Grease and Oil

Managing Grease and Oils in Your Septic System

Excess grease and cooking oils can cause serious problems for your septic system. When grease is washed down the sink—especially with hot water—it may seem harmless at first. However, as it travels through the sewer line, it cools and begins to solidify. This can lead to a hard buildup at the inlet tee or baffle of the septic tank, restricting flow and potentially causing backups into the property.
Grease can also temporarily re-liquify when hot water, such as from a laundry load, enters the system. This allows it to move through the tank, only to cool and solidify again further downstream, creating additional blockages.

Another common issue occurs when there is a low spot or “belly” in the sewer line between the house and the tank. In these areas water can collect allowing grease and solids to settle, cool, and harden over time—eventually leading to a blockage.

Grease-related problems can be even worse in systems equipped with filters, such as those at the outlet of the primary tank or in a lift station with a screened vault or Biotube Filter. These filters are designed to trap solids 1/8 inch and larger, as grease solidifies it can cling to the screen surface, reducing flow and causing the filter to clog prematurely.

Best Practice

The simplest way to prevent grease-related issues is to keep it out of your system entirely.