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Not many people understand what happens when they flush their toilet, but behind the scenes, there’s an intricate wastewater system hard at work. In most cases, the wastewater travels through a series of pipes that are a part of a wastewater sewer system. Depending on where you live, there are two common systems that do this job: gravity sewers or force mains, also known as pressure sewer systems.

In this post, we’ll be taking a look at the differences and benefits of these two systems. We’ll delve into their inner workings and also explain what challenges they face.

Gravity Sewer Systems

Gravity sewer systems are perhaps the most common in areas that allow for it. These sewer systems rely on the natural force of gravity to move wastewater from higher elevations to lower elevations. They don’t require pumps or any extra equipment, and they typically consist of underground pipes with a slight slope, which facilitates the flow of wastewater.

Advantages of Gravity Sewer Systems

Gravity sewer systems have low operating costs because they don’t require mechanical plumbing equipment or additional systems. All they rely on is gravity, meaning the overall cost of keeping a gravity sewer system running is fairly low.

Another benefit is the lack of moving parts. Since there are fewer moving components in a gravity sewer system, it means that they require less maintenance and are less prone to mechanical failures. In other words, they’re more durable than other wastewater sewer systems and are ultimately more reliable.

Lastly, gravity sewers have a low environmental impact because they rely on nothing more than gravity to function. There’s no pump or system that requires electricity, and no fossil fuels are burned in the operation of a gravity sewer system.

Disadvantages of Gravity Sewer Systems

While simple and reliable, gravity sewer systems do have a few faults. The most glaring one is that it’s limited by topography. Properties that use a gravity sewer system are required to be at a higher elevation than the wastewater treatment plant, otherwise the entire system doesn’t work. This means that the pipes need to be installed in such a way that gravity allows the wastewater to flow downwards.

If the elevation doesn’t allow for gravity to move the wastewater, then pumps may be required. The addition of pumps to the system adds to the operating and building costs of a gravity sewer system, removing many of the benefits that we’ve mentioned above.

It’s also possible for groundwater to infiltrate gravity sewer systems. This causes increased flow rates when there’s rain or flooding, and this could potentially lead to overflow during days of heavy rainfall. This can cause raw sewage to overflow and may cause damage to the environment or create health risks.

Force Mains (Pressure Sewer Systems)

Force mains, also known as pressure sewer systems, use pumps to pressurize wastewater. It then travels through pipes to a treatment facility. Since it requires a pump, it’s more expensive to operate, but these costs can be offset with lower installation costs and more flexibility.

Advantages of Force Mains Sewer Systems

A force mains system can be installed in areas with challenging topography or in areas where gravity sewers don’t work. For instance, if the land is flat or the closest wastewater treatment facility is at a higher elevation, then gravity sewer systems aren’t a practical option, and force mains sewer systems should be used instead.

There are also lower installation costs because there’s no need to excavate large sections of land. The pipes are pressurized which means that gravity isn’t needed to move the wastewater.

And lastly, since force mains sewer systems are pressurized, they’re less susceptible to infiltration and inflow issues that gravity sewers face. Overall, these benefits make force mains sewer systems a lot more flexible to install, allowing them to be used in all types of situations.

Disadvantages of Force Mains Sewer Systems

Since a force mains sewer system requires a pump to function, it results in higher operational costs when compared to gravity sewers. This also leads to higher maintenance costs as well as a higher cost in terms of energy usage.

Having more moving parts naturally makes it more prone to leaks and failures as well. Pressure systems are far more complex than gravity systems, and there are more mechanical parts to understand, resulting in a higher chance of failure at many different points in the system.

And lastly, force mains systems are susceptible to leaking due to the stress of a pressurized system and higher maintenance requirements. This can result in environmental contamination if it’s not detected and fixed immediately. Whether you need help with designing, building, or maintaining a Force Main or Gravity Sewer, contact Muller today.