Pool Heating

Pool Heater Not Working: Step-by-Step Fix Guide

When your swimming pool heater stops working, the problem is often a simple flow issue or a tripped breaker. This guide walks you through the diagnostic steps to restore warmth to your water without calling a professional.

Pool Heater Not Working: Step-by-Step Fix Guide

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FibroPool FH135 35,000 BTU Electric Pool Heat Pump - 120V Above Ground & Inground Pool Heater up to 7,500 Gal, High Efficiency COP 5.55, No

  • 35,000 BTU HEATING POWER: This 35k BTU pool heater delivers steady warmth for small pools and spas. Ideal as an above ground pool heater or compact inground pool heater to extend your swim season.
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Common Reasons Your Pool Heater Stopped Working

Finding that your pool heater is not working can be frustrating, especially when you are ready for a swim. Before you assume the worst, remember that most issues stem from basic maintenance gaps or power supply interruptions. The most frequent culprits include low water flow, tripped circuit breakers, dirty filters, or thermostat settings that have been inadvertently changed.

If you find your Pentair pool heater not turning on, or if you are struggling with a Hayward pool heater not turning on, do not panic. Many of these machines share similar internal components that respond well to standard troubleshooting. Whether you have a gas unit or an electric heat pump, checking the basics first will save you from an unnecessary service call fee, which typically ranges from 150 to 300 dollars.

Step 1: Check the Water Flow and Filters

The most common reason for a swimming pool heater not working is a lack of sufficient water flow. Heaters have built-in safety switches that prevent the heating element or burner from igniting if the water is not circulating properly. If your pump is struggling, it cannot push enough water through the heater to trigger the sensor.

First, check your pool pump. If the pump is not moving water, the heater will remain off. If you suspect a problem, refer to our guide on Pool Pump Not Priming to restore circulation. Additionally, check your filter pressure. A dirty filter restricts flow. Backwashing your sand filter or cleaning your cartridge filter can often resolve the issue immediately. Cost for filter maintenance is generally just the price of cleaning supplies, usually around 20 to 40 dollars.

Step 2: Inspect Power Supply and Breakers

If the water is flowing but the pool heater won't turn on, look at the electricity. A tripped circuit breaker is a frequent cause for a pool heater not turning on. Check your main electrical panel for any switches that have moved to the middle position or the off position. Reset the breaker by flipping it all the way to off and then back to on. If you notice the breaker tripping repeatedly, it is a sign of an internal short or a motor overload, which requires a professional inspection to prevent fire hazards.

If you are looking for a reliable, easy-to-install solution for smaller pools, consider the Electric Pool Heater, 30,000 BTU Pool Heat Pump for Above Ground Pools Up to 7000 Gallons. This unit is a top pick because it features a 120V plug and play design. Because it operates on standard household power, you avoid the high costs of professional electrical upgrades. It is highly efficient and perfect for pools up to 7,000 gallons.

Step 3: Thermostat and Sensor Calibration

Sometimes, the pool heater is working, but it thinks the water is already at the target temperature. Verify your thermostat settings. If the set temperature is lower than the current water temperature, the heater will not engage. It sounds simple, but a family member may have changed the setting.

If the settings are correct, the temperature sensor might be faulty. Sensors can degrade over time, sending incorrect data to the control board. Replacing a temperature sensor is a moderate DIY task that costs approximately 50 to 100 dollars for the part. If your unit is older, this is a common point of failure.

Step 4: Gas Heater Specific Troubleshooting

If you have a gas or propane pool heater, the ignition system is often the source of the problem. If the heater makes a clicking sound but fails to light, you may have a blocked gas line, a faulty igniter, or an issue with the flame sensor. Ensure your gas valve is in the open position and that your propane tank has sufficient fuel.

For those dealing with a persistent failure to ignite, cleaning the burner tray or replacing the hot surface igniter can be effective. An igniter replacement usually costs between 80 and 150 dollars. If you smell gas, shut off the gas supply immediately and call a professional. Never attempt to repair gas lines or internal gas valves unless you are a licensed professional.

Step 5: Evaluating Heat Pump Efficiency

If you have an electric heat pump, it relies on ambient air temperature. If the outside temperature is too low, the heat pump may not be able to extract enough heat from the air to warm the pool effectively. This is why many people prefer the FibroPool FH135 35,000 BTU Electric Pool Heat Pump. This unit is designed for high efficiency with a COP of 5.55, meaning it produces more heat while using less electricity. It works well for pools up to 7,500 gallons and is a great upgrade if your old unit is simply too expensive to run.

Another high-performance option is the Swimming Pool Heat Pump, Electric Swimming Pool Heater for Above Ground Pools. With 45,000 BTU output, it provides faster heating for those living in cooler climates. Investing in a quality heat pump can often be more economical in the long run than repeatedly repairing an aging, inefficient gas heater.

When to Call a Professional

While many maintenance tasks are easy for homeowners, some situations require an expert. If you have replaced the sensor, checked the flow, and reset the breakers, but the pool heater still refuses to start, there may be a deeper issue with the control board or the heat exchanger. These parts are expensive, often costing 400 to 800 dollars, and their installation requires specialized knowledge.

Additionally, always call a pro if you notice:

  • Water leaking inside the heater cabinet.
  • Evidence of burnt wiring or a strong odor of melting plastic.
  • Gas leaks or a persistent smell of sulfur.
  • The heater makes loud grinding or banging noises during operation.

A professional technician will have the diagnostic tools to test the circuit board voltage and pressure switches safely. Hiring a pro is safer than experimenting with high-voltage electrical components. Most professional repairs, including labor, will run between 300 and 600 dollars, depending on the complexity of the repair and the cost of the replacement parts.

Preventative Maintenance Tips

To avoid needing these repairs in the future, keep your water chemistry balanced. High acidity can corrode the heat exchanger, leading to leaks that are not cost effective to repair. Use our guide on How to Lower Pool pH to ensure your water remains non-corrosive. Additionally, keep the area around your heater clear of leaves and debris. Proper airflow is essential for both gas heaters and electric heat pumps to function efficiently. If you have a hot tub, be sure to also check for issues using our Hot Tub Not Heating troubleshooting guide to keep your spa in top shape. A simple check every month can extend the life of your equipment by several years.

By following these diagnostic steps, you can save hundreds of dollars in service fees. Start with the easiest solutions like cleaning your filters and checking your power supply. Only when you have exhausted these options should you consider calling a professional to handle complex internal repairs. With a little patience, you will have your pool back to the perfect temperature in no time.

Our Recommendation
🏆 TOP PICK

Electric Pool Heater, 30,000 BTU Pool Heat Pump for Above Ground Pools Up to 7000 Gallons, WiFi Control, 120V Titanium Heat Exchanger, V7 Pl

  • Perfect Pool Heat Pump for Small Pools up to 7,000 Gallons: Designed for above ground pools and small backyard pools, this 30,000 BTU pool heat pump delivers efficient, consistent heating without overspending on oversize
  • 120V Plug & Play Pool Heater - No Professional Installation Needed: Skip the complicated wiring. This 120V electric pool heater runs on standard household power, making setup fast and easy. Simply connect to your existin
  • Energy-Efficient Heating to Reduce Electricity Costs: Save on energy bills compared to traditional electric pool heaters. This energy-efficient pool heat pump uses advanced heat exchange technology to deliver more heat w
  • Smart WiFi Control with Heating & Cooling Modes: Enjoy full control of your pool temperature anytime, anywhere. This WiFi pool heater allows you to adjust temperature, set schedules, and automate operation through your p
  • Durable Titanium Heat Exchanger for Saltwater & long term Use: Built for durability and reliability, this pool heat pump features a titanium heat exchanger, making it ideal for saltwater pools and resistant to corrosion.
Check Price on Amazon

FibroPool FH135 35,000 BTU Electric Pool Heat Pump - 120V Above Ground & Inground Pool Heater up to 7,500 Gal, High Efficiency COP 5.55, No

  • 35,000 BTU HEATING POWER: This 35k BTU pool heater delivers steady warmth for small pools and spas. Ideal as an above ground pool heater or compact inground pool heater to extend your swim season.
  • ENERGY EFFICIENT HEAT PUMP: Advanced heat pump pool heater technology transfers heat from the air for up to 5.5x efficiency. A smart electric pool heater option for consistent water temperature control.
  • FULLY ELECTRIC 120 V: Operates on 120 V household power with no gas or propane required. This electric above ground pool heater simplifies installation and helps reduce ongoing fuel handling.
  • VERSATILE POOL COMPATIBILITY: Designed for above ground and inground installations, this swimming pool heat pump supports pools, spas, and hot tubs as a reliable pool pump heater solution.
  • COMPACT AND QUIET DESIGN: Space saving round cabinet fits tight equipment pads. The streamlined pool heat pump system features low noise operation and minimal moving parts for easy upkeep.
Check Price on Amazon

Swimming Pool Heat Pump, Electric Swimming Pool Heater for Above Ground Pools, up to 5000gallons, Max Output 45000BTU/hr, Heat Exchanger,240

  • 1.316# stainless steel, Best in its class
  • 2.45,000 Btu/Hr heating capacity, 11KW
  • 3.Suitable for pools up to 5000 gallons in coastal climates
  • 4.Suitable for ALL Hot Tubs,Above Ground Inground Pool Swimming Pool.
  • 5.240 Volts 50A - 60 HZ American Voltage.Use With Water Pump.
Check Price on Amazon

Frequently Asked Questions

Why is my pool heater not turning on?

The most common reasons are low water flow due to a dirty filter, a tripped circuit breaker, or an incorrect thermostat setting.

How much does it cost to fix a pool heater?

Simple DIY fixes usually cost under 100 dollars for parts, while professional repairs typically range from 300 to 600 dollars depending on the part failure.

Can I replace a pool heater part myself?

Yes, many parts like temperature sensors, igniters, and filters are manageable for DIYers, but you should call a professional for gas line or high-voltage electrical work.

Disclaimer: This article is for informational and educational purposes only. It does not constitute professional advice. Always consult a qualified professional before making decisions based on this content.
Chris W.

The Pool Spa Fix editorial team publishes expert-reviewed content on Pool and hot tub troubleshooting, repair guides, and equipment reviews.