How long should you wait to check for spillage at a hot water heater or furnace after firing?

Waiting for 2 minutes after firing a hot water heater or furnace before checking for spillage is necessary because it allows the appliance to reach a steady operating condition. In that time, you can effectively observe whether combustion gases are being vented properly and if any spillage occurs.

During this brief period, the equipment adjusts to normal operating temperatures and pressures, providing a more accurate assessment of its performance. Spillage can occur immediately after ignition due to initial cooling or drafts, but a consistent evaluation requires a few moments to ensure the appliance is functioning as intended. This practice helps in identifying issues that may lead to unsafe conditions, such as backdrafting of flue gases into the living space.