Septic tanks are a type of onsite sewage facility. They are frequently used in rural areas that are not connected to a sewerage system. After 23 years in the septic tank servicing industry, I’ve found that most folks do not understand how their septic system works or how to properly take care of one.
Septic Tank Types and Design
Most septic tanks are made from either concrete, plastic, or fiberglass. In the past, some tanks were produced from steel. However, metal tanks have now been banned in many states. Steel tanks are prone to rusting, which leads to perforations and potential collapses. It can also make them difficult to remove.
Average LifeSpan of a Septic Tank
Plastic and fiberglass tanks will last virtually forever as long as they are installed with great care. Most of the failures we see are due to incorrect installation depth or how the area around the tank was backfilled. If they are buried too deep, the weight of the soil on top can cause the tank to become distorted and possibly crack. Each manufacturer has guidelines for tank installation depth. The ground is always moving, so backfilling around a tank with sand, gravel, or clean dirt will protect the tank long term. Conversely, using rocky soil to backfill around the tank can permit rocks to rub a hole in or puncture the tank over time.
The life span of concrete tanks will depend on the manufacturer and the year they were built. Different states have varied rules on tank production. Tanks that were built prior to the 1980s will usually have a concrete or cast iron pipe baffle assembly. The cast iron usually closes up as it degrades, similar to a clogged artery, thus slowing or stopping flow through them.
The concrete baffles of this era usually decay; either the top erodes away or the whole baffle falls off into the tank, allowing solids to float across the top and right on out to the lateral field. In the 1980s and 1990s, to correct the problems with the concrete and cast iron baffles, tanks often had a plastic baffle fastened to the walls of the tank. They work well until the steel fasteners used to attach them to the walls decay and break off, which allows the baffle to come loose and fall into the tank. Concrete tanks built from the mid to late 1990s through today are built with PVC pipe baffles. They will last forever as will plastic and fiberglass tanks.
Factors Affecting Septic Tank Lifespan
As with most things in this world, the human is the greatest threat to a tank’s lifespan. When a tank is installed properly and maintained appropriately, it will generally last multiple lifetimes as long as it is protected from human mistakes or natural catastrophes. Examples of natural catastrophes would be when a tree falls on top of the tank or a severe lightning strike (which I’ve only seen once in my life).
In regions where earthquakes occur, tanks can crack or break. When a heavy tree falls over a tank lid, it can crack or break the lid. Human mistakes, such as people who decide to drive or park heavy objects like equipment or vehicles above the top of the tank, can cause the top to be cracked or caved in despite being buried. I’ve also seen people build room additions or decks over part or all of the tank. At best, this makes it hard to maintain the tank. At worst, the weight on the tank will be too heavy and will cave in the top.
It’s also important to know about what kinds of trees are planted in the area where your septic system is located. Certain kinds of tree are more aggressive when seeking water supplies and their roots can break pipes and grow through seams or cracks and, over time, can stop flow or even fill up the entire tank with roots. Check out our BBBseptic.com blog for more on this topic.
Signs of an Aging Septic Tank
The outside of tanks will often show cracks, breaks, or punctures from rocks or buried sharp objects, although you won’t typically see these unless you dig and uncover the tank. Signs of aging will often be detected from looking inside the tank. Water level is the key indicator. If the level is too high, it can indicate that there is a problem with the outgoing part of the tank or with the distribution box or lateral line system. If the level liquid level in the tank is too low, it will usually be due to a crack or puncture in the tank sides or bottom.
On older tanks, where the baffles are not PVC, you might see that the plastic baffles are starting to fall or have completely come off. The concrete styles may also have eroded or fallen off. Both of these types of deterioration can be addressed by a professional installation of a new PVC baffle assembly. You might see some erosion in concrete tanks on the inside at the water line, or around where the pipes come in and out of the tank. This is usually superficial and should not be cause for concern. Having a professional service your system periodically will allow you to catch most problems before they become fatal.
Proper Septic Tank Maintenance
Throughout the USA, states have different rules and regulations on how septic systems are to be installed and maintained. This is influenced greatly by the soil types in different regions, from the sandy soil along the gulf to the black dirt in the north, and the wet conditions of the lowlands, or dry conditions of the southwest. There are some simple guidelines that fit for most conditions, such as pumping your tank out periodically and remembering not to put any more solid materials or trash down your drains than absolutely necessary.
In Arkansas, the state requires systems to be designed with a 3-5 year pump out schedule in mind. This means that normal usage will create a solid build up which will need to be pumped out to ensure they don’t end up in the absorption area and damage the soils ability to treat the water as it re-enters the natural water tables.
You also need to remember that your system is an ecosystem that needs to be balanced. Someone using a septic where the water supply is a spring or well should make it easier for the natural bacteria to grow. Where public water is used, the chlorine in the public water system will also kill or stunt the bacteria in your septic system.
It’s also important to note that the use of antibacterial soaps, bleach, detergents, and cleaners will stunt or prohibit the growth of bacteria, as will some pharmaceuticals and medical treatments like chemotherapy. Some septic system bacteria treatments can overcome these conditions.BBB Septic and Portable Toilets
Overall, I believe that septic systems are one of the best ways of treating wastewater. When properly maintained, they will last indefinitely and using the earth’s natural processes, they are effective without using up any other natural resources. Even including the cost of good maintenance, septic systems are also much less expensive to operate than paying a monthly sewer bill.