The answer to 'why is my septic tank rusty water' is that a rusty septic tank can be caused by the natural aging and corrosion of the metal components over time. This is a common issue with older septic systems. The rusty water is a sign that the tank itself or the pipes connected to it are starting to deteriorate.
Some common causes of a rusty septic tank include the use of harsh chemicals, high levels of acidity in the wastewater, and exposure to moisture and oxygen. Over time, these factors can cause the metal in the tank to corrode and rust, leading to the discolored water. In some cases, the rust may also be a sign of a more serious issue, such as a crack or hole in the tank.