The Most Common Swimming Pool Heater Problems (2024)

The Most Common Swimming Pool Heater Problems (1)

The Most Common Swimming Pool Heater Problems

August 8, 2018 Charlie Ramirez

Installing and troubleshooting a heater that is still under warranty without proper licensing can forfeit your warranty under the manufacturer’s terms and conditions. If your heater is out of warranty, sometimes, it’s simplycheaper to do it yourself. If you yourself in this scenario, this blog article is for you. In this blog article, we cover the most common swimming pool heater problems a pool owner might encounter and remediesto fix the issue.

My Heater Won’t Ignite

One of the most common problems with pool heaters is it failing to ignite.

Is your heater turned ON and the temperature set correctly?

  • Ensure that the thermostat is set to a higher temperature than the current water temperature.

Is your pump running with a clean filter and basket?

  • Inspect thepump and filter and clean if necessary.

Make sure that the pilot is lit (millivolt heaters).

  • If your pilot isn’t lit, check the gas pressure, air supply, and proper venting. Make sure the pilot tube is intact and not clogged. For MV heaters, if the pilot won’t stay lit, check the output on the thermocouple.

Is the gas supply valve in the ON position?

  • Without gas, the heater won’t operate. If the supply valve is OFF, turn it ON.

Are the plumbing and filter valves open?

  • Make sure to keep your valves open as to not prevent the water flow.

Low Water Flow

In order for a heater to operate smoothly and efficiently, it’s important that pool system maintains a consistent flow of water. Manufacturers equip swimming pool heaters with pressure sensors. These special sensors monitor and detect changes in water flow. For example, in some cases, you will see a “Low Water Flow” warning pop up on your heater’s LCD screen. Or, you might notice your heater isn’t pushing out as much warm water as it should or used to. Honestly, this is a very common occurrence. If you are experiencing low water flow, or your heater won’t start,ask yourself the following questions:

Have you cleaned yourfilter lately?

  • Monitor your PSI reading on your filter’s pressure gauge. If the PSI is too high, clean your filter.
  • Increasing pressure goes hand in hand with the decrease of water flow.

Is your pump basket dirty?

  • Check your pump’s strainer basket. Remove the basket and remove the debris with a hose.
  • Ensure thepump basket and lid are in good conditions. No cracks.

Do you have too many waterfeatures operating at once?

  • Your pool pump only moves a certain number of GPMs, therefore, too many water features can dramatically decrease your water flow.
  • If possible, replace the motor with a larger one.
  • Close water features, or alternate them, until the pool heats to the desired temperature.

Defective Pressure Sensor/switch (Most Common)

  • The purpose of the pressure switch is to ensure that water is flowing through the unit before it allows the heater to turn on.
  • The pool pump must be ON and your filter clean for the switch to close and allow voltage to pass through.
  • Test the voltage reading on thepressure switch with a multimeter.
  • Replace the pressure switch if necessary

Are you using the low settings on your variable speed pump?

  • For operation, heaters require a minimum GPM flow. If you are running your variable speed pump on the low setting, make sure you meet the minimum GPMs for your heater.

Pool Heater Turns ON and OFF (Cycles)

If your swimming pool heater is cycling ON and OFF, it is an early indication that the electrical connection or power supply is experiencing issues. However, it isn’t ALWAYS the case. There are other factors that can actively contribute to your heater’s ON and OFF cycles.

Is your pool water chemistry consistently and accurately balanced?

  • Poor water chemistry is one of the leading causes of equipment failure, especially pool heaters.
  • Test your water before adjusting your chemical levels. If unsure, please refer to the heater’s manual for the recommended chemical levels.

Have you inspected the pressure sensor, thermal regulator, and/or the high limit switch?

  • Inspect these parts for corrosion, scaling, and/or any electrolysis issues.
  • If thepressure sensor, thermal regulator, or high limit switch is faulty, corroded, or defective- replace it.

Have you cleaned your filter?

  • A dirty filter can cause low pressure and as a result, cause the heater’s pressure switch to turn OFF. A dirty filter can prevent a heater from firing and it can also cause your heater to shut off before warming the water to the desired temperature.

When’s the last time you have inspected and cleaned the heat exchanger?

  • Deterioration of the heat exchanger can impact your heater’s operation. Inspect your heat exchanger for chemical or sanitizer damage.

Pool Heater Isn’t Heating

Sometimes, your pool heater ignites but doesn’t reach the desired temperature. Or, maybe your heater isn’t generating heat at all. Both situations are very common.

Inspect your temperature sensor.

  • Make sure you have installed the temperature sensor correctly and it is in good condition.

Double check your thermostat settings

  • Set your thermostat to a higher temperature.

Did you properly size your pool heater?

  • If your heater is undersized, it will have problems heating your pool up. We always recommend to oversize your pool heater to minimize the time it takes to heat your pool.

The Most Common Swimming Pool Heater Problems (2024)


Why is my pool heater not reaching the set temperature? ›

Heater won't reach the desired temperature? The thermostat may be set too low. If the heat loss is greater than the heater input - the heater may be too small, outside air temperature is too low, or your heater may have an inadequate gas supply.

How do I reset my pool heater? ›

Reset your pool heater by flipping the breaker switch in the electrical panel to “off” and then “on.” Your breaker may be located in a disconnect box near your pool heater or in the breaker panel in your home.

What causes a pool heater to go bad? ›

There could be low gas pressure, poor ventilation, inadequate air supply, or another problem with the gas line. Insufficient gas supply is often to blame.

What would cause a pool heater to not ignite? ›

Tripped circuit breaker: The most common reason for a pool heater not turning on is a tripped circuit breaker or blown fuse. Check your breaker box and reset any tripped breakers or replace any blown fuses. ✓ Low water flow: If there isn't enough water flowing through the heater, it won't turn on as a safety measure.

How do you know if your pool heater is bad? ›

A well-functioning pool heater should operate quietly in the background. If you start hearing weird noises like banging, clanking, or whirring, it's time to investigate. Unusual sounds could be a sign of mechanical problems, loose components, or mineral buildup within the heating system.

Why is my heat pump running but not heating my pool? ›

Check that your heat pump is getting sufficient water flow.

Without constant, sufficient water flow, your heat pump cannot transfer heat from the refrigerant to your swimming pool. Insufficient water flow will not only lengthen your heating time, but also cause damage to your heat pump's internal components.

Can a pool heater get clogged? ›

Your pool heater contains a filter that prevents contaminants from circulating through the filter and causing a problem. However, if the filter becomes clogged, it can prevent the correct amount of water from passing through. Without sufficient water pressure, your heater won't be able to work.

Why is my Hayward pool heater not heating? ›

It could be due to less obvious issues. Low gas supply, failing pilot generator, a bad gas valve, slight blockage in the pilot assembly. If you are unable to light the pilot, visit your local Hayward dealer for guidance.

How many years should a pool heater last? ›

Often you need to replace a few essential parts, not the entire heater. Things like your climate, water chemistry, and maintenance habits will impact the lifespan of your pool heater. Pool heaters will last anywhere from 10 to 25 years. Gas pool heaters have the shortest lifespan, at 5-10 years.

What maintenance does a pool heater need? ›

Inspecting the unit: The pool heating unit should be inspected periodically to check for any leaks, cracks, or other signs of damage that may affect its performance. Checking the thermostat: The thermostat should be checked regularly to ensure that it is functioning properly and maintaining the desired temperature.

How do I know if I need a new pool heater? ›

The telltale signs to look for
  1. The pool heater is corroded and rusty.
  2. The heater won't start.
  3. The pool water is not getting warm enough.
  4. The heater is making a weird noise.
  5. The heater turns on and off frequently on its own.

Why is my heater not working in my pool? ›

The most common cause of swimming pool heaters refusing to start up is a dirty swimming pool filter. A dirty filter or pump basket can restrict the water flow so much that the heater simply can't work.

Why is my pool heater not flowing? ›

A dirty pool filter wins for the most popular water flow issue on a heater service call. Luckily, it's also the easiest one to diagnose and fix. You can overcome this issue by having a pool heater service tech or pool specialist remove the filter and run the pump again without a filter in.

How long does it take for a pool heater to raise temperature? ›

On cooler spring days when you still want to go for a swim, you might be wondering how long you'll be waiting for your pool to heat up. The answer varies (about 8-12 hours), and several factors influence how long it takes to reach your desired swimming temperature.

What temperature should a heated pool be set at? ›

The water temperature you desire for your swimming pool not only affects the size of the pool's heater, but also your heating costs if use a gas or heat pump pool heater. Pool water temperatures typically range from 78ºF to 82ºF. The American Red Cross recommends a temperature of 78ºF for competitive swimming.

How do you test a pool temperature sensor? ›

Testing. The sensor can be tested with a multimeter. It should read 10,000 ohms at 77F (25C) degrees. You can lookup other test values in the Temperature vs Resistance Conversion Chart for 10k Thermistors.

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