AO Smith Water Heater E55 Code

AO Smith Water Heater E55 Code [How To Fix]

This troubleshooting guide will disclose the meaning of the error code ‘E55’ on AO Smith Water Heater. Plus, you will learn how to clear the error message from the controller display of your water heater. So, keep reading till the end. 

Table of Contents

What Does E55 Mean On AO Smith Electric Water Heater?

Error code ‘e55’ on AO Smith Water Heater indicates your water heater senses a water leak. 

Generally, if the water makes its way into the wiring of the unit from the installation process, the water heater will pop this error code on the display. On the other hand, a water leak may be common if it’s an old unit. In this case, water may leak from the top, bottom, or side of the unit. 

But what if the error code ‘e55’ appears when it’s a brand new installation and there is no leak? 

Well, the water heater will continue to display that error code as it’s sensing the unit is not full and it takes more times than usual to be full. 

Common Places To Look For A Water Leak On Your AO Smith Water Heater

A water heater generally leaks from these places of the unit: 

Leaking From Drain Valve

Drain valve is a common location from where the water leaks. The water will leak out of the drain valve if you fail to close it tightly. Besides, water will continually come out of the valve if it gets broken. 

How To Fix: 

Start with checking the drain valve to ensure you close it fully. If not, use a flat head screwdriver to tight the closed position. 

If the water leak persists after closing the drain valve fully, you should replace the drain valve to stop the leakage.  

And here is the step-by-step guide you should follow to change the drain valve like a pro: 

  • Shut off the power to the unit by flipping the circuit breaker.
  • Close the water inlet valve. 
  • Attach a garden hose to the drain valve at the bottom of the unit and place the other end of the hose to your nearest floor drain or outdoor. 
  • Open the drain valve using a flat head screwdriver and let all the water drain out of the tank. You can make the draining faster by opening a hot water faucet.
  • Now, use an adjustable wrench and turn the drain-valve counterclockwise to unthread the valve. 
  • Install a new drain-valve and tighten it up and verify you fully close the drain valve. 
  • Next, open the water intake valve to allow the tank to refill. 
  • Finally, restore power to the unit. 

T&P Valve Leaking

Water Leak From T&P Valve

Too high water pressure is the main culprit that causes a small amount of water to leak from the Temperature and Pressure Relief Valve. 

On the other hand, if you see a large amount of water coming out of the T&P discharge pipe, it may be due to the overheated tank. 

In some rare cases, the T&P Valve will get clogged by debris and cause the water to drip. Thermal expansion is another reason for a leaking T&P Valve. 

How To Fix: 

If the T&P Valve drips water due to high water pressure, I recommend you install a pressure reducing valve on the cold water supply line. Then, adjust the PRV pressure between 50 to 60 PSI. 

Secondly, you shouldn’t operate the unit if the T&P valve is leaking because of an overheated tank. Otherwise, it may explode the tank. It will be better to call a qualified plumber to handle this T&P Valve issue. 

And lastly, inspect the T&P valve for a clog and release the blockage by manually operating the valve. 

Leak From Piping On The Inlet And The Outlet

It is common for the water heater to leak if you install it in a warm or humid location. In this case, condensation can accumulate and run down flue tubes, cold water supply lines, and other piping connections.  

How To Fix: 

Check every water heater piping connection for a leak. If needed, tighten up those connections to stop water leakage. 

Heating Elements Leaking

Heating element is another component on an electric water heater from where the water leaks out. Basically, the heating element leaks when its gasket gets torn or damaged. 

How To Fix: 

Just replace the gasket of the heating element and it will stop the water leak. Also, don’t forget to reseal the element threads. 

How To Fix AO Smith Water Heater E55 Code?

Now, let’s walk through the following steps to clear the error code e55 from the display: 

1. Flip the breaker to the off position to shut off the electric supply to your water heater.

2. Inspect all the electric connections and wiring to see whether they get wet or not during the installation process. 

3. Check for plumbing leaks and fix them. Generally, an electric water heater leaks water out of the drain valve, T&P valve, leaks from piping on the inlet and the outlet, and heating elements. Luckily, I mentioned the way of fixing those leaks. So, follow the guideline and stop the leakage. 

4. Don’t forget to check the entire water tank. If the water is coming out of the tank, there is no option except replacing the water heater with a new one. 

5. Once you stop the water leakage, reset your AO Smith Water Heater, which will clear the error code ‘e55’ from the display. To reset the unit, follow the below procedure step-by-step: 

  • Shut off electric power to the unit.
  • Remove the upper access panel using a flat head screwdriver and gently pull out the insulation. 
  • Once you slide away the upper access panel and the insulation, it will expose a red reset button. 
  • Press the reset button and it will make a click, which will reset the unit. 
  • Put both the insulation and the upper access panel back into their place. 
  • Restore power to your water heater.   


The diagnostic code ‘E55’ on AO Smith water heater means the unit senses a water leak. In this regard, check the water leak suspicion areas I mentioned. Once you locate the leak source, fix it and reset the water heater. I hope it will clear the fault code. 

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