Electric Tankless Water Heater Troubleshooting Ideas for Everyday Users

Electric Tankless Water Heater Troubleshooting

Electric Tankless Water Heater Troubleshooting

In this article, we are going to provide a step-by-step guide to assist electric tankless water heater troubleshooting.

Electric Tankless water heaters have heating elements for warming water, and some problems in their heating element can disrupt the normal water heating mechanism. There can also be many possible reasons for the improper functioning of the water heater other than bad heating elements such as a poor thermostat.

Common Problems with Electric Tankless Water Heater

It is necessary to believe that a tankless water heater does not work instantaneously as soon as you turn on the tap. A tankless water heater that has a recirculation pump can deliver hot water super-fast.

The timing to deliver hot water also depends on the length of the pipe. When there is a long pipe, cold water already present in it will be pushed away before hot water.

That’s not a big deal, and you don’t need to worry about it. But other major problems can also arise and these are listed below:

No Hot Water:


You got into the shower and waited longer than usual for hot water to come out of the tap but it proved to be a total waste. Due to issues in the heating system, tripping and, power shortage, no hot water will be available and these are the most common possible issues.

  • How to Fix:

If there’s no tripping in the breaker of the heater, just go for checking the limit of high temperature to reset it.

  • First, turn off breaker of water heater
  • Pull out the access panel of the heating element
  • Detach insulation, remove plastic safety guard and avoid touching any wire.
  • Push the red button
  • Cut off high-temperature reset button placed above the thermostat
  • Put back insulation, safety guard, and access panel.
  • Turn on the circuit breaker

Note: If this issue doesn’t resolve then it is better to replace the heating element.

Insufficient Hot Water (Coldwater sandwich/hot water temperatures fluctuates):

hot water temperatures fluctuates

If your electric tankless water heater is producing heat but that is insufficient to warm water then the reason for it can be a smaller unit to meet the usage demands. It should be kept in check that the usage demand never is more than the actual capacity of the water heater.

A Coldwater sandwich is something when you turn on the shower to get hot water but at first cold water comes out and after a few seconds hot water blast out. It was due to already trapped hot water in the pipe but again tap will release cold water.

There can also be many other reasons such as limescale & sediments buildup in the heat exchanger, plumbing crossover, and reduced flow of water due to clogged fixture aerator.

  • How to Fix:
  • If the temperature is set too low then try to increase the temperature up to 120-125 degrees Fahrenheit.
  • Check out if there is a single lever mixing valve installed then it can be the reason for plumbing crossover.
  • Try descaling and flushing out sediments or debris collected in the filter.
  • Clean out the venting system for the availability of fresh air for combustion.
  • The length of the venting pipe should be within limits, neither too short nor too long.

Too Much Water Temperature:

There comes another situation when too much hot water burst out of the shower. So you can’t take bath at this extreme temperature. Similarly, there are many causes of it like, reduced flow of water due to some coagulated substance stuck in the pipe, sediment buildup, and improper temperature sensor.

  • How to Fix:
  • Try to lower the temperature from too hot to a bearable range.
  • Clean the passageway for water in the pipe to avoid any obstruction in the smooth flow of water.
  • Clear out the fixtures
  • Descale or flush sediments and debris
  • Replace the broken temperature sensor with a new better one, or if it is misplaced then place it in its right position.

Electric Tankless Water Heater Troubleshooting related to Leakage:

Leakage of water is usually caused due to plumbing connections or leaking valves. Leakage in the water heater can lead to severe kind of damage in home so it is very necessary to fix it as soon as possible.

  • How to Fix:
  • A loose heating element or corrosion can cause leakage in the water heater, to avoid it tighten the heating element.
  • Check the bolts of the heating element, and tighten them, but be careful of over-tightening them.
  • Leakage in the storage tank can be due to corrosion, or bad O-rings. Keep extra O-rings to resolve this issue.

Rusty Water:


If the water coming out of the faucet is yellowish or dirty in color, it could be due to corrosion in the water heater, pipes, or filter. Anode rod in water heater prevents from rusting. If you’re getting rusty water then it means anode rods have been dissolved and you need to replace them.

You can check out this thread about is rusty water is safe for bathe or not.

  • How to Fix:

Remove collected water in pipe or filter to prevent further corrosion and it is better to replace a corroded water heater with a new one.

Foul Smell:

Due to the presence of some kind of bacteria produced in the filter, water comes out with a foul smell just like rotten eggs. Bad odor or rusty water can also be due to something growing in the unit.

  • How to Fix:

It is very important to keep it clean to avoid such issues in the future with your tankless water heater.

Flush your tankless water heater with vinegar and it is better to flush it after every six months.

Noisy Heater:

Is there any kind of noise coming out of your water heater? Like popping noise or low rumbling? Or a high-pitched sound? These sounds can be of boiling water. When there is an excessive buildup of sediments occurs in the heater they cause water to boil by exceeding temperature and results in this kind of sound.

  • How to Fix
  • To get rid of it, drain out all collected water in a pipe or filter through faucets.
  • Try to remove sediments and debris
  • Electric tankless water heaters are not that expensive so replace them if the issue continues.

Understanding Plumbing Crossover Problem:

  • Turn off cold water to the heater
  • Turn on all warm water taps
  • If after 10-12 minutes, there is still a flow of water, then your heater might have a plumbing crossover problem.

Error Codes:

Most electric tankless water heaters have a diagnostic system that includes a microprocessor or LCD screen to display any kind of error code due to some problems in the heater. The reason for the error code can be a spider web or air blockage.

It is possible to solve most of the problems associated with an electric tankless water heater with some right tools, but it is better to keep a valid warranty and functional unit to take help from a professional plumber.

  • How to Install an Electric Tankless Water Heater – Easy Steps
  • How to Size a Tankless Water Heater – For Small, Medium & Large Family
  • Easy Steps to Flush A Tankless Water Heater – Flushing Gas And Electrical Units
About Sami

Sami is also an Energy and Environmental Engineering graduate who has been working as a safety officer in a leading Fertilizer company for 18 months. He is also a graphic designer and marketing manager.

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