Why Does My Pool Heater Keep Shutting Off?

Use your pool heater in conjunction with a solar blanket.

A gas pool heater can make summer swimming more comfortable and extend the time you use your pool. This is especially true in the early summer when the temperatures are starting to creep up but are still low and late in the summer or early fall when temperatures are starting to come down.

Pool heaters can malfunction and stop working for a number of reasons. Cobwebs can block gas flow and can prevent the system from igniting or restrict gas flow causing the heater to turn on and off. The heater thermostat may malfunction or simply be set too low. If the heater has an igniter and it has broken, the heater may not be able to fire up at all. Poor water flow can also prevent the heater from operating properly.

Gas Heater Troubleshooting

Sometimes the most obvious answer is staring us right in the face and we can’t see it. A gas pool heater can malfunction for a number of reasons and often it’s a reason that we simply overlooked. Here are some common reasons pool heaters won’t work properly or at all, some of which I’ve faced myself and had to deal with:

  • Ensure the gas line is not shut off or that gas flow is otherwise restricted.
  • Ensure that any water lines to the heater are open to allow water flow.
  • Is the pilot light working? If the pilot light won’t start it may need to be replaced.
  • Our pool heater has an auto starter that should start the heater when we turn it on. But if the auto starter fails to work, the heater won’t fire up. Do you have a similar model as we do?
  • Ensure the heater power button is switched to the proper setting. Our heater has both a pool and spa setting but it only works on the pool setting. I made this mistake once.
  • Check that the thermostat is set high enough and hasn’t been set too low. The thermostat must be set higher than pool temperature or it won’t turn on to heat the water.
  • If the heater cycles on and off, check your water flow. Low flow may trigger the heater to shut off. Empty the skimmer and inspect pump basket to ensure nothing is clogging water flow.
  • Check and rinse/backwash your filter if necessary and look for leaks in the entire pool system. We’ve also had the aforementioned spider cob web problem that you may clean yourself or get professional help for.
  • Look for leaks underneath and around your heater to see if there is a problem that needs to be repaired. Depending on how old your heater is, repairs may not be cost effective.
  • Is it windy? Like with a barbeque, lit heaters can blow out if there is a heavy wind. Our gas heater has a wind stack to prevent this but not all gas heaters do.
  • Check to see that there is nothing blocking or preventing exhaust and there is no gas smell that could indicate a gas leak. We get leaves and small tree parts falling into our heater venting grates regularly.

In some cases, your own troubleshooting may fix the problem in question but in other cases, a visit from a gas heater professional may be in order.

Popular Type of Pool Heaters

Gas pool heaters aren’t the only type you can purchase. Here are the three main types to consider and some thoughts regarding each.

Gas heater

A gas heater requires a natural gas line from the house to the location of the heater. Chances are this will need to be added which comes at an extra cost the farther your heater and pool equipment are away from your house. Gas heaters are efficient and are the most popular option traditionally for pool heating. They operate in conjunction with the pool pump and can typically be run centrally through your salt water chlorinator, too. Gas heaters are the most direct form of heating in that they don’t rely on the sun or other external factor as both solar and heat pumps do for water heating success and provide on-demand heating.

Installed, a decent quality gas pool heater may cost $1,500 – $5,000 to purchase depending on the type, size and brand. Major brands include Hayward, Pentair, Intex and Sta-Rite. Costs may be higher if you need gas piping installed.

Solar heater

A solar pool heater requires the addition of solar panels typically on the roof of the house to heat pool water. The biggest downsides to solar heating are that you need direct sunlight otherwise it won’t work, the up front cost is expensive and it tends to involve piping running up and down the side of your house to the roof where the solar panels will sit. So it’s very noticeable and might be considered an eyesore for some people. It also tends to heat water slowly as it depends on the sunlight that it receives.

Installed, a solar heater may cost upwards of $4,000 but will last longer than a gas heater. You may need to replace your pool pump for a stronger one given that it will be pushing water up to the roof of your house. If you have your pool equipment at the back of your property away from the house like we do, the costs could be much higher.

Heat pump

A pool heat pump uses a compression system powered by electricity to heat pool water before returning it to the pool. While not as effective as a pool heater at heating water, it can be useful when solar heating isn’t an option. A heat pump tends to work well in hot climates but doesn’t work as well in areas that are cooler. It also requires the use of electricity which means you have to have power to the part of your backyard where the heater is located.

Installed, a pool heat pump may cost $2,000 – $5,000. They tend to last longer than gas pool heaters.

Pool Heater Efficiency

A gas heater with a natural gas line will tend to be the most efficient option in terms of heating your pool, maintenance and usability. A heater that works with a propane tank that needs to refilled is annoying when compared to a steady flow of natural gas from a gas line. Solar requires that you actually have direct sunlight so if you want to swim on a day with no sunlight, it won’t help. A heat pump also tends to work only in hot environments.

And a gas heater can be run 24/7 if needed. Yes, it’ll cost you but if you want the pool warm ahead of time, you don’t have to wait for sunlight and can fire it up as needed.

With a gas heater, you do also have to factor in the cost of a gas line if one isn’t readily available. You may require additional gas line work from a certified gas fitter to extend the existing gas line of your house to the area where your pool heater will sit.

Solar Blanket and Pool Covers

A solar blanket (pool cover) helps to not only retain heat at night, it uses the sunlight during the day to heat the pool further. If you know you are going to be using the pool in the afternoon on a particular day, putting the solar blanket on the night before and not removing it until shortly before pool usage will help to retain heat overnight and use the sun’s rays the next morning to heat the pool further before you are ready to use it.

Check out my complete page on solar blankets to learn more about this cost effective solution which works hand in hand with whichever heating option you choose. In some warmer environments you might find that purchasing a solar blanket on its own eliminates the need for a pool heater.


A pool heater can help to extend the pool season for you and provide on-demand warm(er) water especially if you choose a gas heater since it can be turned on at any time. Used in conjunction with a solar blanket, it will heat the pool and retain the heat when the pool is not in use. A solar heating option may be effective if you live in an area with significant direct sunlight as may a heat pump. But gas heaters using a natural gas line remain the most direct, reliable and on-demand option for heating a pool.

Carl Mueller

I bought a home with a salt water pool in 2006 and soon realized the benefits over traditional chlorinated pools. On this website I'll discuss all the tips and tricks I've learned over the years. I'll also help you troubleshoot various problems with pools in general and ones specific to salt water pools that I've experienced personally!

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