Takagi water heater does not start when a single low-flow faucet (e.g., modern lavatory) is opened.

Safety first: Water may be hot; use caution when adjusting fixtures.

Steps:

• 1. Increase flow: Open the faucet further or open a second hot tap to see if the heater starts.
• 2. Clean inlet filter and aerators: Remove debris from the cold inlet filter and faucet aerators to improve flow.
• 3. Check flow sensor: With water off and pressure relieved, remove and clean the flow sensor turbine.
• 4. Adjust or bypass mixing valve: If a mixing valve is installed, it may be throttling flow. Have a plumber adjust or reconfigure it to maintain sufficient flow through the heater.