Boiler leaking water from bottom of cabinet

Safety first: Turn off power and close the water supply and isolation valves. Allow the boiler to cool before touching any components.

• Step 1 – Identify leak source: Remove the front cover and use a flashlight to trace water back to its highest visible point. Check around the heat exchanger, pump, relief valve, and all unions.
• Step 2 – Check pressure relief valve: Inspect the discharge pipe from the pressure relief valve. If water is dripping from this pipe, check system pressure. High pressure may indicate a failed expansion tank or fill valve.
• Step 3 – Tighten unions and fittings: Gently tighten any accessible unions or threaded fittings that are seeping. Do not overtighten plastic components.
• Step 4 – Replace failed components: If a gasket, relief valve, or internal fitting is cracked or corroded, replace it with Navien‑approved parts. Refill and purge the system, then check for leaks.

Significant leaks from the heat exchanger or internal manifolds should be addressed by a Navien‑authorized technician.