How Many Years Does A Septic System Last?

Stacy Randall
by Stacy Randall

If you’ve just moved into a new home in a rural or suburban area, chances are you have a septic system. But don’t worry! A septic system shouldn’t be a deal-breaker, though you might be wondering how long it will last.

A septic system can last for 15-40 years depending on installation, maintenance, and usage. Steel septic systems only last for 15-20 years, and plastic tanks can last for 30-40 years. Concrete septic systems are the strongest and can last more than 40 years.

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How Long Does a Septic System Last?

It is true that with the proper maintenance and care, a septic system will last you many years. However, though these systems are designed to last, a septic tank that is installed underground will deteriorate eventually.

The average lifespan of a septic system depends on a number of factors including the material it is made of, how well it was installed, its’ workload, and how well it’s maintained. Though, you can typically expect your septic system to last between 15 and 40 years.

Septic Tank Materials

Septic tanks are most commonly made of steel, plastic, or concrete. Each material has its pros and cons that contribute to how long the septic system is going to last before needing a repair or replacement.

1. Steel

A steel septic tank will inevitably rust over time. How quickly the tank will rust is affected by soil acidity and the steel septic tank’s quality. The worse the quality of steel, the faster your septic tank will rust.

Because of its habit of rusting, steel septic tanks tend only to last fifteen to twenty years. Rusting can get so bad that tank bottoms disappear entirely as the rust eats it away.

To ensure your steel septic tank lasts as long as possible, you should have it inspected often. A professional can catch rust and other issues before they become more significant problems.

2. Plastic

Plastic septic tanks are cheaper and easier to install than other septic tanks. It is also possible to install a plastic septic tank in a wider variety of places than other tanks.

Plastic septic tanks are crack-resistant due to the flexibility of the material. They are also immune to corrosion, meaning they won’t rust like steel options. Because of this, plastic septic tanks can last thirty to forty years if well-maintained.

However, because plastic is less sturdy than other septic tank material alternatives, it can get crushed more easily. If vehicles drive over where your tank is buried, the pressure will likely crush a plastic septic tank. Though crack-resistant, plastic septic tanks are more susceptible to damage than sturdier materials like steel and concrete.

3. Concrete

Concrete has the longest lifespan of any septic tank material. If well-maintained, concrete tanks can last anywhere from forty years to indefinitely. Concrete septic tanks are very durable because concrete is so sturdy.

Concrete septic tanks also won’t be affected by changes in the environment. These changes include growing tree roots, changing soil conditions, or vehicles driving over the area where the tank is buried. You also won’t need to perform as much maintenance on concrete septic tanks as on their counterparts.

However, concrete is more vulnerable to corrosion and susceptible to cracks than plastic tanks. Corrosion is more likely to occur if you have highly acidic groundwater in your soil.

If your concrete septic tank is well-maintained, you can avoid cracks and corrosion. If your tank is ill-maintained, cracks can get out of hand and cause complicated septic tank repairs.

Why Do Septic Systems Fail?

The most common cause of septic system failure is poor maintenance. Though, they can also fail as a result of inappropriate design, improper installation, overloading the system with more water it can take, or even physical damage.

Septic System Maintenance

No matter the material your septic system is made from, it is only as good as its maintenance. If you take poor care of your septic system, this drastically reduces its lifespan. The following are just a few ways to maintain your septic system properly, so it works for years to come:

  • Have your septic system inspected regularly. It is recommended that you schedule a septic system inspection every three years. This allows a professional to diagnose any issues before they become major problems. 
  • Have your septic system pumped regularly. It is recommended that your septic system be pumped every three to five years. However, if you create a considerable amount of wastewater, you may want to have your system pumped more frequently. 

Frequent pumping prevents major clogs in your pipes and clears the excess waste from your tank. Without regular pumpings, your septic system cannot function as it should. Wastewater can then back up into your drains, causing a foul odor and general unpleasantness.

  • Do your best to send only water and waste down your drains. Your septic tank is not equipped to handle waste like large food scraps or coffee grounds from your kitchen. Toss these into your trashcan. 

In your bathroom, dispose of sanitary napkins, tampons, and diapers in the trash, not down the toilet. Never send chemicals or grease down your drains. Large deposits of non-biodegradable waste can create major clogs in your septic system.

  • Avoid parking on your drainfield. Your drainfield is an essential part of your septic system, filtering wastewater. Parking and driving over your drainfield can cause the soil to shift, and the pressure can crush your septic tank. This is a surefire way to end your septic tank’s life prematurely.

Quality of Your Septic System’s Installation

A septic system is only as good as its installation. Inadequate installation of your septic system can lead to many problems that will drastically reduce its lifespan.

Here are installation issues that can cause problems for your system:

  • Your septic system was installed in impermeable soil. Your septic system’s drainfield needs to be able to filter wastewater into the soil for absorption. If your system is located in hard, clay-like soil, wastewater cannot be adequately absorbed. 
  • Your septic system was installed in overly-saturated soil. This won’t allow the proper absorption of wastewater. If soil is too wet to begin with, the wastewater will begin to collect on top of the drainfield. This can lead to foul odors, sewage backup in your drains, and groundwater contamination.
  • Your septic system was constructed poorly. If this is the case, you will likely have problems from the get-go. Poor construction means your septic tank is more susceptible to cracking, corrosion, and other issues during its lifespan. 
  • Your septic system is an inadequate size for your home. The size of a septic system is based on the number of people living in the house. If a system is too small, it won’t handle the wastewater your household produces. This will cause your system to peter out early. 
  • Your soil is too thin. If the soil above your septic system is too thin, it can’t treat the wastewater properly. This poorly treated wastewater then contaminates the groundwater around your home.

Septic System Workload

If you are producing an excess of wastewater, you may be overworking your septic system. Producing more wastewater than your septic system is designed to handle can cause it to deteriorate quickly.

You can counteract excessive water usage by doing the following:

  • Conserve water. Only do full loads of laundry or dishes. Don’t leave the water running while brushing your teeth. 
  • Install high-efficiency toilets. More efficient toilets save water, especially if there are many people in your home using the bathroom. High-efficiency toilets use about 1.6-gallons or less during each flush. This is a big difference compared to the 3.5 to 5-gallons-per-flush for older toilets. 
  • Install high-efficiency showerheads and faucet aerators. These items restrict the water flow on your appliances, which in turn saves water. 

Physical Damage

Building, paving, or driving over a septic system can cause damage or potentially render it irreparable. From repeated or even sporadic abuse, the pipes and/or tank of these system may shift or be crushed. The soil may also get compacted or ruts may be created, which exposes the system’s components and may also bring untreated sewage to the surface.

Paving over all or even a section of the drainfield can limit the airflow to the soil, while also preventing access for maintenance and repairs. Building over your drainfield can result in compaction or damage the linen because of the structure’s weight. Both paving and building over a septic tank will also prevent any necessary tank maintenance.

Tree roots are another possible way that your septic system can incur physical damage, clogging the drain lines and gravel in the trenches. The best way to prevent this from happening is to avoid planting trees or shrubs within 25 feet of the drainfield.

Signs of Septic System Failure

Although septic systems are designed to last you several decades, you should still keep a look out for problems, regardless of its age. Some of the signs of a malfunctioning septic system include:

  • Consistent puddles over your drainfield.
  • Sewage backing up into your toilets, sinks, or throughout your plumbing pipes.
  • Greener grass present above your drainfield.
  • Foul odor around the septic tank.

If you detect an issue with your septic system, you’ll want to reach out to a certified professional immediately. These problems need to be dealt with quickly. Replacing or repairing a septic system is not suitable as a DIY project.

Another common sign that a replacement for your septic system is in your future is simply based on its age. It’s very common for septic system to last 40 years. So, if you’ve recently bought a new home, it likely won’t need replacing. However, if your home is older, it’s possible that the septic system is nearing a half a century year old.

If you start to notice any of the other aforementioned signs, it may be time to start budgeting for a new system. That said, it’s in your best interest to determine the approximate age of your system, assuming you don’t already know it.

Related Questions

How much does it cost to repair a septic tank?

If you suspect something is wrong with your septic tank, it can cost anywhere from $500 to $2500 to repair your tank. Major problems may cost around $5,000 to fix. However, these repairs are necessary to increase the longevity of your septic system. 

How much does it cost to install a septic system?

A septic system can cost an average of $3,200 to $5,000 to purchase and install. Price per system varies on the size and location of installation. In some cases, replacing a damaged system can cost upward of $20,000.Plastic tanks are generally cheaper to buy and install. Concrete tanks can cost anywhere from $600 to $1000 without installation costs. 

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Wrapping Up

A septic system can last anywhere from fifteen to forty years, depending on materials, maintenance, quality of installation, and workload.

Your septic system can be made of steel, plastic, or concrete. Steel lasts fifteen to twenty years, while plastic lasts about thirty to forty years. Concrete systems last the longest, with a lifespan of forty years to a lifetime.

Proper maintenance and use will help to extend your septic system’s lifespan. Have it pumped and inspected regularly, and only send wastewater down drains. Also, avoid driving or parking on drainfields.

If your system was installed improperly, this could also shorten your system’s lifespan. Impermeable, overly-saturated, or too thin soil, poor construction, and inadequate system size will cause a problem.

Try your best not to create an excess of wastewater that can overwork your septic system. Conserve water and install high-efficiency toilets and showerheads. Following this advice can ensure your septic system has a long and happy life!

Stacy Randall
Stacy Randall

Stacy Randall is a wife, mother, and freelance writer from NOLA that has always had a love for DIY projects, home organization, and making spaces beautiful. Together with her husband, she has been spending the last several years lovingly renovating her grandparent's former home, making it their own and learning a lot about life along the way.

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