If you’re struggling with a pool heater that won’t stay lit, you’re not alone. This issue is one of the most common heating system complaints made by pool owners across the country. Whether you heat a small backyard pool or a commercial swimming facility, a consistently lit pilot is essential for maintaining a comfortable water temperature. In this in-depth guide, we’ll explore what causes a pilot to go out—and how it can be diagnosed and fixed efficiently.
Understanding Pool Heaters and the Pilot’s Role
Before diving into troubleshooting, it’s important to understand how a pool heater works, particularly the role that the pilot light plays in the system. Most traditional pool heaters are gas-fired—running on either propane or natural gas. These heaters typically feature a pilot light or an electronic ignition system that ignites the burner. The pilot stays lit continuously, ready to flare the burners into full operation whenever the thermostat demands heat.
Pilot Light vs. Electronic Ignition Systems
Not every pool heater uses a continuous pilot system. Some modern heaters feature an intermittent pilot ignition (IPI) or hot surface ignition system. These use an electric spark to light the pilot briefly only when the heater is activated. While this is more energy efficient, it also introduces new mechanical components that must be diagnosed if the heater won’t remain lit.
Regardless of the system type, if your pool heater doesn’t hold a flame, this means something is preventing the pilot or the main burner from staying lit beyond the initial ignition attempt.
Common Causes of Pilot Light Failure
There are several reasons a pilot light may fail to stay lit. Let’s explore the most common ones:
1. A Faulty Thermocouple
The thermocouple is a safety device designed to shut off the gas flow if the pilot flame goes out. If it’s not working properly—or not sensing the flame as it should—it’ll shut off gas before the system can continue running.
Signs of a faulty thermocouple:
- Pilot lights but immediately goes out after releasing the ignition button.
- Thermocouple appears rusted, corroded, or physically damaged.
2. Improper Pilot Positioning or Flame Contact
The thermocouple needs to be exposed to the pilot flame in order to conduct the needed voltage to keep the gas valve open. If the flame no longer touches the thermocouple—due to misalignment, venturi obstruction, or debris accumulation—the signal is lost.
3. Gas Supply Interruptions
If the pool heater cannot receive a steady gas supply, the pilot will either not light or stay lit only briefly. This can be caused by:
- Low gas pressure due to regulator issues.
- Gas valves that are partially closed.
- Leaks or blockages in the gas lines.
4. Airflow or Draft Issues
Excessive drafts, poor venting, or foreign obstructions can all blow out a pilot flame or interfere with proper combustion. Wind, nearby electric fans, or poor installation in breezy environments can introduce unwanted airflow near the pilot chamber.
5. Electrical and Ignition System Failures
In heaters using ignition modules or IPI systems, problems can point to the control board, spark igniter, or safety sensors. These are usually more complex than simple thermocouple issues and sometimes require professional diagnostics.
Step-by-Step Troubleshooting Guide
Follow this step-by-step guide whether you’re doing the job yourself or handing it to a technician.
Step 1: Check the Basics
Reignite the Pilot
The first test is to relight the pilot and observe what happens. Use the heater manufacturer’s manual for the correct steps, as the ignition method varies by brand and heater model. If the pilot lights but won’t stay on, don’t proceed to the burners—start checking potential faults.
Confirm Gas Availability
Make sure that:
- The gas supply valve is fully open
- There’s no smell of gas (indicating a potential leak)
- The heater is correctly plumbed into the home or facility’s gas line
Step 2: Inspect the Thermocouple
If the pilot will not stay lit, check the thermocouple:
- Is it in contact with the pilot flame?
- Is there soot, corrosion, or bending that might interfere with heat detection?
- Is it producing a sufficient millivolt signal?
You can test the thermocouple using a millivolt meter, which should read at least 25 millivolts when the pilot is lit and the button is being held down.
Step 3: Check the Gas Valve and Pilot Tube
The pilot tube, which carries gas to the pilot light, can become clogged with dust or spider nests. Turn off the gas and disassemble the pilot tubing to blow it out and remove debris. Similarly, the gas valve could be partially closed or restricted—inspect all control valves for blockages or wear.
Step 4: Ensure Proper Drafting / Ventilation
The combustion chamber, exhaust, and air intake of the pool heater must remain clear of debris, leaves, or spider webs. Improper venting could starve the heater of oxygen or pull in winds that extinguish delicate pilot flames.
Step 5: Investigate Electronic Components
For heaters using time-delay ignition or IPI systems, the control module or spark igniter can malfunction. Diagnosing these requires testing the wiring connections or using a meter to check module operation.
Prevention and Ongoing Maintenance Tips
The best solution to a problematic pilot is often prevention—routine maintenance keeps the system clean, functional, and reliable year after year.
1. Clean the Pilot Assembly Twice a Year
Especially before heating season and after long off-season storage, taking time to clean the pilot tube and verify thermocouple contact can prevent relighting issues.
2. Monitor for Rust and Corrosion
Outdoor pool heaters face weather extremes. Corrosion or rust on the thermocouple or electrical components can cause intermittent problems. Replace corroded parts as needed.
3. Check Gas Line Pressure Annually
Use a manometer or call a technician to test your propane or natural gas system pressure. Low pressure can result in weak pilot flames or unstable ignition.
4. Schedule a Pre-Season Professional Tune-Up
Annual inspection by a certified technician can catch small issues before they lead to complete heater failure. They’ll evaluate:
- Heat exchanger condition
- Gas valve performance
- Flame sensing operations
- Electrical systems for wear
Repair or Replace – When to Upgrade Your Pool Heater
Sometimes, the pilot light issues stem from age or a heater system that is no longer worth the investment of repairs. Here’s when to consider upgrading:
Is the Heater Over 10–15 Years Old?
Most pool heaters have a service life between 8 and 15 years. If your heater is older and has frequent failures—pilot related or not—it’s often more cost-effective to install a new, more efficient model.
Is Efficiency a Concern?
Modern high-efficiency pool heaters include:
- Electronic ignition systems
- Stainless steel heat exchangers
- Modulating burners for better temperature control
If energy efficiency matters, replacing a constantly failing heater may lower your long-term costs.
Are Repairs Becoming Too Costly?
If the cost of fixing thermocouples, ignition modules, and pilot lines starts adding up, it’s financially better to invest in a new heater. Especially in commercial settings, downtime and maintenance costs heavily affect the cost-benefit equation.
When to Call a Professional Technician
While some pilot light issues can be cleared with DIY efforts, not all problems are safe or simple to fix independently. Consider contacting a licensed HVAC or pool equipment technician if:
- The pilot won’t stay lit despite troubleshooting
- The gas smell is strong at ignition
- There are visible cracks in the heat exchanger
- Burners light unevenly or produce yellow flames (a carbon monoxide risk)
Gas-fired equipment is potentially dangerous if improperly handled. It’s better to be safe than sorry. A qualified technician will also help diagnose subtle control board failures that often lead to non-obvious heater operation errors.
Choosing the Right Replacement Heater
If it’s time to upgrade or replace, use the following criteria to choose a new pool heater:
1. Fuel Type:
- Propane: Higher operating cost but can be used where natural gas isn’t available.
- Natural Gas: Usually cheaper per BTU, ideal where available.
- Electric (Heat Pumps): Efficient but best in moderate climates.
2. BTU Output:
A higher British Thermal Unit (BTU) rating heats water faster but costs more to run. Match the BTU to your pool size for the correct capacity.
3. Efficiency Rating (EF):
Look for the Energy Factor (EF) rating, which tells you how efficiently the heater operates. Higher EF = more efficiency.
4. Ignition System:
Choose between standing pilot ignition or intermittent pilot ignition for best cost-benefit per your usage.
Conclusion: Staying on Top of Pilot Light Problems
“If my pool heater won’t stay lit” is a common concern that reflects deeper operational issues. A pilot that fails to stay lit points to simple problems like thermocouples and minor obstructions—or more significant wear like failing ignition systems. By diagnosing and resolving the issue promptly, pool owners can enjoy uninterrupted service through the swimming season.
Remember to keep maintenance routines consistent, look for signs of wear early, and prioritize equipment safety and longevity. Whether you choose to learn the inner workings of pool heaters for hands-on repair or call a skilled technician, addressing pilot lighting problems can extend the lifespan of your system and provide a consistently warm swimming experience.
If you’re unable to resolve the issue after troubleshooting common causes, consult with a licensed technician who can provide diagnostics and advanced repair services tailored to your heater brand and model.
Why does my pool heater pilot light keep going out?
There are several common reasons why a pool heater pilot light won’t stay lit. One frequent cause is a faulty thermocouple, which is responsible for sensing whether the pilot flame is burning and signaling the gas valve to stay open. If the thermocouple is damaged, improperly positioned, or not functioning correctly, it can cause the pilot to extinguish when the knob is released. Another common issue is a lack of proper gas flow, which might be due to low gas pressure, a closed valve, or a blockage in the gas line, preventing the pilot from staying ignited.
In addition to gas and thermocouple issues, environmental factors like wind or drafts around the heater can also blow out the pilot flame. Furthermore, buildup of dirt or debris in the pilot assembly may obstruct the flame from making proper contact with the thermocouple, which results in the system shutting down. To address this, it’s important to inspect the pilot area for cleanliness and check for any signs of wear or damage to components like the thermocouple or gas valve. If you’re uncertain about the exact cause, consulting a qualified technician is recommended.
How do I relight the pilot light on my pool heater?
Relighting the pilot light on your pool heater typically involves a series of steps to ensure safe and effective ignition. Begin by turning the gas valve to the “off” position and waiting for a few minutes to allow any residual gas to dissipate. Next, turn the knob to the “pilot” setting and use a long match or lighter to ignite the pilot while holding it down. Once the pilot is lit, continue holding the knob for about 30 seconds to allow the thermocouple to heat up before releasing it and turning the knob to the “on” position.
It’s crucial to follow the specific instructions provided by the manufacturer for your particular heater model, as control panel designs and ignition procedures can vary. If the pilot refuses to light or goes out once you release the knob, the issue may be with the thermocouple, gas supply, or another internal component. In such cases, further troubleshooting may be necessary, or you may need to contact a professional technician to assess and resolve the problem safely.
What is a thermocouple and how does it affect the pilot flame?
A thermocouple is a safety device installed in your pool heater that generates a small electrical current when heated by the pilot flame. This current signals the gas valve to remain open, allowing gas to flow and keep the pilot lit. If the thermocouple isn’t properly positioned or doesn’t receive enough heat from the pilot flame, it won’t generate the necessary signal and the gas valve will shut off, causing the pilot to go out. A functioning thermocouple helps prevent unburned gas from accumulating in the system, which is essential for safe operation.
If the thermocouple is old or damaged, it may no longer function correctly and should be replaced. To test its function, light the pilot and hold the knob down for the specified period before releasing. If the flame goes out immediately, the thermocouple is likely the issue. Cleaning, adjusting, or replacing the thermocouple can often resolve pilot-related problems. Always ensure the pilot flame fully engulfs the thermocouple tip to maintain a stable reading and uninterrupted heater performance.
Is a dirty pilot assembly causing my pool heater to fail?
Yes, a dirty pilot assembly is a common cause of a pool heater failing to maintain a pilot flame. Over time, dust, dirt, and spider webs can accumulate in the small openings of the pilot tube or around the burner assembly. This buildup can prevent the proper flow of gas to the pilot, resulting in intermittent or failed ignition. Additionally, if the pilot flame does not reach the thermocouple due to a weak or erratic flame caused by debris, the heater’s gas valve may shut down, extinguishing the pilot.
To resolve this issue, the pilot assembly can often be cleaned using a small wire brush, compressed air, or a needle to clear any blockages in the pilot tube. However, caution should be exercised to avoid damaging delicate components during cleaning. After clearing the debris, the pilot should ignite more easily and remain lit. If cleaning the pilot assembly doesn’t resolve the problem, it may be necessary to inspect other components like the thermocouple or gas pressure system for further signs of malfunction.
Can wind or improper installation affect the pilot flame?
Yes, environmental factors such as wind or inadequate installation of the pool heater can cause the pilot flame to extinguish. If the heater’s venting and combustion air supply are not properly shielded from strong breezes or drafts, wind can blow out the small pilot flame, especially if the heater is located in an area with consistent wind exposure. Improper vent installation or the absence of wind baffles can also disrupt combustion, leading to heater malfunctions or a pilot that won’t stay lit.
Proper installation is essential for consistent pilot operation and overall heater efficiency. A pool heater must be installed according to manufacturer and local code requirements to ensure correct airflow, gas supply, and venting. If wind is a known issue in the heater’s location, installing a wind shield or relocating the unit (if possible) may be necessary. Consult a licensed technician if you suspect installation or wind-related issues are at fault to avoid risking heater performance or safety hazards.
What should I do if my heater has gas but the pilot won’t light?
If your pool heater has a gas supply but the pilot won’t light, start by verifying that the gas control valve is set to the “pilot” position and that you’ve allowed sufficient time for residual gas to clear the lines before igniting. Ensure you’re using a reliable igniter or match and that the pilot gas orifice is not clogged or obstructed. If the gas is on but the pilot does not ignite, the problem may lie with a blockage in the pilot tube or a faulty ignition system, especially if your heater has an electronic igniter instead of a manual pilot.
Additionally, check the thermocouple and pilot assembly for any signs of wear, misalignment, or dirt buildup. An improperly seated thermocouple may prevent the pilot from staying lit even if it ignites initially. If the pilot still won’t light after these inspections, the gas pressure may be too low or the valve may be defective. In this case, contact a professional technician to test gas pressure and perform any necessary repairs or component replacements to bring the heater back into safe and proper working order.
When should I call a professional for pilot light issues?
While many pilot light issues can be resolved through basic troubleshooting and maintenance, some situations require the expertise of a professional technician. If you’ve checked common causes like the thermocouple, gas supply, pilot cleanliness, and ignition system without resolving the issue, it may be time to seek professional help. Issues such as faulty gas valves, internal wiring problems, or low gas pressure often require specialized tools and technical knowledge to diagnose and repair safely.
Moreover, if you smell gas, experience persistent ignition problems, or hear unusual noises from the heater, it’s critical to shut off the system and contact a licensed HVAC technician or pool equipment specialist immediately. These could be signs of serious mechanical issues that could lead to unsafe conditions if not addressed properly. Regular maintenance from a qualified technician can also help prevent recurring pilot light problems and prolong the life of your pool heater.