How to Troubleshoot a Pool Gas Heater—Fast

You have pool heater because you like to swim in warm, relaxing waters—without worrying about your hair standing on end or your teeth chattering. But if you’re here, it means two things: First, that you use a gas heater to heat your pool water. And second, that it’s not doing too well right now. My only hope is that you realized it wasn’t working before you cannonballed right into your pool!

While a broken gas heater can be a nuisance, it’s also a fairly easy device to repair. I’ll explain how a gas heater works, where to look for the most common problems, and how to fix them.

And if you don’t want to do the repair, or if it’s looking like your gas heater is kaput? Here’s a silver lining: there’s a better way to heat your pool.

First, Know What You’re Up Against

Hate it break it to you, but although gas heaters are typically considered the most standard heater for pools, they’re also the most outdated. These are common heater types because they’ve been around the longest, and to be honest—they work in a way that is easy for us with stoves and radiators to understand.

Because of the, ah, technology of gas heaters, there are benefits and drawbacks to troubleshooting them. First of all, because they’ve been around for so long, it’s likely that you’ll have an older model in your backyard, which is more likely to break. The benefit is that because these are pretty simply made, your chances of fixing yours on your own is higher. That is, unless the wear is so bad that it’s beyond repair.

But the biggest con of gas heaters goes beyond breaking and fixing. The truth of the matter is that they’re the most expensive of any pool heater type. And I’m not talking price tag. While gas heaters aren’t cheap to buy, they’re even more costly to operate. They guzzle up energy because, unlike other pool heater types, they make their heat from scratch. So before moving on, think back to your last energy bill. Did it make your teeth chatter? Maybe it’s time to rethink your heater. My recommendation is the energy-efficient, powerful, and convenient pool heat pump.

Here’s How a Gas Heater Works

Since we’re about to troubleshoot its individual parts, let’s first debrief how a gas heater works. Basically, a gas heater burns either natural gas or propane inside a combustion chamber. As the pump circulates your pool’s water, the water drawn in travels through a filter through copper coils, which run through the combustion chamber. Then, the warmed water is returned to the pool. Exhaust that the burning gas emits leaves the chamber through a flue, sort of like a chimney.

Pretty simple, right? Now let’s troubleshoot that gas heater for you.

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How to Troubleshoot a Pool Gas Heater—in Seven Methods

To troubleshoot your pool gas heater, it’s best to start with the problem you’re currently facing and go from there. Again, these are fairly straightforward devices, so no need to inspect individual parts one by one.

The Pilot Won’t Ignite

This one’s pretty basic, but also one of the most common. If your heater isn’t igniting, and the pilot light isn’t turning on, there’s a few things that might be going wrong. The gas pressure could be low, the air supply could be poor, and the heater might not be venting properly.

First, check all the air vents to make sure they’re not blocked. Then, adjust the gas pressure if necessary.

These next tips are common sense, but I’m going to say them anyway just in case: make sure the gas heater is on, the gas supply valve is in the on position, and the thermostat is set to a temperature higher than the water itself.

The Heater Leaks

If your heater is leaking when the burner is lit, the leak is likely condenscendion that forms when heating up very cold water. That’s the easy answer, and not a problem you need to solve. But it can also be a result of excessive water flow or a damaged internal bypass. Installing an external bypass can reduce water flow into the heater.

If the heater is leaking when the burner isn’t lit, it might be that the chemicals you balance in your water every week have corroded the gas heater’s heat exchanger. Check to see if you have a loose connection or a leaky gasket. Otherwise, you might need to replace the exchanger.

The Heater Turns Off and On

If the heater is sporadically turning off and on, it’s likely that you have a water flow issue. Clean out the filter, check to make sure your valve is shut, and make sure your water connections aren’t reversed. If all checks out, it’s probably time to replace your thermostat.

It’s Not the Temp You Want

If your heater is not delivering the temperature you want, your thermostat is probably set too low. Check the temp of your water and compare it to the number you’ve set on your gas heater. It could also mean that your heater is too small for your pool (that’s why when buying a pool heat pump it’s important to look at the gallons each is specified to treat). It might also signal too little of the natural gas or propane that’s powering your heater. Additionally, it could be that the high limit switch is faulty.

This could also be occurring because you’re running the heater when it’s too cold outside. Gas heaters might have the reputation that they can run in any weather, but that’s simply not true—they’re subject to the weather just as much as their heat pump and solar heater counterparts.

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The Heater is Rusting

Finding rust in your pool while the heater’s running—in combination with these other issues or not? The culprit is likely a chemical balance thrown out of whack, which has then corroded some of the few parts of your heater. If you see any rust inside the unit, repace the parts that have turned brown.

The Heater Is Getting a Little Too Heated

Is your heater black on the top or expelling a dark exhaust? This means that your gas heater is excessively hot to the point of overheating itself. Check your gas pressure and make sure that the air vents aren’t blocked.

The culprit of your heater’s overheating could also be the wind. If this seems to be the case, install a high wind stack. This tool can help shield your gas heater from too much wind.

Once You Experience a Heater, There’s No Going Back

If it’s starting to look like the effort of the repairs isn’t worth it for your gas heater—or worse, that the heater is beyond repair—you’ve got two options: either get a new pool heater, or stop using a heater.

Actually you’ve got one option: get a new pool heater. Once you know what it’s like to use a pool heater, it’s hard to go back to shivering on the pool steps, or never knowing what to expect when you dive into the water. Chances are that since you’ve been using a pool heater, you’ve even been swimming longer. And if you have any especially young or elderly family members, you might even know that they require warmer temperatures to swim comfortably.

My advice? If you’re going to get another heater, make it an electric pool heat pump. You and your bank account will be thanking me for a long, long time—and a little more every single month. Because heat pumps are designed to compress heat, not create it from scratch, they dramatically cut the cost of your energy bills. In the case of this powerful ComforTemp Pool Heat Pump, for every $1 spent, it gives back $5 worth of heat.

Did you know high heat can compromise your sanitizer? Keep your sanitizer operating at its highest capacity by switching to a powerful automatic cleaner that works on its own: the Blue Torrent MyBot Inground Robotic Cleaner, which works powerfully to keep your walls and floor sparkling clean. As customer David Lain says, “Very pleased. My wife loves it.” Check out this user review to find out more.

You Can Take the Heat!

Whether you found an easy fix for your gas heater or you’re one step closer to the perfect pool heat pump, here’s to warmer, more relaxing future swims. You did the work, and you deserve a celebratory dip—with no icy surprises. Ahhhh. Enjoy.


Read more on whether you should run a pool heater overnight. Want to know how to heat your pool in an efficient way? Learn more here.