Describe the sound and timing
Note whether popping occurs during heating, after a hot-water draw, when a fixture closes, or at another time. Save a recording from a safe distance without opening equipment.
Identify gas or electric equipment, model, age, and any change in hot-water delivery. Report visible leaks, unusual odor, soot, or signs of overheating promptly rather than treating them as routine noise.
Check the sediment finding
A. O. Smith's mineral-build-up bulletin describes popping from water trapped under deposits. That is one possible explanation; the sound alone does not establish it. A. O. Smith mineral-build-up guidance.
Ask what came out during flushing, whether flow was restricted, and whether the technician found deposits that remained. Request the exact heater's recommended care procedure.
Flushing and chemical deliming (using an approved treatment to remove built-up mineral deposits) are different work. A routine drain-and-flush visit does not establish that an approved deliming treatment was performed or needed.
Decide what deserves follow-up
Ask the provider to assess the reported sound, heater condition, relevant water conditions, and whether operation meets the equipment's requirements. Do not assume all popping is harmless or that every noise requires replacement.
If no fault is found and monitoring is recommended, request the reason and the changes that should prompt another call. If a correction is recommended, ask what finding supports it and how the result will be checked.
Do not add household acid or descaler, operate an unfamiliar drain valve, or open a burner or element compartment to investigate. Use qualified service for work beyond approved owner care.
Keep the care plan useful
Ask whether the schedule or procedure should change based on actual deposits and water conditions. A calendar interval alone does not show what the equipment needs.
Your next step is to send the sound timing and last service report to a qualified water-heater provider. Request a cause-based recommendation with a clear distinction between routine care, additional treatment, and repair.