A pool heater that fails at the first cold snap of the season almost always had a warning sign that was missed during the previous year. Pool heaters fail in predictable patterns: burner blockage (spiders and debris), igniter degradation, heat exchanger scaling, and pressure switch failure. An annual inspection and service of each component costs 45 minutes and prevents most of these failures entirely. Here is the procedure.
Before opening any heater panel, shut off the gas supply at the shutoff valve closest to the heater. Do not rely on the heater's internal off state — close the supply valve. Wait at least ten minutes after the last operation before opening internal panels, as combustion components retain heat. If you smell gas at any point, stop, ventilate, and call the gas utility or a certified technician before proceeding.
Never work on gas connections yourself unless you hold gas service certification in your jurisdiction. Pool service techs can clean, inspect, and report — but gas line work requires a gas-certified technician.
The burner tray is the most common maintenance point on any gas pool heater. Remove the heater door panel (typically 4–6 screws) to access the combustion chamber. You will see the burner tray — a rectangular metal frame holding multiple burner tubes with orifices for gas distribution.
Use compressed air at low pressure to blow out each orifice. A thin wire or small drill bit can clear stubborn blockages — work gently to avoid enlarging the orifice, which changes the gas/air ratio. Wipe the burner tray with a dry cloth and inspect each burner tube by holding it up to light — you should see light through each orifice clearly.
Pool heaters use either hot surface igniters (silicon nitride elements that glow orange-hot) or intermittent pilot igniters (a spark electrode). Identify which type your heater uses before the inspection.
Inspect the igniter element visually. Cracks, chips, or carbon tracking on the surface indicate it is close to failure. Do not touch the element with bare hands — skin oils create hot spots that reduce service life. If the igniter is over three years old and the heater is having ignition problems, replace it proactively. Typical cost is $25–$60 for the part.
Inspect the spark electrode and ceramic insulator. The electrode gap should be 1/8 to 3/16 inch from the burner ground. Check the ignition wire for cracked insulation and the connection at both ends for corrosion.
The heat exchanger is the copper tubing that transfers combustion heat to the pool water. On most residential heaters, you can see the tubes through the burner section after removing the burner tray. Inspect for:
Calcium scale inside a heat exchanger reduces heat transfer efficiency and causes the high-limit switch to trip frequently as the exchanger runs hotter than designed. A severely scaled heat exchanger on an improperly balanced pool can fail within 2–3 seasons.
The pressure switch ensures the heater only fires when adequate water flow is present. Test it by starting the heater normally, then partially closing the return valve to simulate low flow. The heater should shut down within a few seconds. If it does not, the pressure switch is stuck closed and must be replaced — it is a critical safety device. If the heater refuses to fire even with correct flow, the switch may be stuck open or miscalibrated.
| Component | Check | Action |
|---|---|---|
| Burner orifices | Clear of debris/webs | Blow out with compressed air |
| Burner tubes | No corrosion holes | Replace if pitted through |
| Igniter | No cracks; correct gap | Replace if over 4 years old |
| Heat exchanger | No visible scale or green corrosion | Chemical descale or report |
| Pressure switch | Correct operation | Replace if stuck or erratic |
| High limit switch | No nuisance trips | Investigate cause before reset |
| Bypass valve | Smooth operation | Lubricate if stiff |
| Combustion air screen | Clear of debris | Clean with brush or air |
Log every heater service, note igniter age, and set a reminder for next year's annual. PoolLens works offline so you have access on every pad, no signal required.
Open PoolLens Free →White or gray deposits on the copper tubes, restricted flow through the heater, and a heater that trips the high-limit switch frequently are all signs of heat exchanger scaling. A pro can confirm by measuring the temperature differential across the heater — excessive delta-T indicates restricted heat transfer.
Silicon nitride igniters typically last 3–5 years. Hot surface igniters fail suddenly rather than gradually — they work fine until they do not. If a heater is over three years old and fails to ignite, the igniter should be the first component inspected.
Yes. Yellow sac spiders are specifically attracted to the gas odorant in propane and natural gas lines. They build webs in the burner orifices and gas valve venturis, causing partial or complete blockage. This is one of the most common causes of intermittent heater ignition failure and is entirely preventable with annual cleaning.
Gas connections and combustion components should only be serviced by certified pool/gas technicians in most jurisdictions. Cleaning burners and inspecting the heat exchanger visually is within scope for trained pool service professionals. Replacing gas valves or working on the gas supply line requires gas certification.