How Often Should Septic Tanks Be Emptied (De-Sludged)?

Septic tanks are never completely emptied. Emptying an entire septic tank renders it ineffective by destroying the natural bacteria that decomposes your home’s waste. “De-sludging” is a term most plumbing companies prefer to use in place of ‘emptying’ because it more accurately depicts the actual process of maintaining your septic tank. De-sludging your septic tank is a process of removing solids and sediments from what is known as the “sludge” and “scum” layer of your septic tank. De-sludging your septic tank prevents potential problems from occurring while leaving enough liquid effluent to keep your septic tank working naturally and efficiently.

The EPA recommends that you have your septic tank inspected every three years and de-sludged according to the inspector’s assessment and maintenance suggestions. Most households find that their septic tank needs to be de-sludged once every 1-3 years. Knowing how many gallons your septic tank holds and accounting for the number of individuals in your household can help you estimate how frequently your septic tank will need to be de-sludged.

What is a Septic Tank?

When a home cannot be connected to a local sewer system, a septic tank is installed to collect and naturally decompose sewage and wastewater. According to the U.S. Census Bureau, 7% of housing units in large communities (more than 10,000 people) use septic tanks, while 50% of housing units in small communities (less than 10,000 people) use septic tanks or cesspools.

All sewage and wastewater from a house converge into one pipe that flows to a large underground septic tank. Upon entering the septic tank, all sewage is separated into three different layers: sludge, liquid effluent, and scum.

• Sludge

The heaviest sewage particles float to the bottom of the septic tank and create what is known as the “sludge layer”. This layer often takes the longest to decompose and thus needs to be de-sludged periodically to prevent massive build ups that can potentially cause problems.

• Liquid Effluent

The second layer is wastewater which eventually flows through a filter that removes smaller particles and drains the degraded wastewater into a drainage field or soil absorption system (SAS). The degraded liquid effluent enters the drainage field through a set of underground pipes with holes drilled in them and is naturally and safely absorbed into the surrounding environment.

• Scum

Finally, a layer composed of fats, oils, and protein form at the top of the tank. Additionally, this scum layer has to be maintained in order to prevent clogs in the filtration system.

Why Should Septic Tanks Be De-Sludged on an Annual Basis?

If your septic tank is not maintained every 1-3 years, the sludge layer will built up and slowly clog the SAS and cause sewage and wastewater to back up and come out your in-house drains. Additionally, the SAS can overflow and can result in a flooded yard and potentially run-off into nearby bodies of water. Cleaning up this mess and restoring your septic tank can cost thousands of dollars.