Rheem tankless water heater does not fire when a single low-flow faucet is opened

Safety first: Ensure unit is installed per Rheem specifications for minimum flow and pressure.

• Test with higher flow: Open multiple hot taps to see if the unit fires. If it does, the issue is low flow at individual fixtures.
• Clean inlet filter: Remove and rinse the cold inlet filter screen.
• Check aerators: Clean faucet aerators and showerheads to improve flow.
• Inspect flow sensor: If the unit still fails to detect flow, the flow sensor may be sticking and should be cleaned or replaced.