How Long Do Septic Tanks Last?

If you’ve recently bought a home with a septic tank, you’re probably wondering how long do septic systems last, mostly because they can be big-ticket purchases.

Well, the answer to how long do septic systems last depends on several factors such as construction material, soil acidity, water table and proper maintenance practices.

If you’re thinking of purchasing a house, a home inspector can usually inspect the tank and pipes and estimate the age, or a septic professional if you already have a septic system.

The average lifespan of a septic system is between 15 and 40 years, assuming it was properly designed and properly installed by a qualified plumbing professional and according to the proper building codes.

Why Do Septic Systems Fail?

Overloading the septic system

One of the biggest reasons for a short septic system lifespan is the overloading of the system with more wastewater than it can handle. Each septic system is designed for a specific wastewater flow rate, which is generally 110 gallons per bedroom per day.

In the event this flow rate is exceeded, the wastewater is forced out of the septic tank, and this leakage of wastewater can end up in your yard or in your house.

Clogged cast-iron pipes or other pipes from the house to the septic tank

If you have a clogged pipe with organic waste from the house to the tank, the drain will drain very slowly or, in worse cases, will stop draining completely. In most cases, this is an easy issue for people to fix with a snake to get it unclogged.

Drainfield has failed

A septic drain field is an important component of a septic system, and is a shallow, covered, excavation made in unsaturated soil. If the drainfield is saturated with water, sewage may backup into your home and create backups in toilets and sinks.

Key Signs of Septic System Failure

There are several signs of septic tank failure and when your septic tank isn’t functioning properly, most notably:

  • Gurgling sounds in the plumbing system
  • Slow draining in bathrooms, showers and sinks
  • Water and sewage such as human waste from sinks, drain pipes and toilets backing up into your home
  • Bad odors around the drainfield or septic tank
  • Standing water or damp spots near the tank

Factors for Lifespan Projection of Septic Tank

Construction Material

The national lifespan average of a septic tank depends on what construction material and the quality of material the septic tank is made from. There are several types of construction material used in the making of a septic tank, but the two most common are steel and concrete tanks.

Steel Tanks – 15-Year Lifespan

Even though steel is one of the most solid materials in the market that is used for several applications, it only offers a short lifespan of 15 years when used in the construction of septic tanks.

A steel tank is prone to rust, but you can typically see an increase in lifespan if the rust is caught early enough, because irreparable damage can result in exorbitant costs to fix.

So, if your steel septic tank is over 10 years old, you should have it inspected for physical damage by a professional plumber asap.

Concrete Tank – 40-Year Lifespan

The average cost of a concrete septic tank is much higher than a steel septic tank, but, on a brighter note, it offers a much longer service life than plastic septic tanks and steel septic tanks.

A concrete septic tank offers a minimum 20-30 year service life, and much more in most cases if maintained properly.

As long as the tank was built of high quality concrete and the pipes don’t clog or there are no corroded pipes, there aren’t very many external factors that will decrease the lifespan of concrete septic tanks.

However, just like steel septic tanks, you should have concrete septic tanks periodically inspected to ensure there are no cracks as a result of ground shifting or settlement.

Drainfield – 50 Year Lifespan

The drain field, aka leach field, is a bunch of pipes that extend from the tank and disperse the waste. A damaged drainfield can spurt waste and sewage into your yard, which can be a major health issue for people and pets.

The series of pipes in the drain field are usually made from steel, PVC plastic or cast iron, which are known to last up to 50 years if installed and maintained properly.

Soil Type

The type of soil is another factor that can affect the longevity of your septic system. If your drainfield is stuffed in hard, clay-like soil, it will make it hard for the waste it carries to disperse into the soil, resulting in clogs that back up your septic tank.

When installing your septic tank, it’s a good idea to use non-acidic soil, because acidic soil can eventually corrode plastic, steel and cast-iron pipes.

Highly acidic soil is a big concern when it comes to the service life of your septic tank, which is why it’s important to have your soil tested to determine the level of acidity.

How to Tell if a Septic Tank Needs to be Replaced?

There are several tell-tale signs that your septic tank needs replacement such as:

  1. Grass is always greener – Who doesn’t like lush green grass, but it could be indicative of an issue if the grass is growing greener or faster in one area.
  2. Soggy leach field – When your septic tank is first installed, it is placed in an area known as a leach field. If the leach field is soggy or flooded, it may be time for septic tank replacement.
  3. Stinky yard – If your yard smells like rotten eggs or sulfur, it’s a good sign that raw sewage has leaked from the septic tank or the pipes.
  4. Toilet issues – If you have a clogged toilet, and you use a plunger to try and unclog it without any success, your septic tank is probably full. You will have to get your septic tank pumped and if this doesn’t work, you should call a plumbing professional right away.
  5. Well water contamination – If you test your well water or drinking water, and the results show that bacteria, nitrates or other contaminants, you may need to buy a new septic system.

How Can I Make My Septic Tank Last Longer?  

Inspecting your system regularly is one of the best ways to make your septic tank last longer. If you aren’t aware on how to properly inspect your system to see if it’s working properly, it’s recommended that you call professional help.

Next, it’s a good practice to pump your septic tank as needed. The frequency of pumping your septic tank depends on the number of people using it, where the higher the number, the more frequently you will have to pump the septic tank.

As a rule of thumb, you should pump your septic tank every three to five years. You should also have your septic tank inspected by a professional at least every three years, and refrain from flushing solid objects.

Always use water efficiently, because the more wastewater produced by your home, the more load you put on your entire septic system.

How Much Do Septic Tanks Cost to Replace?

The cost of installing a new septic tank is roughly $4000. The price of septic tanks ranges between $1,500 to $5,000 for a typical 1,250-gallon tank, which is an ideal size for a 3-bedroom home. This cost includes the cost of the septic tank, and depends on the type of tank you buy.

Routine Maintenance and Inspections – Regular Maintenance Goes a Long Way

As mentioned earlier, you should have your conventional septic system and drain field inspected every three years or so. For a well-maintained septic tank, you should have all the other parts inspected every year.

People often wonder how long can a septic system sit unused for, and the answer is for a while. An inactive septic system will have less wastewater and require less maintenance.

Final Thoughts On How Long Do Septic Tanks Last

As mentioned previously, a septic tank should last anywhere between 15 and 40 years, but there are so many variables that it is impossible to give a “one size fits all” answer.

If you are purchasing a property where a septic system is installed, and are not sure of the age or condition of the septic tank, then it would be advisable to seek a professional opinion regarding the age and condition of the septic system.