Sewer School: What is the Difference Between Septic and Sewer Systems?

Posted by Olivia Singer on Nov 6, 2020

Sewer systems and septic systems serve the same general purpose: providing a means for disposal of wastewater from homes and buildings to protect communities and ensure water quality. Both systems filter out black water and gray water, as well as bacteria and pathogens before the water is reintroduced into the environment.

But there are also some major differences between the two and each system comes with its own set of advantages and disadvantages.

Who’s Responsible for Wastewater? 

Septic System on a Property

Sewer systems connect many different homes and businesses to one centralized system. Wastewater travels through a lateral pipe on the individual property to join a network of other pipes which ultimately carry the wastewater to a facility for treatment. Sewer systems are maintained by the local public works department, though lateral maintenance is the responsibility of the property owner.

Septic tanks, on the contrary, are independent to the property they are located on. Wastewater moves from the home or facility into a holding tank where bacteria breaks down the solid waste and liquid effluent before it’s released into a drainfield. Septic systems are the responsibility of the property owner. 

Public Impact 

Because septic systems are the responsibility of the property owner, if there are issues, it’s likely due to the owner’s negligence. If properly maintained however, issues are typically few and far between and septic tanks may only need to be pumped out every few years.

In contrast, sewer systems are shared between many different homes and businesses, so one property’s negligence can greatly impact others. Decentralized systems reduce the risk for exposure to pathogens and disease transmission, according to the EPA. However, because sewer systems are maintained by a governing department rather than an individual, they are generally seen as reliable and robust.

Sewer System Anatomy

Septic systems are considered to be a more environmentally-friendly option over traditional sewer systems: removing pollution from the surface water, recharging groundwater and replenishing aquifers, the EPA states. They also help reduce the large infrastructure and energy costs required to collect and treat wastewater.  

Breaking Down Costs

There are pros and cons on either side in terms of cost. Property owners relying on a sewer system typically pay a monthly fee for wastewater services—which may be combined with their water bill—but are not responsible for maintenance outside of their home. Those with septic systems pay an upfront cost for the system itself and are fiscally responsible for any maintenance needed, but do not have to pay monthly fees. 

Today, both septic systems and sewer systems are used across the U.S.—their popularity varying greatly from state to state and between regions. The EPA reports that more than one in five households rely on septic over sewer—septic systems may be more prevalent in rural areas where there are fewer homes to connect to through a sewer system. Each comes with its own set of benefits and challenges. Broadly speaking, septic systems have fewer recurring costs to the owner if maintained properly, but sewer systems offer a higher level of convenience shifting the responsibility from the owner to the local public works department. 


For more information about sewer systems, request a free copy of our Sanitary Sewers poster breaking down the complex network of underground pipes and explaining how it all works together: 

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Topics: All Topics Sewer School