Pool Heater Troubleshooting: How to Fix Common Issues - Pool Research (2024)

Having a pool heater is a great way to enjoy a warm dip in the pool as the summer months dwindle away. But, if your heater stops working, what should you do? The last thing you want is for your pool to be freezing cold! In my handy guide, I will go over some of the most common ways of troubleshooting a swimming pool heater so that you can get it up and running again.

Main Takeaways

  • When troubleshooting a pool heater, check the power, temperature settings, filter, pool pump, and plumbing valves.
  • Some common issues with gas pool heaters are with the pilot light, leaks, dark exhaust, and rust.
  • I recommend contacting a professional to help with complex fixes such as electrical, plumbing, or motor issues.
  • If you’ve tried troubleshooting your pool heater, but it is still not running correctly, you may need to replace some parts.

How to Troubleshoot Your Pool Heater

If your pool heater is not functioning properly, don’t rush into purchasing a new one. In fact, sometimes, getting your heater running again is a quick and easy fix. Let’s explore some of the most common ways to troubleshoot a pool heater.

Check the Power

The power source is one of the most common culprits when troubleshooting a pool heater. Sometimes, the fix can be as simple as ensuring the pool heater is plugged in properly.

Check to ensure that your pool heater is properly connected to the power source and that there are no electrical connection issues. As you inspect, keep a close eye on damaged wiring and look at the breaker to ensure the pump has enough power to operate.

Examine Error Codes

If you find that your power heater turns on but then keeps shutting off, this could indicate that you are having water pressure issues. Your first step should be to look at any error codes that might be displayed.

If you see error codes, including “Lo/Hi” or “Flo,” this is usually an indication that your pool heater is not getting enough water. Reasons that your pool heater may not be getting enough water include filter issues and pressure issues.

Examine Power Sources

If you do not see an error message and, instead, your pool heater just shuts off immediately after or shortly after turning it on, this can indicate a power issue. In this case, you will want to check your power sources and connections to ensure everything is as it should be. Checking the breaker, resetting the unit, and going over connections are the steps you will want to take.

Check the Temperature Settings

Most pool heaters are incredibly temperamental when it comes to temperature. If your pool heater is not set to a high enough temperature, it may not appear to be working (though it’s working just fine).

Ensure that the pool heater’s thermostat has a higher temperature setting than the current water temperature of your pool. This way, the water being pumped in is actually warmer.

Check Your Outdoor Temperature Settings

With some pool heat pumps, if the outside air temperature is too cold, the heater will not run and keep up the water. There are different types of pool heaters, including gas and electric heaters. In general, gas heaters tend to be more effective at colder temperatures. So, if you live in an especially cold area, I recommend investing in a gas heater.

Some high-quality electric heat pumps can operate under low-temperature environments, with some running smoothly in conditions as low as 30 degrees. But with many units, once you dip below 50 degrees, the pool heater will not be as effective at doing its job. Typically, it needs to be at least 60 degrees outside for an electric pool heater to function best.

Top tip: Using a solar cover on your pool heater is a neat DIY trick when regulating the temperature. This solar cover helps trap heat in your pool water, preventing it from losing heat. It also allows the pool heater to pump more efficiently because it’s operating in a warmer environment.

Check the Filter

If your pool heater is not getting enough water, then this could cause it to be faulty. Pool heaters rely on a steady stream of water to operate correctly, and when this is interrupted, you will start to run into issues. To make sure that your pool heater is getting enough water, you need to check your filter. A dirty filter filled with debris will keep your pool heater from receiving an adequate amount of water.

When checking your pool filter, make sure that you empty the skimmer and pump baskets weekly. This will prevent build-up. Also, make it a point to keep the filter media clean. Lastly, you want to ensure that you run your pump for at least 8 hours.

Take a Look at the Pool Pump

Your pool pump is responsible for the flow of water through your plumbing system, including the heater. If the pump is not operating correctly, it can cause issues with your pool heater. You must ensure that your pump is powerful enough for your pool system. If the pool pump isn’t strong enough, it may be unable to bring water into the heater with adequate pressure.

One easy fix is upgrading the pool pump to provide the necessary pressure. If you upgrade the pool pump, a variable-speed pool pump is a good option.

Variable pool pumps offer more power, longevity in operation, and efficiency compared to one- and two-speed pool pumps.

  • Single-speed pool pumps are the basic, most traditional type of pool pumps. They operate at a constant speed, are inefficient because of the high pumping speed, and can be quite noisy.
  • Two-speed pool pumps allow you to harness the efficiency of a lower speed, as it’s not recommended to use a high speed at all times. The higher speed option is best used with your heater and whenever you are cleaning your pool.
  • Variable-speed pool pumps use a permanent magnet motor, unlike the induction motor of one and two-speed pool pumps. This type of pool pump is highly efficient because you can set the exact flow rate you need. The result is a quieter unit that runs cooler, lasts longer, and is 90% more effective.

Use my pool pump sizing calculator to determine what size pump you need.

Inspect the Plumbing Valves

Troubleshooting your pool heater can be as simple as inspecting the plumbing valves. While this may seem a little silly, if your plumbing valves are set in the wrong direction, your pool heater will obviously not get the necessary water flow. Doing a quick walk-through of your plumbing valves and connections may lead you to find that an incorrect connection was made at some point.

Solving Common Gas Pool Heater Problems

Here are some common issues I’ve encountered before with gas pool heaters and how to solve them.

The Pilot Light

Your gas heater’s pilot light should always be turned on. So, if your gas heater isn’t working, your first step should be to check the pilot light – does it ignite? If not, it could indicate that the gas pressure is low, the heater isn’t venting properly, or the air getting to the heater isn’t great. If the pilot light is working, make sure the heater is turned on and the gas valve is in the “on” position.


Sometimes, the chemicals used to clean your pool water can damage the heat exchanger. It could just be a loose connection that needs to be tightened or colder winter temperatures, but you may also need to replace the heat exchanger.


If your pool heater pumps out dark exhaust, it could build up too much heat when it’s running. If this is happening, check the gas pressure and make sure your heater is venting properly.


Remember how I said your pool chemicals could damage the heat exchanger? Well, those same chemicals can also cause your heater to rust and corrode. You’ll want to replace those corroded parts to prevent further damage.

Replace Parts

If you have tried these simple steps to troubleshoot your power heater and can still not get it to function properly, this might indicate an internal issue with your unit.

There are different parts of a pool heater, including the high limit switch, pressure switch, motor, and heating element, that can be swapped out for a new one to get your heater running again. Replacing parts can significantly save costs as you’ll avoid purchasing an entirely new heater.

If you suspect an internal issue, it is best to get it professionally looked at before you do any work yourself. Tampering with your pool heater might void any unit warranties that could cover the costs of part replacements.

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What to Do If Your Pool Heater Is On But Isn’t Heating

As mentioned above, several things can cause your pool heater not to heat. This could be as simple as the heat not being turned up enough, or your pump valve could be turned the wrong way. On the other hand, it could be a more complex issue, such as a faulty power source or a pool pump with inadequate flow.

By following the above troubleshooting guide, you should be able to find the culprit behind your pool pump’s not heating when turned on.

What to Do If Your Pool Heater Is Overheating

Your pool heater should have a high-limit switch designed to prevent it from getting too hot, but if this switch is broken, your heater may overheat. It is important to address this immediately because an overheating pool heater can destroy it and even damage some of your other pool equipment.

If this is the case, you should check your switch and ensure it functions properly. You may need to call an electrician or pool professional for help.

Your pool heater can also overheat if the exhaust or air vents at the top of the heater are blocked and it cannot get proper airflow.

When to Call a Professional

While there are certainly many issues with your pool heater that you can troubleshoot and fix yourself, there may be a time when the problem surpasses your level of expertise. When this happens, I always recommend calling a professional. After all, pool heaters are complex machines, so the last thing you want to do is cause the problem to worsen. In general, if the problem is electrical or a complex motor issue, your best bet is to hire an expert for the job.


How Do You Know If Your Pool Heater Is Bad?

If your pool heater is turned on but isn’t heating, fails to turn on, or makes strange noises, there is likely an issue that needs fixing. If the heater is old, rusted, and worn out, it is likely time to replace the equipment.

How Long Do Pool Heaters Last?

The number of years that your pool heater lasts heavily depends on the type of heater. For example, electric heaters and solar heaters can last up to 30 years, but gas/propane heaters wear out much faster, lasting just 5 to 15 years on average.

How Do You Turn On a Pool Heater?

How you turn on your pool heater will depend on the exact model, but most have a control panel or display with a power button and temperature control buttons. If you aren’t sure how to use your heater, you can search “how to turn on (insert your heater model)” on Google.

At What Temp Does a Pool Heater Stop Working?

Most electric heaters tend to become less effective at heating water at temperatures below 50 degrees. That said, gas heaters and high-quality electric heaters can continue functioning at temperatures down to 32 degrees.

Fix Up Your Pool Heater

As with any unit with a running motor and electrical components, you are bound to run into issues with your pool heater at some point. If one of the above solutions doesn’t work, you may not have the appropriate size heater for your pool. The good news is, depending on the type of pool heater you have, the fix is usually a simple and straightforward one that you can remedy all on your own. For more on heaters, check out the articles below.

  • Gas vs. electric pool heater
  • How pool heaters function
  • Options for heating a pool
  • How long do pool heaters last?

Are you still having some issues with your pool heater? Feel free to drop me a line. I am happy to advise you further.

Pool Heater Troubleshooting: How to Fix Common Issues - Pool Research (2024)
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