Your septic tank isn't the only part of your home's septic system that could cause problems. A failing drainfield can also put your septic system at risk of an expensive and time-consuming rebuild. Learn how septic system drainfields can fail over time and what you can do when these failures occur. How Drainfields Work Drainfields play an essential role in your home's septic tank system. After the solid waste and liquid effluent is separated within the septic tank, the effluent travels into the drainfield through a series of perforated pipes buried in gravel-lined trenches.