Pump runs but Rheem pool heater or heat pump does not fire when it should.

Safety First: Turn OFF pump and heater before adjusting plumbing or wiring.

• Increase pump speed: On variable‑speed Rheem pumps, raise RPM during heating cycles to meet the heater's minimum flow requirement.
• Check heater bypass: Ensure any bypass valve is set per Rheem heater instructions so adequate flow passes through the heater.
• Verify interlock wiring: Confirm the heater's fireman's switch or flow interlock is correctly wired to the Rheem pump control terminals.
• Clean heater strainers: Some heaters have internal filters or strainers; clean them to restore flow.
• Observe heater indicators: Check the heater's own display for flow or pressure faults that may point to inadequate pump output.