DIY Gas Water Heater Repair Guide: Tips and Tricks for Homeowners

Are you experiencing issues with your gas water heater?

Don’t worry, you’re not alone.

Our gas water heater repair guide is here to help homeowners deal with the most common problems related to pilot lights, thermocouples, gas valves, and other gas-related components.

(photo: pixabay)

You’ll learn about the frequent causes, symptoms, and solutions to these issues, and we’ll provide you with step-by-step instructions to fix them yourself.

However, before you begin any repair work, it’s important to remember that leaking propane and natural gas can be dangerous. Natural gas tends to rise while propane, being heavier than air, collects at floor level.

Safety should always be your top priority when working with gas appliances.

What You Need to Know Before Attempting Gas Water Heater Repair: Common Problems

  1. Safety first
  2. How does a gas water heater work
  3. Problem #1: No hot water
  4. Problem #2: Lack of oxygen
  5. Problem #3: Sooting
  6. Problem #4: Condensation
  7. Problem #5: A burner won’t stay lit
  8. Problem #6: A pilot won’t light or stay on
  9. Problem #7: Corrosion
  10. FAQ

Safety First

Whether your gas water heater is working or not, , if you detect a gas leak, immediately turn off the pilot light, shut the main gas valve, and DO NOT switch on any electrical power.

Call a plumber or your gas supplier immediately from a remote location, such as outside, as any spark could be dangerous.

I smell gas” – you would say… but that doesn’t mean there is a problem.

Natural gas is odorless, and the scent you detect is added as a safety measure for easy identification of potential leaks without calling a professional.

In the case of propane or LP gas, keep in mind that gas is heavier than air, so it accumulates in lower areas first. Before igniting your gas water heater, always inspect and sniff for gas leaks, including the area near the floor. In addition to the above test, use a soapy solution to check all gas fittings and connections.

Before we delve into the troubleshooting tips for gas hot water heaters and discuss common problems and symptoms, let’s familiarize ourselves with how a gas unit functions and its primary components. Once you understand these, troubleshooting will become more manageable, and repairs will be quicker and less expensive.

How Does the Gas Water Heater Work?

It’s important to know how a gas water heater works before attempting to repair it because this knowledge can help you identify the root cause of the problem. Understanding how the different components of the gas water heater function, such as the pilot light, thermocouple, gas valve, and burner, can help you diagnose issues more accurately and determine the appropriate repair steps. This, in turn, can save you time and money and prevent further damage to the unit.

  • The cold water from the house plumbing enters the heater tank through the dip tube and fills the tank from the bottom up.
  • The control gas valve keeps the small pilot light on and ignites the gas burner when there is a call from the thermostat – when the temperature in the tank drops below the set temperature. Heating starts immediately.
  • Hot flue gases run through the flue pipe located in the middle of the tank and transfer heat to the surrounding water, making it warmer and finally hot.
  • Hot flue gases tend to rise and, with the help of the venting system, are finally vented out, either naturally or forced by the power vent.
  • Through the openings at the bottom of the unit and draft hood, sufficient air is provided for proper and stable gas combustion.
  • Once the hot water tap is open for the shower or dishes, hot water is drawn from the top of the unit through the hot water outlet, then the plumbing system, and to the opened hot water faucet. Outgoing hot water is then replaced with the incoming cold water.
  • Every time the temperature inside the tank drops below the set temperature on the thermostat, the gas burner kicks in and starts heating water again.

To provide safe, reliable, and long-term heating, gas models are equipped with several safety elements:

  • The temperature and pressure relief valve or TPR prevents extreme pressure and temperature in the tank, helping the excessive air or water get out.
  • The thermocouple is a temperature sensor, designed as the metal tube where one end is enclosed in the pilot flame. When exposed to higher temperatures, it generates and delivers electrical voltage to the gas valve to open and provide gas to the main burner for gas burning. No flame – no gas supply to the burner.
  • The gas control valve is the device from where the gas is delivered to the gas burner. It opens up if the conditions are met. It is also used to control and set the temperature.
  • For the tank and other part protection from corrosion, glass lining on the inside of the tank and sacrificial anode rod are used.

For the proper repair, it will be assumed that the gas unit was installed correctly and was functioning correctly before the problem occurred.

The problems that are described below are related exclusively to the tank-type models. If you would like to know how to troubleshoot an electric water heater – check out this article, for tankless problems and solution – see this article, and for issues and repairs that are common for both gas and electric tank-type, use this guide.

Note: Basic knowledge of gas and electrical systems is necessary for proper troubleshooting of gas water heaters.

Problem #1: No Hot Water

If you need to perform gas water heater repair, it is important to check if the gas is supplied to your house and if it is delivered to your unit, as there might be obstructions, shortage, or the main gas valve is simply closed.

If hot water suddenly becomes cold, the water usage might have been exceeding the tank capacity. If that is the case, wait for the water heater to recover.

Another problem related to no hot water issue is that the pilot light has gone out. Relight your pilot flame according to the instructions printed on the unit, or find the details here. If the pilot doesn’t relight, you might need a new thermocouple – use this article to learn how to install it and what can go wrong with the thermocouple.

If the device doesn’t perform as it used to do, hot water is actually lukewarm; there might be a lot of sediment build-up, which interrupts the heat transfer.

Did you check if the gas valve is working?

Problem #2: Lack of Oxygen

For the proper operation of gas water heaters, fresh air needs to be delivered for complete gas combustion. The air should enter the gas chamber from the base of the unit and enter the flue vent from below the draft hood.

If there is insufficient air flow, problem symptoms are seen as follows:

The solution is prevention; check and provide enough airflow; check the flue vent and base of the water heater for possible obstructions, and do not cover it with the insulation blanket. Clean the flame arrestor regularly.

Problem #3: Sooting

To effectively repair a gas water heater that is experiencing sooting issues, it’s important to check for potential airflow problems if the device is running and the gas chamber and flue vents are sooted, even if the burner appears to be clean.

If all of these components are sooted, then it may be due to a wrong orifice being used, excessive gas pressure, or loose gas connections in the burner assembly.

If the pilot flame or the main burner flames are too large or small, there might be some dirt and debris in the orifice or gas supply tubing, or an incorrect orifice size has been used. Follow the manufacturer’s manual for the right specs.

Problem #4: Condensation

During the gas water heater’s heating operation, the flue gases can cool to the “dew point,” resulting in condensation, which can now go back to the gas chamber and affect the flame.

Several factors can cause flue gases to cool, including a cold air supply and a cool flue pipe surface. This issue typically occurs when a new heater is filled with cold water for the first time or when a large amount of hot water is used in a short time, and the incoming water is very cold.

Condensation can also occur when combustion efficiency is increased, with more than 87.5% of the flue heat being transferred to the surrounding water.

Symptoms of condensation include water around the heater immediately after the gas water heater operation, water dripping, small black and red spots on the gas burner, water at the top of the heater, and vent piping (which is why PVC or more expensive stainless steel vent pipes are used).

If condensate falls onto the burner, you may hear a sizzling or frying noise, and a large amount of condensate can even extinguish the fire.

To solve this problem, it’s essential to raise the supply air temperature, stored water temperature, or even the tank size (if the existing one is too old and low-performing).

Problem #5: Burner Won’t Stay Lit

The gas burner won’t stay lit due to the following reasons:

  • High ambient room temperature
  • Dirty or clogged air intake
  • Obstructions in the vent
  • Flame arrestor openings are blocked

This article will guide you on how to repair a gas water heater with a gas burner that is not working.

Problem #6: Pilot Light Won’t Light or Stay Lit

The gas water heater repair guide requires you to check if there is any gas at all or if the gas pressure is low. If there is an issue with the gas supply, it is recommended to call the utility company for assistance.

It’s important to bleed the gas line if there is any air trapped, but it should be done by a certified technician).

When attempting to light the pilot, be sure that the pilot light button is fully depressed. Check if the pilot electrode is sparking to the pilot and if the piezo igniter is working properly.

There might also be a defective magnet combined with the thermostat-gas valve, so replace it if necessary.

If the pilot tube or orifice is clogged, clean it. If the thermocouple connection is loose with the gas valve or in the pilot light assembly bracket, tighten it with your finger and 1/4 turn with the wrench; it might need just a simple adjustment.

The thermocouple has to be appropriately secured and in contact with the pilot flame. If it is broken, replace it. If you have melted insulation on the igniter wire or shorting of igniter wire, replace it.

If the pilot light goes out periodically, the following might be the reasons: condensation may be extinguishing the pilot light, insufficient combustion air supply, clogged or incorrect vent system, or inconsistent gas supply and pressure.

If a water heater is equipped with a Honeywell gas valve and there is a problem, it can display green light flashing. Find more about the error codes and how to troubleshoot if you see one or more blinking lights.

Problem #7: Corrosion

Professional gas water heater repair can be necessary if the unit is exposed to contaminated atmospheres in residential or commercial applications, which can cause corrosion.

This often happens when the gas unit is installed near an air supply that contains chemicals and corrosive elements such as chlorine, fluorine, industrial glue, acids, sodium, calcium chloride, cleaning solvents, aerosol with Freon, etc. The air might be ok to breathe, but when exposed to high flame or hot air temperatures, corrosive elements are released, affecting the proper operation.

Common problems include tank and vent corrosion, flue tube collapsing, and heavy scaling on the elements.

The solution to this problem is to avoid installing a water heater near beauty shops and areas exposed to swimming pool chemicals, bleaches, gasoline, etc. If you cannot isolate the unit from the corrosive atmosphere, try to bring the uncontaminated air in for proper combustion.

Avoid Problems by Checking the Vent System

The venting system is significant for safe water heater operation and its efficiency and performance. A vent with a 90-degree elbow installed on the top of the tank draft hood can reduce the vent efficiency by up to 50%.

The recommendation is to install the venting system that rises straight up. For horizontal vent pipes, different installation rules are available (use the manufacturer’s manual for info).

Decompression is another reason why the pilot flame will fail. If air cannot enter as fast as it is being used, the air pressure drops below the outside pressure, creating an effect called “capping.”

The solution for decompression is to make two air vents on the outside wall, one close to the ceiling and the other closed to the ground. If the room is on the balcony, for example, provide a venting opening on the door. Check out how properly to vent a gas water heater.

And, remember, the gas can explode.

Before troubleshooting and repairing a gas water heater make sure that the gas supply is off and always refer to the user manual.


Gas water heaters are an excellent solution for meeting hot water demands in both residential and commercial settings.

However, they can experience a range of issues that affect their performance, safety, and overall functionality, requiring gas water heater repair.

This guide has discussed several common problems that gas water heaters can experience, emphasizing the importance of prompt troubleshooting and repair.

Seeking professional help for complicated repairs or installations is always recommended. Regular maintenance and adherence to manufacturer guidelines can also prevent many issues from arising and extend the life of the gas water heater while ensuring its safe and efficient operation.

Remember, keeping your gas water heater in good condition is not only essential for your comfort but also for your safety. By staying vigilant, addressing issues quickly, and seeking professional help when necessary, you can enjoy the benefits of a reliable and efficient gas water heater for years to come.


Who Repairs Gas Water Heaters?

Gas water heaters can be repaired by licensed and experienced professionals, such as HVAC technicians, plumbers, and gas fitters. It is important to hire someone with the appropriate qualifications and expertise to ensure the safety and proper functioning of the gas water heater. Additionally, many manufacturers have authorized repair service centers or technicians who specialize in their products.

Can I Repair a Gas Water Heater on My Own?

While some minor gas water heater repairs can be done on your own with the right tools and knowledge, it is generally not recommended for safety reasons. Gas water heaters can be dangerous to work on without proper training and expertise. It is important to follow manufacturer guidelines, turn off the gas supply, and refer to the user manual before attempting any repairs. For more complicated repairs or installations, it is recommended to seek the help of a professional.

Is a Gas Water Heater Dangerous?

Gas water heaters can be dangerous if they are not installed, maintained, and used properly. This is because gas water heaters use natural gas or propane as fuel, which can be highly flammable and can cause an explosion if not handled correctly. Gas leaks can also occur if the gas line or connections are damaged or improperly installed, which can lead to carbon monoxide poisoning and other health hazards. Additionally, a faulty gas water heater can lead to fire, scalding, and other safety hazards. To prevent these dangers, it is important to have gas water heaters installed, serviced and  repaired by a qualified professional and to follow manufacturer guidelines for safe use and maintenance.

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