Before you call
A gas pool heater that does not start can have several causes. The useful first step is to describe what changed, not to guess which part failed. A short record helps a qualified technician look at the heater and the circulation system together.
Safety comes before the checklist
If you suspect a natural-gas leak, leave the area immediately. From a safe location, call 911 and your gas utility. For Southwest Gas, call 877-860-6020, whether or not you are a customer. Do not return to the equipment pad to collect a model number or test the heater.
For other symptoms, keep covers in place. Pentair's MasterTemp user and installation guide says service troubleshooting belongs to qualified, trained technicians. This article is a call-preparation guide, not a repair sequence.
Note what the display and pool are doing
From a normal, safe viewing position, write down the heater brand and exact model if you already know them. Note any message or code exactly as displayed and when it appeared. A close-up photo of the front display can help you share the exact message. A code is a clue for a technician; it is not a diagnosis on its own.
Tell us whether the circulation pump appears to be running, whether the pool or spa was selected, and whether a schedule or automation change happened recently. Pentair's guide points technicians to pump operation, water flow, valves and time clock settings when investigating a MasterTemp. You can report what you observe without moving valves or changing settings yourself.
Also note whether the heater never started, started and stopped, or ran without reaching your intended water temperature. If you noticed an unusual sound, water around the equipment or an interruption to other equipment, describe that too. The time of day and your intended swimming schedule help put those observations in context as Phoenix and Scottsdale nights cool.
Bring the whole system into the conversation
A heater depends on circulation and on the property's gas supply. Tell the technician if the filter was recently serviced or if another pool component changed, but avoid assuming that timing proves the cause. The exact model and site conditions matter more than a generic online error-code list.
If you are still deciding whether gas heating suits your pool, our MasterTemp overview explains the technology. If you are planning a new installation, read the separate guide to gas meter and supply capacity. For a heater that has stopped, contact Haoly Pools with the observations above so the right professional can assess the equipment.
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