Troubleshooting Water Heaters
Problems and Repair Guide
(updated 2019)

Troubleshooting water heaters and a repair guide.

Explore common heating problems, causes, symptoms, and tips on how to fix: leaky water tank, no hot water, not enough hot water, cold water sandwich, sediment, and scale build-up, noise, bad odor, gas valve problems, pilot, thermocouple and other water heating issues.

DIY instructions and how to get help! 

In this article:

  1. Leaking
  2.  Condensation
  3.  Dripping
  4.  Thermostat problems
  5.  Sediment build-up
  6.  Discolored water
  7.  Corrosion
  8.  Rotten egg odor
  9.  Water hammer
  10.  Heat traps
  11.  Noise
  12.  Pilot light problems
  13.  Cold water sandwich
  14.  Bulging
  15.  Flame issues
  16. Slow hot water delivery
Rheem gas water heaterRheem gas water heater

A troubleshooting guide can be used for repairing most of the electric and gas-powered water heaters sold in the US and Canada, including; Rheem, AO Smith, Bradford White, American, State, GE, Ruud, Whirlpool, others.

Keep in mind that symptoms or signs of water heater failure are very similar among different manufacturers, and many are the same, so directions for one brand and model can be applied to others.

To have a better understanding of propane, natural gas, and electric heaters, we recommend you become familiar with articles on how these units work and its main parts. Once you collect all the necessary information, troubleshooting water heaters become much easier.

Heater's problems are not complicated to diagnose, and if DIY home and plumbing projects are not strange to you, and you have the necessary tools, skills, and the right guide, then you can successfully troubleshoot the water heater, without calling an expensive plumber.

Note: Troubleshooting water heaters that are using gas and electricity should be performed by a qualified individual, plumber, or HVAC technician.

If looking for help and fast response, contact and get 3 Free Quotes from their proven plumbing contractors.

Common problems, causes and symptoms

To make the hot water heater troubleshooting guide easier to understand and fix the heater as a pro, we have provided a lot of information about common problems, causes, and symptoms of water heating issues.

Water heater leaking

A leaky water heater is the most frequent problem reported by many people and is found in many consumer reports. The reasons for such malfunction might be that the steel body of the storage tank has corroded up to that level that caused a rupture on the tank, resulting in a water leak.

Another reason is the water discharge due to overheating from the temperature and pressure relief valve (TPR).

If there is a puddle of water on the floor and you know that the leak is coming from the top, check out this article, and if you know that the water is dripping from the bottom, then do this.

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You have found a small puddle of water under the water heater - is the heater leaking, or is it condensation? For proper troubleshooting, keep in mind that condensation is often present on newer models, such as condensing models, as these units are more efficient than older ones.

The typical heater will produce approximately one-half gallon of water vapor during every hour of work. Condensation usually happens shortly after the heater starts. Follow the provided link to learn more about what causes condensation, how to prevent, and how to deal with it.

Dripping valves and fixtures

Puddle of water under the tank-type water heater is often related to water leaking and condensation. But what if there is dripping from the relief valve or a fixture, during the unit's recovery cycle, when no hot or cold water is used. Find out what causes dripping and how to fix it.

Thermostat problems

If the water is too hot or cold, you might have a problem with the faulty thermostat. Use this article to learn how to troubleshoot and replace the water heater thermostat and ensure a comfortable shower – again.

Sediment build-up

Check out this troubleshooting guide to fix the strange noise in the water heater and improve the lower performance. Sediment and lime build-up at the bottom of the tank are the main problems that must be addressed correctly and on time. Also, learn how to reduce the effects of hard water using a water softener.

Discolored water

There are a few reasons why your hot water is discolored, has a milky or rusty appearance, and the anode rod is one of them.


Explore what causes corrosion and how to prevent it, so rust doesn't pollute hot water and weakens the structure of the heating system.

Rotten egg odor

Smelly water, which is also known as sulfur or rotten egg odor, is generated by bacteria due to decomposing sacrificial anode inside the tank.

Find out how to eliminate bacteria from the system using the chlorination procedure. Water heaters that are not equipped with the anode or include powered rods do not have such a problem. See how to fix smelly water.

Water hammer

Water hammer is the hydraulic shock that is loud and destructive to the house plumbing and a heater. Fixing this common plumbing problem is relatively easy. Learn how.

Heat traps issues

Heat traps are installed to increase the energy efficiency of the unit, but if they are the source of a problem, you can remove them. Since the sound problems such as ticking, clicking, humming or tapping, are often caused by the heat traps, this guide can help you install or remove them.

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The noise inside the water heater is usually associated with two main conditions; water hammer and mineral build-up, but there are also other reasons such as pounding, rumbling, crackling, popping, ticking, and sizzling.

Pilot light problem

"Pilot light goes out", or pilot outage is one of the most common issues when operating gas-fired water heaters. As improper venting is one of the main causes, see what you can do about it; how to prevent and fix the problem.

Cold water sandwich

What to do when the temperature fluctuates from hot to cold and from hot to cold? Check out this guide for an easy fix and comfortable shower with less "cold water sandwich" effect.


Common symptoms that are seen on the heater that is exposed to the excessive pressure are cockeyed nipples of the top of the heater and bulged or reversed bottom of the head. See what can be done about the bulging problem and how to prevent it.

Burner flame issues

Improper gas combustion is dangerous. Is the burner flame yellow and "lazy"? Do you experience slow hot water recovery, the burner doesn't ignite, there is combustion odor, smoking and sooting, or burner flame floats.

Then, check out the article "how to properly vent a gas water heater" and learn how to fix it. To avoid an even more dangerous situation, check if there is carbon monoxide emission that might lead to gas poisoning?

Slow hot water delivery

Does it take too long to get hot water at the kitchen sink or in the bathroom? Check out what is the cause and what you can do to get hot water faster.

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Winterizing tankless

Tankless water heater malfunction due to freezing temperatures? Use this article and see how to avoid the problem with the proper winterizing.

AO Smith electric water heaterAO Smith electric water heater

The first thing when dealing with the electric or gas hot water heater troubleshooting is to recognize a problem.

Before the big problem occurs it is vital to understand what are the symptoms, does a heater have low performance, uncomfortable temperature, is it still efficient, does it deliver enough hot water, is it heating water at all, and finally troubleshoot and fix it on time.

Electric models are very easy to troubleshoot while fixing gas heater is more complicated, but if you know the heating process, unit's anatomy and have basic knowledge, the repair shouldn't be a problem. Tankless, due to the advanced design is even more complex, but since many models are equipped with the diagnostics system, troubleshooting gets easier.

With the proper problem diagnosing you will save time and money. I have seen and experienced many times that a solution for water heating problem can be very simple (like a blown fuse at the breaker), or easy repair by replacing the faulty element (heating element, thermostat...).

The recommendation is to perform the maintenance and service the unit regularly, because this is one of the best ways to prevent the problem on the heater, and even extend the life of the unit.

YouTube video 1: Troubleshooting Gas Water Heaters

YouTube video 2: How to Troubleshoot an Electric Water Heater

Preparing site for troubleshooting

Before trying to fix any of the problems shown above, here are more tips for troubleshooting water heaters and preparing the site for repairs.

  • Turn off both gas and electric power before working on the heaters.
  • Shut off the water supply to the heater.
  • Plug the garden hose to drain valve.
  • Prepare the necessary tools for service.


Keep in mind that the water heater failure and the unit's replacement can be easily avoided if the signs of a potential problem are identified on time.

Some of these issues are easy to fix; some require more time, knowledge, and the right tools. Prevention is the key, so if the maintenance is done regularly and as recommended by the manufacturer, it will bring long term, efficient, and safe operation.

For the additional help use the AO Smith website with the links to the service handbooks (in pdf format).

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Solar water heating troubleshooting guide
Gas water heater troubleshooting
Electric water heater repair

› Troubleshooting guide

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