Gas Pool Heater Troubleshooting

Swimming pool heaters are the most complicated piece of pool equipment on you pool equipment pad. Making repairs to pool heaters should be performed by qualified personnel. Gas pool heaters using Natural Gas or LP (Liquid Propane) gas can be hazardous by combustion or exhaust of the pool heater. Hayward pool equipment has created the Pool heater FAQ below to help the pool owner with pool heater repairs and pool heater troubleshooting. has all of your swimming pool heater parts for your Anthony, Purex, Coates, Hayward, Comfortzone, Jandy, Pentair, Raypak, Teledyne Laars/ Jandy, or Sta-Rite pool heater.

My heater will not ignite.

  1. Is the heater switch on?
  2. Is the thermostat set to a higher temperature than current water temp?
  3. Is the pump running with a clean filter?
  4. Is the heater gas valve in the on position?
  5. Is the heater pilot lit?
  6. Is the gas supply valve open?
  7. Are all plumbing and filter valves open?
  8. If a heater bypass is installed, is it properly adjusted?
  9. Contact a qualified technician if you still cannot locate the problem.

The pilot won't light?

This could be due to low gas pressure, inadequate air supply, or improper venting. Make sure gas is turned on; with propane, make sure the tank has fuel. Also check for water run-off from roof or sprinklers that may be flooding the heater. Check to make sure the heater pilot tubing is intact and not clogged.

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. You may want to install a solar pool cover to slow heat loss from your pool. All pool heaters have high limit switches to prevent overheating. A faulty high limit switch could shut off the heater, or the problem could be that the heater is truly overheating, perhaps from improper exhaust out of the top of the heater.

The heater cycles on and off before it reaches the desired temperature?

Your heater may have inadequate water flow due to a dirty filter, closed valve, external bypass, reversed water connections, or pressure switch out of adjustment. It is also possible that your thermostat is out of calibration or needs to be replaced.

Why do I need to frequently relight my pilot?

See previous two questions for additional information. Also check for water run off from above or sprinklers directed at heater. A high wind stack may be needed due to heater location.  Millivolt models have a thermocouple or pilot generator that may be faulty or weak. Loose or rusty connections of the thermocouple to the gas valve or loose coil connection, or a short in these wires can shut off a pilot.

I hear "clicking" or "sparking," but my heater will not ignite.

Review to the pool heater owner's manual. If you do not find your answer, turn the heater off and contact a qualified service company. Make sure that the gas valves are all in the on position, and if LP (Propane) is being used, check the gauge on the tank.

The heater is leaking water.

The pool heater heat exchanger may be leaking because of chemical or sanitizer damage. The damage may be from winter freeze - usually leaking upon spring start-up, and usually on the return manifold, aka rear header. There could be a gasket leaking, or a loose connection to the pressure switch.

The heater appears to leak only when the burner is lit.....

This may be caused by condensation (occurring when heating very cold water); a missing or damaged internal bypass in the front header; or excessive water flow through the heater from an oversized pump. Check the heat exchanger for sooting, and make sure the internal bypass is working. Install an external pool heater bypass if necessary to reduce the water flow coming into the heater.

Heater top blackened and/or emitting dark exhaust?

Either low gas pressure and/or inadequate air supply and venting. Review the installation requirements in the pool heater Owner's Manual.  Both conditions may need to be evaluated by a qualified service technician. This is called sooting and could lead to other problems or hazards.

The heater has damage due to excessive heat. Why?

One, or a combination of the following: low gas pressure, down-drafting, air supply, and venting. The pool heater may need a high wind stack, if installed near a vertical wall or windy area. Make sure that the heater is installed with proper clearances all around the outside. Pool Heaters can catch adjacent structures on fire, and pool heaters should not be located near windows, where carbon monoxide from the pool heater could be drawn into the house.

I have rust returning into my pool?

Sanitizers or chemical imbalance can deteriorate protective coatings on heater components and create rust. Usually the cast iron headers are the rusty culprit. Re-balance chemicals and replace any damaged components. Make sure any chemical feeders are installed after the heater, and place a check valve between the two to prevent backflow of highly chlorinated water into your pool heater.

My heater makes a whistling noise.

Low gas pressure can cause whistling in the burners. Check your Owner's Guide or contact your installer.

Do Hayward heaters need heat sinks or a fireman's switch?

No. Hayward heaters cool down immediately after shut down. It is however, good practice to turn off a firing pool heater in advance of shutting off the pool pump.

What should my heater be installed on?

All heaters should be installed on a non-combustible material, such as concrete or block. It must not have any structures above it, if installed outdoors, including tree branches within 4 feet. Consult owner's manuals for clearances around all four sides of your pool heater. 

Can Hayward heaters be installed indoors?

Yes, specific conditions apply. Please consult your owner's manual for complete details. Indoor pool heaters must be vented to the outside in a very specific manner, and have enough influent air to combust properly. Improperly installed pool heaters have the potential to cause fatalities from carbon monoxide emissions, or gas explosions.

How much fuel does my heater use?

Propane heaters use one gallon of fuel per hour for each 91,000 BTU's of heater input. Example: A 250,000 BTU heater uses: 250,000/91,000 = 2.75 gallon per hour. Natural gas heaters use one therm (100,000) BTU per 100,000 BTU's heater size. Gas invoices are usually billed by therms.

How can I save on my heating costs?

  1. Purchase an energy efficient heater model.
  2. Use a solar pool blanket or automatic cover on your swimming pool when not in use.
  3. Keep the temperature at the lowest comfortable position.
  4. Remember to not turn up the heater to maximum, (it will not heat any faster) But set it at a known setting for your desired maximum temp.
  5. Turn heater off or to a low setting during periods of non-use.
  6. Wind is one of the largest heat thieves. Fences or shrubbery can reduce the effect that wind will have on pool heat loss.

Other Tips to Economize on Pool Heating - from Teledyne Laars/ Jandy:

  1. Keep a thermometer in your pool. It will pinpoint accurately the temperature most comfortable for you.
  2. Keep your thermostat at the lowest comfortable setting. Each degree more heat than needed will add more to your monthly fuel cost and use up more energy than necessary.
  3. Mark the "comfort setting" on the thermostat dial. This will prevent accidental or careless over-heating and waste of energy.
  4. Lower thermostat to 70 degrees when pool is to be unused for three or four days. For longer periods, shut the heater off. You will save money on fuel consumption and help conserve energy.
  5. Protect your pool from wind. Wind above 3 to 5 miles per hour can lower the pool temperature substantially. A hedge, cabana or decorative fence can be an effective windbreak.
  6. Use a pool cover when pool is not in use. This can reduce heat loss by as much as 50%. If you are vacationing for a couple of weeks or shutting down for winter, turn the heater off completely, including any pilot light.
  7. Drain heater completely prior to freezing weather. Freezing water inside the heat exchanger can result in costly repairs.

Get a maintenance checkup annually. It’s your best ounce of prevention. Call your heater dealer for a skilled technician to do the job. The cost is minimal and the service will keep your heater working efficiently for many years. Keep your heater clean and as dry as possible. Investing in a winter pool heater cover is also a good idea to keep out the elements.