert the filter back in.

*Note: When reinserting the filter, you should feel the o-ring seat. That is how you will know it is sealed and tight enough. Finger-tight is adequate.

4. Turn intake and outlet valve back on

Replace the cold water valve cap if you have not done so already and shut off the blue valve leading to it. Then, turn both the cold water intake valve and the hot water outlet valve back to the on position to flow water back into and out of your unit.

5. Flush heater with vinegar

If you haven’t already, connect service hoses to the hot and cold water lines. Shut off the hot and cold water valves to the heater, and turn on the valves to the service lines. Pour out the water from the heater into a 5-gallon bucket, and wait about 5 minutes for all the water to drain.

Next, pour 2-3 gallons of vinegar into a 5-gallon pail that contains a sump pump. Connect the hose from the cold water inlet valve to the sump pump. Set the sump pump into the vinegar. Turn the hot and cold water valves on the service lines to the on position. Turn on the sump pump, and let the vinegar cycle through the heater, and let the vinegar drain back into the 5-gallon bucket. Cycle the vinegar through the system for about 30 minutes.

Then, turn the cold water service valve off, and disconnect the hose. Turn the main cold water valve on. This will cycle cold water through the unit and rinse the pipes of any vinegar. The system cycle for about 5-10 minutes to ensure all vinegar is removed.

Turn the hot water service valve off, and remove the hose. Replace caps on both hot and cold service ports. Turn the hot and cold main water lines to the on position.

Next, turn the heater back on.

6. Replace the front panel

Finally, to finish your annual inspection, you need to replace the front panel of your unit. Start by putting the front cover back in place and inserting the four screws you removed. Tighten those and then replace the side strips on both sides.

Congratulations, you have completed the annual maintenance of your Rinnai tankless water heater!

If any of these steps are confusing, call us or send us a picture with your questions and we’ll answer them.

Check out these videos below for a close-up look inspection and maintenance of your Rinnai tankless water heater.

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