The causes of these clogs are almost exclusively human error. The most prevalent culprit is the disposal of inappropriate materials. Modern society has created a misconception that many items are "flushable," when for a septic system, they are anything but. Wet wipes, feminine hygiene products, paper towels, and cat litter do not decompose quickly; they tangle and mat together, creating a physical blockage that even the most robust bacteria cannot penetrate. Furthermore, the kitchen sink acts as an accomplice to the crime. Pouring cooking grease and oil down the drain is a common mistake; while liquid when hot, these substances cool and solidify in the pipes and tank, creating a thick, concrete-like sludge that restricts flow. Additionally, the use of harsh chemical cleaners, bleach, or antibiotics can kill the beneficial bacteria necessary for decomposition, halting the digestion process and leading to rapid solid accumulation.

A septic tank is a living ecosystem of bacteria designed to break down organic waste. Anything that disrupts this balance or physically blocks the pipes will cause a backup.

: Bubbling noises coming from the plumbing when you flush or run water.