Inspecting swimming pool heating systems during a home inspection is largely a visual, operational, and safety review of the heater, controls, and related plumbing and electrical components, without disassembly or technical servicing.

Scope and limitations

  • Verify presence, type, and basic operation of the heater (gas, electric, heat pump, or solar), but do not perform internal service, combustion analysis, or refrigerant work.
  • Inspect only readily accessible and visible components; do not remove burner assemblies, sealed panels, or perform pressure tests on plumbing.
  • Report observed defects, safety concerns, and recommend further evaluation by a qualified pool/spa contractor or HVAC/pool heater technician when conditions appear unsafe or performance is questionable.

Identification and documentation

  • Identify heater type (gas-fired, electric resistance, heat pump, solar-assisted, or combination) and whether it serves the pool, spa, or both.
  • Note manufacturer, model, approximate BTU or kW rating, and visible nameplate data when accessible and legible.
  • Document location (equipment pad, wall-mounted, rooftop for solar manifolds, etc.) and proximity to structures, openings, and combustible materials.
  • Record whether the heater responded to normal operating controls (thermostat or automation) and whether heating appeared functional at the time of inspection.

Installation and clearances

  • Confirm the heater is on a level, stable, non-combustible base or pad, not directly on soil or combustible decking.
  • Check that required clearances to walls, overhangs, and combustibles appear to be maintained around cabinet and vent/stack, based on manufacturer labeling and typical gas appliance practice.
  • Verify heater is installed downstream of the pump and filter in the circulation system and that appropriate check valves are present where required (e.g., between chlorinator and heater, or in systems with solar).
  • Look for evidence of improper installation such as makeshift supports, undersized flexible gas connectors, or unprotected electrical runs.

Combustion gas heaters (natural gas/propane)

  • Inspect cabinet exterior for corrosion, rust streaking, soot deposits, scorch marks, or melted components that can indicate overheating or combustion/venting problems.
  • Check gas piping for rigid, supported installation with a shutoff valve near the appliance, and look for corrosion, mechanical damage, or makeshift fittings; if a gas leak is suspected, recommend immediate service and do not operate further.
  • For units with a visible burner inspection port, observe the flame pattern only if safely visible: flames should generally be stable and mostly blue with minimal yellow tipping; heavy yellowing, lifting, or sooting is a defect needing service.
  • Verify the vent or flue is present where required, appears properly routed and supported, and shows no obvious rust-through, separation, backdraft staining, or termination under eaves or openings.
  • Note any combustion air concerns such as enclosure of an outdoor-rated heater, tight sheds without louvers, or storage of pool chemicals directly adjacent to the heater, and call these out as safety issues.

Electric resistance heaters and heat pumps

  • Confirm proper weatherproof electrical disconnect is present and accessible near the heater or heat pump, and that conductors are in raceway or listed cable with intact insulation and fittings.
  • Look for cabinet damage, missing covers, rust, or signs of overheating such as discoloration or melted plastic at terminals or contactors.
  • With the unit operating, listen for abnormal noises (grinding, rattling, loud buzzing) that could indicate failing fan motors, compressors, or contactors.
  • Verify heat pump airflow is unobstructed: clear vegetation, walls, and overhangs from intake and discharge sides per data plate guidance when visible.
  • Note that heat pumps typically warm water more slowly than gas heaters and perform best in moderate ambient temperatures; report if unit fails to start or if there is no noticeable temperature increase over a reasonable test interval.

Solar pool heating components

  • Identify presence of solar collectors (usually on roof or rack), associated supply/return piping, and solar control valves and sensors.
  • Confirm PVC or other piping is adequately supported, aligned, and free of obvious leaks, cracks, or heavy UV deterioration at exposed sections.
  • Check that the solar system is plumbed as a loop downstream of the filter and that appropriate check valves are present to prevent reverse siphoning or cross-flow when the solar system is off.
  • Operate the solar control (if conditions and controls allow) to see if valves redirect flow to the solar array and back without obvious leakage or abnormal noise.

Thermostats, controls, and automation

  • Locate and identify the heater's thermostat or temperature setpoint device, whether on the heater cabinet, at a remote panel, or via automation system.
  • Verify controls are labeled and accessible, and that the heater only fires when there is adequate water flow (pump running) and a call for heat.
  • Observe the heater cycling on and off with control changes if feasible: for example, raising the setpoint to command heat, then lowering it to terminate heater operation.
  • Note any indications of bypassed safety interlocks, such as jumpers on pressure or flow switches, taped-over fault lights, or evidence of tampering, and call for immediate professional evaluation.

Plumbing, valves, and circulation through heater

  • Inspect visible piping to and from the heater for leaks, mineral scale buildup, corrosion, UV deterioration, or amateur repairs (unions missing, unprimed solvent welds, flexible hoses not rated for pool use).
  • Confirm presence of necessary check valves and bypasses around the heater, especially where chemical feeders or solar loops are installed, to reduce backflow of highly chlorinated water or prevent stagnation.
  • Look for signs of restricted flow such as noisy heater operation, frequent cycling, or obvious kinking or undersized piping that may impair heater performance.
  • Report any visible leaks at unions, manifolds, or heat exchanger connections and note that leaks can cause internal damage and efficiency loss if not corrected.

Electrical safety, bonding, and grounding

  • Check that the heater and associated pump motors, blowers, and metallic components appear to be bonded together with a continuous copper bonding conductor where accessible.
  • Verify presence of equipment grounding conductors at the heater and associated electrical equipment, and look for loose, corroded, or disconnected grounding lugs.
  • Operate any accessible GFCI devices serving the heater circuit (where present) using the test button and report failure to trip/reset as a defect.
  • Note any unprotected splices, open junction boxes, or extension cords used to power pool equipment, and call these out as safety hazards requiring correction by a qualified electrician.

Operational checks and performance observations

  • With the circulation system running, activate the heater via its normal control and verify that it turns on and remains on without abnormal noises, odors, or visible problems.
  • If practical within inspection time, confirm that return water temperature at the pool or spa feels measurably warmer after the heater has run for several minutes, understanding that large pools and heat pumps may show only modest short-term change.
  • Observe the unit for error codes, status lights, or lockout indications on the control panel and document any displayed faults.
  • Explain in your report that you did not verify internal condition of heat exchangers, burner assemblies, or refrigerant charge and that long-term performance cannot be guaranteed from a single-day inspection.

Common defects to call out

  • Heater not operational from normal controls, short-cycling, or shutting down with visible fault codes.
  • Corroded, leaking, or heavily rusted heat exchanger/manifold connections; active water leaks at heater cabinet.
  • Sooting, scorch marks, or heavy rust on gas heater cabinet or vent, suggesting combustion or venting issues.
  • Missing or inadequate bonding/grounding of heater and associated equipment.
  • Inadequate clearances, improper mounting surface, or heater installed in an unventilated enclosure contrary to labeling.
  • Bypassed or tampered safety controls, unprotected electrical wiring, or gas piping that appears unsafe.