How Long Do Septic Tanks Last?

People who live in major cities may not realize that many homeowners depend on septic systems. According to the EPA, more than one-third of the homes in the southeastern states use these systems. Having lived in big cities in Southern California, I was surprised to learn that the house we bought in Lewes, Delaware came with a septic system. The first thing I thought was, ‘that’s cool, we are independent of the city.’ But we soon learned that the whole septic system was our responsibility. That wasn’t that cool. One thing I wanted to know is how long septic tanks last.

Generally speaking, a new septic tank made out of quality concrete or plastic can last over 40 years. Septic tanks made out of steel last on average from 15 to 20 years. While the type of material a septic tank is made of is a critical factor in determining its life span, other factors are also important, including the quality of the soil, what is flushed into the tank, and the amount of water usage.

Continue reading to learn how long septic tanks last and recommended maintenance.

How Long Do Septic Tanks Last?

The life expectancy of septic tanks depends mainly on the type and quality of the materials used to manufacture them. There are three main septic tank materials used to make septic tanks: steel, concrete, and plastic or fiberglass. The table below shows the potential life expectancy of these septic tanks.

STEEL15-20 yearsSteel will end up rusting and malfunctioning.
CONCRETE40+ yearsLow quality concrete and acidic soils may lower life expectancy.
PLASTIC40+ yearsLow quality mechanical components may lower life expectancy.

But even if you start with the best quality material, other important factors affect the life span of your septic tank. Most of these factors also affect the overall life span of your septic system.

Septic System Inspection

The EPA recommends that the average household septic system be inspected every 3 years. And once a year for systems with electrical float switches, pumps, or mechanical components.

Pumping Frequency

The tank naturally develops beneficial bacteria that help decompose some of the solids inside. But over time, the solids will accumulate because the bacteria alone can’t disintegrate all the solids. This is why it is very important to pump your septic tank periodically —typically every 3 to 5 years.

Water Usage

When your septic receives a lot of water in a short period of time, it can force wastewater out before the bacteria completes the breakdown of the organic waste. This can cause the solids to get washed into the drain field, which can tax the system. This can happen when:

  • Several consecutive loads of laundry are done back to back
  • A toilet’s water reservoir has a leak which introduces clean water directly into the system
  • Several showers or baths are taken back to back

Materials Flushed Down the Septic Tank

There are a number of everyday items that can damage your septic system and should not go into your septic tank, including:

  • Kitty litter
  • Tampons
  • Hygienic pads
  • Cotton pads
  • Cotton swabs
  • Any type of fabric
  • Earplugs
  • Cigarette butts
  • Toothpicks
  • Condoms
  • Dryer sheets
  • Dental floss
  • Disposable diapers
  • Wet wipes
  • Medications
  • Dirt

You may be surprised to learn that septic tanks, especially old ones, can cause a sinkhole.

Septic System Piping and Drain Field Life Span

Of course, you can have a good quality septic tank maintained correctly and still have your septic system fail. That’s because there are two other major components of the septic system to consider: the piping and the drain field.

The life span of a septic system piping depends on factors such as proper installation, invasive roots that may clog the pipes, groundwater flooding, or simple human interaction by running vehicles over the pipes.

The life span of a drain field depends mostly on the type of installation and how well the installation was executed. According to the EPA, the following types of drain fields exist:

  • Conventional
  • Chamber
  • Drip distribution
  • Aerobic Treatment
  • Mound (The one we have)
  • Recirculating Sand Filter
  • Evapotranspiration 
  • Constructed Wetland
  • Cluster / Community

And as mentioned above, the soil conditions (clay, rock, or sand) and maintenance frequency will also affect the life span of the overall septic system.

Signs of a Failing Septic System

When your septic system is at the end of its life, there are signs that will let you know. You should have them checked out right away, as you may be able to perform maintenance or make repairs rather than replacing the entire system.

These are some of the signs that could indicate that your septic tank is failing:

  • Water and sewage is backing up into the home from toilets, sinks, and drains
  • Sinks, bathtubs, and showers are draining slowly
  • You have standing water near the septic tank
  • You hear gurgling in the plumbing system
  • Bad smells are coming from around the septic tank
  • The grass around your septic tank is bright green and spongy
  • You find algae blooming in lakes and ponds nearby

Final Words

Septic tanks usually last between fifteen and over forty years, depending on the type of building material, but many factors play a role in the actual lifespan. It is important to maintain your septic, have it pumped at least every two years, and pay attention to any signs that it is having an issue.

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