If you're new to owning a septic system, you may not be aware that most of them are equipped with an alarm. As a homeowner, it is essential that you know what the alarm is for and how to deal with it if it should go off. Here's a look at the basics that you need to know. What is the Alarm For? Septic tank alarms alert you when water isn't flowing out of the septic tank and into the drain field the way that it should be.