Troubleshooting Water Heaters: Common Problems and a Repair Guide

Plumbing tools to repair a water heaterImage by chiplanay from Pixabay

If you have no hot water in your home and wondering how to repair a water heater, this is an article you want to read.

The article is about troubleshooting water heaters, showing you how to repair common plumbing problems, including leaky water tank, no hot water, cold water sandwich, sediment and scale build-up, noise, element malfunctions, and others.

Troubleshooting water heaters: Common problems, causes, and symptoms

  1. Troubleshooting leaking
  2. How to fix condensation
  3. What to do if water is dripping?
  4. How to deal with the thermostat problems
  5. Troubleshooting sediment build-up
  6. How to eliminate discolored water
  7. What to do with corrosion?
  8. Why my water heater generates a rotten egg odor?
  9. What is water hammer and how to deal with it?
  10. Issues with heat traps
  11. Why my water heater is making a noise?
  12. Pilot light problems and repair tips
  13. Temperature fluctuation or cold water sandwich
  14. Is bulging storage tank dangerous?
  15. Flame issues
  16. Slow hot water delivery
  17. Plumbing crossover
Rheem gas water heaterRheem gas water heater
(photo: amazon)

This water heater troubleshooting guide contains a lot of information and can be used for repairing most of the electric and gas-powered units sold in the US and Canada, including; Rheem, AO Smith, Bradford White, American, State, GE, Ruud, Whirlpool, and 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 model can be applied to others.

To better understand propane, natural gas, and electric heaters, we recommend you become familiar with articles on how these units work and their 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 repair a water heater without calling a plumber.

Note: Any issues on plumbing, gas, and electricity should be performed by a qualified plumber or HVAC technician.

If looking for help and fast response, contact networx.com or homeadvisor.com and get Free Quotes from their reliable plumbing contractors.

Water heater troubleshooting tips

To make this 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. Some are found in this article, some in our articles about gas water heater problems, repairing electric type, or tankless. Check it out!

How to fix leaking

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

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

If there is a puddle of water on the floor your water heater might be leaking from the top or from the bottom connections.

How to prevent or repair water heater condensation

So, you have found a small puddle of water under the water heater and asking yourself - is the heater leaking, or the issue is with condensation? For the 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.

A 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 deal with it.

Dripping valves and fixtures

A 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 and 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 a thermostat and ensure a comfortable shower – again.

Sediment build-up

Check out this repair guide to fix the strange noise in the water heater and improve the lower performance. Sediment build-up at the bottom of the tank is the main problem 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.

How to repair a water heater and eliminate rotten egg odor

Smelly water, 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 and what you can do about it

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.

Heat traps issues

Heat traps are installed to increase the heater's energy efficiency, but you can remove them if they are the source of a problem. 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.

Fixing a noise problem

The water heater noise 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

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

Find out how to light a burner properly.

See what is happening when a green light on a gas control valve is flashing. and what to do.

Find a PRO to fix your pilot light issues.

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.

Storage tank bulging problem

Common symptoms seen on the heater exposed to 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. 

If your water heater is unrepairable, see how to dispose it of properly.

Burner flame issues

Improper gas combustion is dangerous. Is the burner flame yellow, orange, red and "lazy"? Do you experience slow hot water recovery, the burner doesn't ignite, 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 even more dangerous situation, check if there is carbon monoxide emission that might lead to gas poisoning.

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Slow hot water delivery

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

Plumbing crossover

Plumbing crossover is the main reason for complaints such as: “not enough hot water” and “hot water runs out quickly.”

Find out how to prevent, test, and repair it successfully.

Winterizing tankless

Is your tankless malfunctioning due to freezing temperatures? Use this article and see how to avoid the problem with proper winterizing.

AO Smith electric water heaterAO Smith electric water heater
(photo: amazon)

Proper diagnosis is crucial for the successful water heater repair

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

Before the big problem occurs, it is vital to understand 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 heaters is more complicated. Still, if you know the heating process, unit's anatomy and have basic knowledge, the repair shouldn't be a problem.

Due to the advanced design, tankless is even more complex. Because many models are equipped with the diagnostics system, troubleshooting is easier.

With the proper problem diagnosis, you will save time and money. I have often seen and experienced many times that a solution for a water heating problem can be very simple (like low-temperature settings or 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: More tips about troubleshooting

Preparing a site for the water heater repair

Before trying to fix any of the problems presented in the above text, 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 heater.
  • Shut off the water supply to the heater.
  • Plug the garden hose into the drain valve.
  • Prepare the necessary tools.


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 service, efficient, and safe operation.

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

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Common problems, how to troubleshoot and repair

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