The Difference Between Septic and Sewer Systems

Did you know that plumbing processes have been in use for between five to seven thousand years?

Ancient engineers developed irrigation caverns to supply water to agricultural societies. As towns and cities grew, they began to use those caverns to redirect liquid waste away from settlements. The Romans are largely credited with having pioneered this technology ahead of The Dark Ages, when all progress towards the development of wastewater management systems ceased almost entirely.

Today, septic and sewer systems are our two primary wastewater management methods. Although both collect, process, and dispose of the harmful pathogens in human waste, there is one major difference between them: sewer systems are provided and maintained by municipalities, while septic systems treat wastewater on-site and are the responsibility of a private homeowner.

In a septic system, wastewater is directed from a home or facility into a septic tank, where solid and liquid waste is broken down and released into a drainfield, a network of perforated pipes laid in gravel-filled trenches. Drainfields typically measure between 18 and 36 inches wide and are located up to 100 feet underground, and without them, septic tanks would overflow and create unsanitary runoff. Wastewater flows into the soil through holes in a distribution pipe inside of the drainfield, destroying residual bacteria and sewage solids in the process. Septic systems are more common in rural areas, which typically lack centralized sewer systems.

Conversely, public sewage systems are connected to many homes and businesses. In a sewage layout, a network of pipes carry waste from lots to a municipal treatment facility, where it is purified before being released back into the environment. According to the Environmental Protection Agency (EPA) “the majority of Americans – or four in five households – rely on sewer over septic.”

Civil engineers are closely involved in the wastewater management process from beginning to end, providing designs for domestic or industrial treatment plants, pumping stations, and sewage systems and overseeing their construction; restructuring outdated layouts; and conducting feasibility studies for various wastewater-related projects. Civil engineers also prepare environmental documentation, help wastewater companies obtain the licenses and permits they need to operate, and collaborate with state agencies to ensure that treatment plants adhere to federal regulations.

For more information about the difference between septic and sewer systems, visit

Picture: Cloaca Maxima, one of Rome’s ancient sewer systems. Courtesy of Science Magazine.

Infrastructure Week, Day 4: Wastewater

Wastewater is the dirty little secret no one likes to talk about. Nevertheless, managing our nations wastewater is of the utmost importance.

No infrastructure plan is complete without wastewater management. It can impact the health of residents, strengthen or weaken the appeal of a locality, and have an effect on the environment.

As the nation’s population continues to grow, wastewater management has become increasingly crucial. Over the next 20 years, the U.S. is expected to gain more than 56 million wastewater treatment system users. This indicates the need for wastewater infrastructure improvements.

About 14,748 wastewater treatment plants currently serve nearly 240 million Americans, or 76% of the U.S. population. In its current state, our wastewater infrastructure suffers from 23,000 to 75,000 sanitary sewer overflow events every year, according to the U.S. Environmental Protection Agency. These facts demonstrate the need for increased wastewater infrastructure funding.

At KC Engineering and Land Surveying, P.C. (KC), our wastewater treatment group has designed, constructed, and helped to operate over 70 facilities. We work with government, industrial, and private clients to meet a full range of wastewater related needs. We approach each project with innovative and creative expertise to deliver comprehensive engineering services that solve the most intricate wastewater challenges from concept through design, construction, and operation.

With projects like the Tri-Municipal Sewer Commission Compost Permit Renewal, Wallkill Raw Sewage Pump Replacement, and Wappingers Falls Wappingers Falls Sanitary Sewer Pipe TV Inspections, KC has helped to increase capacity and improve the performance of existing treatment facilities. KC strives to meet strict water discharge policies, conserve energy, and reduce environmental impact.

The Sewer System’s Dirty Secrets

As a child, did you ever wonder where your goldfish went after you flushed him? Did you imagine him soaring off to sea through a single pipe that connected your toilet to the ocean? Probably.

Is that what really happened to him? Probably not. But don’t get too upset, the actual engineering behind wastewater and sewer systems is pretty interesting. In fact, your goldfish probably went on a wild ride! Whenever water or items go down the drain, they are sent through a pipe in the ground to the local sewer system. From there, gravity sends the wastewater down the sewage line towards the treatment plant.

However, most locations aren’t lucky enough to have a plant located at the bottom of a mountain. This is where the real engineering kicks in. Once the pipes get too deep, the wastewater must be pumped closer to the surface so that it can begin its descent again. These pumping stations are part of a force main sewer that pressurizes the water so that it can flow against gravity to the treatment plant at the other end.

Seems simple enough, but sometimes the lines will get clogged by miscellaneous items (like your goldfish) or rags that prevent the water from flowing. In these cases, a pig is sent from the beginning of the line to the end in order to remove the blockage. The pig is a flexible cylinder that moves through the pipes and clears any buildup or blockage it encounters. When the pig emerges from the other end, it brings all the waste with it. Check out this video titled “Sewer Wars” for an out-of-this-world description of the process.

When the water finally arrives at the treatment plant, chemicals and bacteria are used to cleanse the dirty water so that it can be sent back into the environment. After that, the cycle begins all over again.

Engineers use their skills to create complex systems that aid in the day-to-day process so seamlessly that most people don’t even know about them. But now that you do, maybe next time you’ll bring your fishy friend to the ocean yourself. That may be the one thing engineering can’t help you with.