How to Know If Your Pool Heater Needs Repair

If you’ve set your heater to a specific temperature and the water is consistently falling short — or taking significantly longer to get there — this is one of the earliest and most reliable signs that something is off.

In gas heaters, reduced heating output often points to a partially clogged or scaling heat exchanger, a weakening igniter, or a gas supply issue. In heat pump heaters, it can indicate a refrigerant problem, a dirty evaporator coil, or a failing compressor. In Frisco’s hard water conditions, calcium scale buildup is especially common.

A gas pool heater that won’t ignite, or that lights briefly and then shuts off, is one of the most common heater repair calls. This behavior — sometimes called short cycling — is usually caused by a failing igniter, a dirty or faulty flame sensor, a problem with the gas valve, or a pressure switch issue.

Short cycling is particularly damaging because the heater is repeatedly attempting to fire, heating up components, and then shutting down — creating thermal stress that wears out internal parts faster than normal operation. A heater that won’t stay lit should not be left unaddressed.

Modern pool heaters display error codes when something is wrong. These codes should never be ignored or repeatedly cleared without addressing the underlying cause.

Common error codes across major heater brands (Hayward, Pentair, Jandy, Raypak) point to issues including: water flow problems, high limit tripped, ignition failure, pressure switch faults, service required alerts, and sensor failures. A heater that shows the same error code repeatedly after being reset has an unresolved problem that will only progress.

Water pooling at the base of your pool heater or moisture visible on the unit itself is a sign that something inside has corroded, cracked, or failed. The most serious cause of heater leaks is a damaged or corroded heat exchanger — the internal component through which pool water flows to be heated.

Heat exchanger corrosion is accelerated by imbalanced water chemistry — particularly water that is too acidic, has low calcium hardness, or has been highly chlorinated for extended periods. In Frisco, our hard water creates additional scaling risk.

A pool heater working harder than it should — due to scale buildup, a failing heat exchanger, a dirty burner, or a malfunctioning thermostat — will consume noticeably more fuel or electricity to produce the same amount of heat. Many homeowners attribute rising utility costs to general inflation without considering the heater as a possible cause.

A heater operating at reduced efficiency can add hundreds of dollars per season in wasted energy costs before the efficiency problem becomes obvious.

Rust or corrosion visible on the exterior of your pool heater — on the cabinet, vents, fittings, or around the burner area — is a warning that internal corrosion may already be advanced. External rust is almost always the surface expression of deeper deterioration.

Heavy white calcium or mineral scale is particularly common in Frisco due to our hard water. Scale that has built up inside the heat exchanger tubes dramatically reduces heat transfer efficiency and can eventually crack the exchanger under thermal stress.