How to Repair a Gas Water Heater: Keeping Your Hot Water Flowing

Having a steady stream of hot water is a modern convenience we often take for granted. But when your hot water heater decides to take a vacation, it can leave you scrambling for cold showers and a way to get your hot water back. Luckily, many common gas water heater problems can be tackled with a little know-how and the right tools.

This Fix-It Guide will walk you through how to repair a gas water heater, including how it works, what can go wrong, and step-by-step instructions for common fixes.

An Overview of How Your Gas Water Heater Works

A gas water heater uses a burner powered by natural gas or propane to heat water stored in a tank. As the water temperature drops below the set point, a thermostat opens a valve that allows gas to flow to the burner.

A pilot light ignites the gas, and the resulting hot gases heat the water in the tank. Once the water reaches the desired temperature, the thermostat closes the gas valve, turning off the burner. Hot water is then distributed throughout your home through pipes.

Common Gas Water Heater Problems You Might Encounter

There are several reasons why you might encounter problems with your gas water heater. Here are some of the most common issues:

No hot water: This could be caused by a pilot light that’s out or not staying lit, a faulty thermocouple, a malfunctioning thermostat, or a lack of fuel.
Not enough hot water: This could be due to a low temperature setting, a clogged flue, or sediment buildup in the tank.
Water is too hot: This is often caused by a faulty thermostat that needs to be replaced or reset.
Leaks: Leaks can come from the pressure relief valve, the drain valve, or the tank itself. A leak can be a sign of a serious problem and may require professional help.
Noise: A noisy water heater could indicate sediment buildup in the tank.

Figuring Out the Problem: How to Diagnose Your Gas Water Heater

Before you dive into repairs, it’s important to identify the specific problem with your gas water heater. Here are some tips:

No hot water? Check to see if the pilot light is on. If it’s out, try relighting it (see instructions below).
Pilot light won’t stay lit? The culprit could be a dirty pilot orifice, a loose thermocouple connection, or a faulty thermocouple.
Not enough hot water? Check the temperature setting on your water heater. You can also try draining the tank to remove sediment buildup.
Water is too hot? Check the thermostat setting. If it’s not set too high, the thermostat may need to be replaced.
Leaks? Locate the source of the leak. Leaks from the pressure relief valve or drain valve may be repairable, but a tank leak typically means replacing the water heater.
Noise? Drain and flush the tank to remove sediment buildup.

Ensure Your Safety: Essential Precautions Before You Begin

Working with gas appliances requires caution. Here are some safety measures to follow before attempting any repairs on your gas water heater:

Turn off the gas supply valve to your water heater before you begin any repairs.
Do not attempt to repair a gas water heater if you smell gas. If you suspect a gas leak, evacuate the area immediately and call your gas company.
Only use the tools and replacement parts recommended for your specific water heater model.

How to Repair a Gas Water Heater: Step-by-Step Fixes

Now that you’ve identified the problem and taken safety precautions, you can tackle the repair. Here’s how to repair a gas water heater:

Relighting the Pilot Light:

Locate the burner access panel and remove it according to the instructions on the panel.
Turn the gas control knob and temperature control dial to their “Off” settings. Wait at least five minutes to allow any gas to clear.
Light a piece of paper and carefully hold it near the pilot burner.
Turn the gas control knob to “Pilot” and press the reset button (if your model has one) while holding the lit paper near the pilot burner. The pilot light should ignite.
If the pilot light ignites, hold the reset button in for about a minute, then release it. If the pilot light stays lit, turn the gas control knob to “On.” The main burner should light.
If the pilot light won’t stay lit, check that the thermocouple tip is positioned correctly in the pilot flame and tighten the nut holding it in place. Try relighting the pilot light. If it still goes out, you may need to replace the thermocouple.

Cleaning the Pilot Orifice:

Turn off the gas valve to your water heater following the instructions in your owner’s manual. Safety first!
Disconnect the burner assembly lines from the gas control valve and remove the burner assembly itself.
Carefully use a thin wire to probe the pilot light orifice. Important: Don’t use a needle or paperclip, as these can damage the delicate orifice.
Vacuum out any dislodged debris that might be blocking the gas flow.

Servicing the Thermocouple:

Locate the thermocouple near the pilot flame. It’s a small metal tube with a wire running from it to the gas control valve.
Check for loose connections where the thermocouple connects to the control valve. Tighten any loose nuts carefully, but avoid over-tightening.
Visually inspect the thermocouple tip. Make sure it’s positioned correctly in the pilot flame for proper heating. You may need to carefully adjust it for optimal contact.

Replacing the Thermocouple:

Turn off the gas control knob and close the gas shutoff valve completely.
Using a wrench, loosen the nut that secures the thermocouple lead to the control unit, then unscrew it by hand.
Remove the old thermocouple from the control unit.
Take your old thermocouple with you when purchasing a replacement to ensure compatibility.
Push the tip of the new thermocouple into the pilot bracket clip as far as it will go and tighten the fitting securely.
Screw the nut at the end of the lead back onto the control unit.
Open the gas shutoff valve and attempt to relight the pilot light following the steps mentioned earlier. If the pilot light won’t stay lit after replacing the thermocouple, it’s best to call a professional for further diagnosis.

Testing and Replacing the Pressure Relief Valve:

Caution: The relief valve releases hot water. Use caution while working on this component.

Make sure the water heater is cool before proceeding. Turn off the hot water system and allow it to cool down completely.
Locate the pressure relief valve on the water heater tank. It typically has a lever arm.
Lift the lever arm on the valve for a few seconds to clear any mineral buildup that might be preventing it from functioning correctly.
If no water spurts out, or if water continues to drip after releasing the lever, the valve needs to be replaced.

Replacing the Pressure Relief Valve:

Turn off the gas control knob and close the gas shutoff valve.
Close the cold-water supply valve to the water heater.
Drain a gallon or more of water from the tank using the drain valve (instructions for draining the tank are covered later in this guide).
Unscrew and remove the discharge pipe (if your model has one) connected to the relief valve.
Use a pipe wrench to unscrew the relief valve from the tank.
Wrap pipe tape around the threads of the new valve to ensure a proper seal.
Screw the new relief valve into the tank by hand, then tighten it securely with a pipe wrench.
Reattach the discharge pipe (if applicable) to the new valve’s outlet.
Refill the water heater and relight the pilot light. If the valve leaks after these steps, consult a plumber to check for high water pressure in your house.

That’s the complete step-by-step guide on how to repair a gas water heater. Following these steps and using caution, you can potentially save yourself the cost of a plumber’s visit. However, for more complex repairs or if you’re uncomfortable with any of the steps, it’s always best to call a qualified professional. Speaking of professional plumbers, you can trust JMK Plumbing. With years of experience, JMK plumbing has resolved thousands of plumbing queries for Miami residents.

How to Replace the Drain Valve in a Gas Water Heater?

Replacing the Drain Valve:

A faulty drain valve can lead to leaks and hinder your ability to flush sediment buildup from the tank. Here’s how to replace it:

Safety First: Turn off the gas control knob and close the gas shutoff valve completely.
Empty the Tank: Close the cold-water supply valve that feeds the water heater. You’ll need to drain the tank completely, which can be done by attaching a garden hose to the drain valve and running it outside to a drain (or sump pump if your heater is in the basement). Open the drain valve and allow the tank to drain entirely.
Unscrew the Old Valve: Once the tank is empty, use a pipe wrench to loosen and remove the base of the drain valve.
Install the New Valve: Purchase a replacement drain valve that’s compatible with your specific water heater model. Wrap pipe tape around the threaded end of the new valve to create a watertight seal. Carefully screw the valve into the coupling that connects to the tank.
Attach Pipes: Apply pipe tape to the pipe threads where they emerge from the water heater tank. Screw the coupling and the new valve together onto the nipple, then tighten securely. Ensure the valve is facing downward for proper drainage.
Refill and Relight: Reopen the cold-water supply valve and allow the tank to refill completely. Once full, close any nearby hot water faucets to prevent air from entering the system. Then, relight the pilot light following the instructions in the earlier section.

How to Test and Maintain the Flue and Vent in a Gas Water Heater?

A properly functioning flue and vent are essential for safely venting combustion gases from your water heater. Here’s how to test and maintain them:

Test the Draft:

Set your water heater to a high temperature to ignite the burner and let it run for at least 10 minutes. Carefully hold a lighted match near the edge of the draft hood. If the vent is functioning correctly, the flame on the match should be drawn inward slightly.

You can also briefly blow out the match – if the smoke is sucked up into the hood, that’s another good sign. Conversely, if the flame or smoke is blown away from the hood, it indicates a potential blockage in the vent system.

Clear Blockages (if needed):

Before attempting any disassembly, turn off the water heater completely, close the gas shutoff valve, and allow the burner, draft hood, and vent to cool completely.

Safety is crucial! Once cool, you can remove the burner access panels for better access. Cover the burner and floor area with paper to catch soot and debris during cleaning.

Remember: Always refer to your owner’s manual for specific disassembly instructions for your water heater model.

Disassemble and Clean:

Mark the vent sections for proper reassembly during the cleaning process. Detach the draft hood from the top of the tank and clean it thoroughly with a wire brush.

Look for any rusted or damaged ductwork that might need replacing. With the vent removed, carefully lift out the baffle (a plate that helps direct heat flow) from the flue and use a wire brush to remove soot buildup.

Reassemble and Relight:

After cleaning the vent components, reinstall the baffle, draft hood, and vent sections according to the markings you made earlier. Use a vacuum cleaner to remove any soot or debris from inside the combustion chamber.

Clean the burner and its ports with a small brush to ensure proper gas flow.

Finally, relight the pilot light and retest the draft using the match test described earlier. If the flame or smoke isn’t drawn upward after cleaning, there might be a blockage in the main chimney. In this case, it’s best to call a professional for further inspection and service.

How to Drain a Gas Water Heater?

Draining the Gas Water Heater Tank:

Regularly draining your water heater tank helps remove sediment buildup that can reduce efficiency and water heater lifespan. Here’s how to do it safely:

Turn off the Gas and Water Supply: As always, safety is paramount. Turn off the gas control knob to your water heater and close the gas shutoff valve. Additionally, shut off the cold-water supply valve that feeds the heater.

Open a Hot Water Faucet: Open a hot water faucet somewhere in your house (like in the kitchen sink) to help speed up the draining process.

Attach and Drain: Connect a garden hose to the drain valve and run the hose outside to a drain (or sump pump if your water heater is located in the basement). Make sure the hose is long enough and positioned so that the water will drain completely.

Drain the Tank: Open the drain valve completely and allow all the water to drain from the tank. This may take some time depending on the size of your water heater.

Close the Valve and Refill: Once the tank is empty, close the drain valve securely. Reopen the cold-water supply valve and allow the tank to refill completely. You’ll know the tank is full when a steady stream of water flows from the hot water faucet you opened earlier. Close the hot water faucet once the tank is refilled.

Relight the Pilot Light: With the tank refilled, you can now relight the pilot light following the instructions outlined in the earlier section of this guide.

Note: After draining and refilling your water heater, you may need to bleed any air trapped in the pipes. Open a hot water faucet closest to the water heater and let it run until a steady stream of hot water flows, indicating all the air has been purged from the system.

Final Words

So these are the step-by-step instructions on how to repair a gas water heater. When implemented right, you can address some common gas water heater repairs and maintenance tasks yourself. However, it’s important to be realistic about your DIY skills and comfort level.

If you’re unsure about any step or suspect a more complex problem, don’t hesitate to call a qualified plumbing company such as JMK plumbing to ensure your water heater is repaired safely and efficiently.