Burn marks at the bottom of the domestic hot water most likely indicates

• A. Water leak
• B. Gas leak in the supply line
• C. Overheating thermostat
• D. Flame roll out or backdraft

Answer: (D)

Burn marks at the bottom of a gas-fired domestic hot water heater point to an improper combustion problem, specifically flame rollout or a backdraft. When flames escape the burner area or venting is blocked, hot gases can be directed to the exterior, scorching the bottom and leaving burn marks. This signals a serious safety issue, often tied to venting blockages, inadequate combustion air, or a faulty burner. Other options don’t fit because a water leak wouldn’t create scorch marks, a gas leak in the supply line would typically show a gas odor and possibly a hiss rather than burning marks, and overheating of the thermostat usually causes other symptoms rather than exterior burn marks from flame exposure. If you see this, shut off the gas supply if safe and contact a licensed technician promptly.