Septic Tank vs. Sewer Lines: What’s the Difference?

Do you know where your wastewater goes after it leaves the sink, toilet, or shower? Whether it’s filtered through your backyard or piped away underground by the city, the system behind it matters—and it can impact your budget, maintenance responsibilities, and the environment.

If you live within city limits, you are likely connected to the municipal sewer system. If your home is in a more rural area, you may have one of the 1.2 million septic tanks in California instead.

There are several differences between septic and sewer systems. Here’s everything you need to know about the pros and cons of septic vs. sewer, and when to call a plumber for either system.

What Is a Septic Tank?

A septic tank is a large, watertight container buried underground on your property. Modern septic tanks are typically made of durable materials like concrete, fiberglass, or plastic polymers. In older properties, the tank may be an older model made of steel instead.

A septic tank stores and processes wastewater from a home or commercial building, such as a restaurant. The property’s drain lines connect directly to the tank, where the wastewater is stored until it is separated into different layers of substances. These layers are then treated in different ways to keep the tank in proper working order.

How Does a Septic Tank Work?

Septic tanks use natural processes to treat wastewater. Here’s how it works, step-by-step:

• Wastewater entry. All wastewater in your home travels from the drains to a main drainage pipe, which connects to the septic tank.
• Separation process. Once inside the tank, the wastewater is stored over long periods, during which it separates into three layers: scum, sludge, and greywater.
  Scum contains oils, greases, and other light materials that float to the top of the water. Sludge is the layer of heavier solids that falls to the bottom of the tank. Greywater is everything else that remains in the middle of the tank.
• Bacteria break down. Naturally occurring bacteria break down the scum and sludge layers, partially treating the wastewater.
• Discharge to the drain field. When new wastewater enters the tank, the partially treated wastewater is pushed into a drain field through an outlet pipe. The drain field connects to the soil, filtering harmful bacteria from the wastewater.
• Regular maintenance. Over time, scum and sludge layers build up. They must be periodically removed from the tank to prevent it from failing or contaminating the ground.

When comparing septic vs. sewer, septic systems are typically considered more complex. However, they are generally reliable and have a long lifespan—up to 40 years with professional plumbing and tank maintenance.

Septic Tank Pros vs. Cons

Below is a table comparing the advantages and disadvantages of using a septic system vs. sewers for your wastewater needs:

What Are Municipal Sewer Lines?

Municipal sewer lines are city- or county-managed pipes that collect wastewater from homes, businesses, and other properties. In most communities, these pipes transport the wastewater to a local treatment plant.

Home and business owners are not responsible for maintaining or repairing sewer lines, except for the connecting elements on the property. These elements are collectively referred to as the “lateral” and include the wastewater pipes inside the building and the connection point to the municipal lines.

Sewer Line Pros vs. Cons

Here is a comparison table of the pros and cons of using public sewers vs. septic tanks to handle your property’s wastewater:

Reach Out to a Professional Plumber

All wastewater management systems require maintenance, whether your home or commercial building is connected to the municipal sewers or a septic tank. Your property’s piping or lateral connections may clog, develop leaks, or weaken over time without regular attention. If you operate a septic tank, you must verify that it is in proper working order and not leaking untreated wastewater into the ground.

Do you need lateral piping or septic system repairs? Contact an experienced plumber in your area. Licensed plumbers in California are legally allowed to inspect, install, maintain, and repair both systems.

FAQs

Are sewers and septic systems the same?

No. Sewers are the city or municipal pipes that transport wastewater from homes and commercial buildings. Septic refers to individual septic tanks installed on property, which treat and store wastewater in a tank that must be periodically emptied.

Is it better to have a septic tank or a sewer line connection?

It mainly depends on your property type and whether you are close to a city’s wastewater network. According to California law, if your home or commercial building is within 200 feet of a city or county sewer system, it must be connected to the local sewer lines.

When is septic better than a sewer line?

If you are not legally required to connect your property to a sewer line, a septic system can be cheaper to install and operate. They don’t require you to pay monthly sewer bills, and well-maintained units are more environmentally friendly.

Can you have a septic tank and city water?

Yes. California has no regulation preventing you from connecting your property to city water while also having a septic tank.