Heater runs but pool does not reach set temperature or heats very slowly.

Safety first: For gas adjustments, always use a qualified engineer. Do not modify gas settings yourself.

• Check pool cover: Use a thermal pool cover when the heater is operating to reduce evaporation and heat loss.
• Verify run time: Ensure the heater and circulation pump are running long enough each day to raise and maintain temperature.
• Clean filtration: Backwash filters and clean strainers to maximise flow through the Certikin heater.
• Compare specifications: Check the heater’s kW rating against pool volume and desired temperature rise; consult Certikin sizing charts.

If the heater is correctly sized but still underperforming, have a technician check for internal scaling, burner performance, and gas pressures.