Introduction
Gas water heaters are reliable, energy-efficient systems that provide consistent hot water for years. But like any appliance, they can experience problems over time. Among the many issues homeowners face, one stands out as the most common—and the easiest to recognize: a pilot light that won’t stay lit or a failing thermocouple.
At Fayetteville Plumbing Services, we diagnose and repair water heater issues every day. Here’s a closer look at why this problem happens, how it affects your hot water supply, and what you can do about it.
Understanding How a Gas Water Heater Works
To understand why the pilot light or thermocouple causes most gas water heater issues, it helps to know how the system functions.
A gas water heater has a burner assembly at the bottom of the tank. The pilot light ignites the burner whenever the thermostat senses that the water temperature has dropped below the set point.
The thermocouple (or flame sensor in newer models) detects whether the pilot light is burning. If it doesn’t sense a flame, it shuts off the gas supply to prevent dangerous leaks.
If either of these components fails, the burner won’t ignite—and you’ll be left with cold water.
The Most Common Problem: Pilot Light or Thermocouple Failure
The number one reason homeowners lose hot water in a gas system is that the pilot light goes out or the thermocouple malfunctions.
Pilot Light Issues
If the pilot light won’t stay lit, possible causes include:
- Dirty pilot orifice: Dust, soot, or debris can block the small flame.
- Weak gas flow: A partially closed gas valve or low gas pressure can extinguish the flame.
- Drafts or air movement: Nearby ventilation or open doors can blow out the flame.
- Faulty thermocouple: The thermocouple may not sense the flame correctly and shut off gas flow prematurely.
Thermocouple Issues
The thermocouple is a small copper wire that sits near the pilot flame. Over time, it can:
- Become coated with carbon or corrosion
- Bend out of position
- Wear out from heat exposure
When that happens, it fails to send the correct signal to keep the gas valve open, and the pilot goes out repeatedly.
Other Common Gas Water Heater Problems
While the pilot and thermocouple are the most frequent culprits, several other issues can affect performance:
a. Faulty Gas Control Valve
If the gas control valve fails, gas won’t reach the burner. You might hear clicking or smell gas, but the water heater won’t ignite.
b. Sediment Buildup
Over time, minerals from hard water settle at the bottom of the tank. This buildup insulates the burner from the water, making heating less efficient and causing popping or rumbling noises.
c. Clogged Vent or Flue
A blocked flue restricts proper combustion airflow. This can cause backdrafting, soot buildup, and incomplete heating.
d. Thermostat Malfunction
If the thermostat fails, it may not signal the burner to fire up, even when the water is cold.
How to Troubleshoot a Gas Water Heater with No Hot Water
Before calling a plumber, try these basic steps:
- Check the pilot light. If it’s out, follow the manufacturer’s instructions to relight it safely. Most gas heaters have a small window near the base for viewing the flame.
- Inspect the gas supply. Ensure the gas valve is open and other gas appliances (like your stove) are working.
- Look for drafts. Eliminate airflow near the pilot area that could blow out the flame.
- Reset the thermostat. Turn the control knob to “pilot,” relight, and set it back to “on.”
If the pilot won’t stay lit after several attempts, the thermocouple may need cleaning or replacement.
When to Call a Professional Plumber
Gas systems involve both flammable gas and open flame, so safety is critical. If you smell gas, hear hissing, or notice the flame won’t stay lit even after resetting, turn off the gas supply and call a professional immediately.
At Fayetteville Plumbing Services, our licensed plumbers can:
- Test your thermocouple and gas valve
- Clean or replace the pilot assembly
- Inspect the burner, flue, and thermostat
- Check for carbon monoxide leaks or ventilation issues
We also ensure your system meets safety codes and operates efficiently, giving you reliable hot water and peace of mind.
Preventing Gas Water Heater Problems
Routine maintenance is the best defense against recurring issues. To keep your gas water heater running efficiently:
- Schedule annual inspections to test the thermocouple and clean the burner assembly.
- Flush the tank yearly to remove sediment and prevent corrosion.
- Keep the area around your water heater clean and free of dust or debris.
- Check the pilot flame color—it should burn blue with a small yellow tip. A mostly yellow flame may indicate incomplete combustion.
Regular professional maintenance extends your water heater’s life and helps avoid costly repairs.
When to Replace Instead of Repair
If your gas water heater is more than 10–12 years old, constant pilot or thermocouple issues may be a sign it’s time for replacement. Newer models are more energy-efficient and include modern safety sensors and electronic ignition systems that eliminate the need for a standing pilot flame.
At Fayetteville Plumbing Services, we’ll help you determine whether repair or replacement is the better investment and recommend the best options for your home’s needs and budget.
Conclusion
The most common problem with gas hot water heaters is a pilot light or thermocouple failure, which prevents the burner from igniting. While relighting the pilot is simple, repeated outages or flame issues usually require professional repair.
If your water heater won’t stay lit, makes unusual noises, or struggles to maintain hot water, call Fayetteville Plumbing Services. Our experienced team provides prompt diagnostics, expert repair, and honest recommendations to restore your home’s hot water fast.
