How to Troubleshoot a Pool Heater

Having a pool heater is a great way to enjoy a warm dip in the pool as the summer months dwindle away. But what do pool owners do if they run into issues with getting that water to heat up? 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.
  • If you’ve tried troubleshooting your pool heater, but it is still not running correctly, you may need to replace some parts.

Check The Power

When you are working on troubleshooting a pool heater, one of the most common culprits is the power source. 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 that the pump is getting 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 would 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, then this can be an indication of 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 steps you will want to take.

Check The Temperature Settings

Most pool heaters are incredibly temperamental when it comes to the temperature you set it at and the outdoor 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 it is not warm enough, the heater will not run and keep up the water. There are different types of pool heaters, including gas and electric heaters, that will work just fine during cold weather, though some operate better than others.

Some heat pumps can operate under low-temperature environments, with some running smoothly 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 your pool heater to function the best way possible.

Setting a solar cover on your pool heater is a neat DIY trick to use when regulating the temperature. This solar cover helps keep your heater from losing any heat it generates during its run time. It also allows the pool heater to pump a lot 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 with a lot of blockage 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 the pump baskets weekly. This will keep build-up from happening. Also, make it a point to keep the filter media clean as well. Lastly, you want to ensure that you’re running your pump for at least 8 hours.

Take a Look at The Pool Pump

If the pool pump is not operating with enough power, this can cause your pool heater to have issues. A lot of times, when you first install a pool heater, the pool pump may not be strong enough to bring water into the heater with an adequate amount of pressure.

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

As opposed to one and two-speed pool pumps, variable pool pumps offer more power, longevity in operation, and efficiency.

  • 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.

To determine what size pump you need, use my pool pump sizing calculator.

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 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

First, 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 cause damage to the heat exchanger. It could just be a loose connection that you need to tighten or colder winter temperatures, but you may also need to replace the heat exchanger.


If your pool heater is pumping out dark exhaust, it could be building up way 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 cause damage to the heat exchanger? Well, those chemicals can also cause your heater to rust and corrode. You’ll want to replace those corroded parts to prevent any further damage.

Replace Parts

If you have tried these simple steps in troubleshooting your power heater and are still having no luck with getting it to function properly, then this might be an indication that there is 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 that there might be an internal issue, it is best to get it professionally looked at before you do any work yourself. If you tamper with your pool heater, you might be in danger of voiding any unit warranties that could cover the costs of part replacements.

Get My Free Pool Care Checklist

Download my free, printable pool maintenance checklist to help you accomplish regular pool care tasks for any type of swimming pool.

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Final Thoughts

As with any unit with a running motor and electrical components, you are bound to run into issues with it 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.

Have questions? Feel free to drop me a line.

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