Heater is leaking water from the bottom of the cabinet.

Safety first: Turn off power and gas. Hot water leaks can cause burns and electrical hazards.

• Identify source: Remove the front panel and carefully inspect with a flashlight while the pump is running. Look for drips at unions, headers, and the heat exchanger.
• Check unions and fittings: Tighten PVC unions at the heater inlet and outlet by hand, then slightly with a wrench if needed. Do not overtighten plastic fittings.
• Inspect heat exchanger: Look for signs of corrosion or green/blue staining on copper or cupronickel tubes. Persistent dripping from the exchanger area indicates internal failure.
• Differentiate condensate: In cool, humid conditions, some condensation is normal. Condensate is usually clear and appears only when the heater is firing.
• Replace damaged components: Replace cracked PVC fittings or unions. A leaking Thermeau heat exchanger typically requires full exchanger replacement.