A residential and commercial hot water and steam boiler safety system and device that includes at least one hollow pipe, with one plugged or sealed end and a fitting on the other end for connecting the pipe in a substantially vertical mounting position, and at least one two float switch disposed in the pipe and electrically connected in series with a limit switch in the boiler, where the pipe is adopted for the flow and accumulation of water, so that float switch activates as the pipe fills with water and shuts off the boiler by turning off the gas valve, promoting safer boiler and steam boiler operation. Additional float switches positioned above or below in the hollow pipe may provide additional functions, such as a warning light and sound to the owner, or a notification via a telephone or cell phone system or through the home network or Wi-Fi system.