Yes. Many materials that might be poured down the drain do not easily decompose. This can be harmful to the healthy bacteria that grow in your septic tank and drainfield to help break down organic matter. Do not pour grease such as: fats, butter, wax, cheese, & heavy cream. Liquid wastes such as: pesticides, drain cleaners, household chemicals, paints, paint thinners, oils or coffee grounds should also not be poured down the drain. If you have a garbage disposal, limit its use because food waste can add an unnecessary amount of solid material to your septic tank.