One of those things that people think goes on forever and they are surprised when it doesn’t, is septic tanks. A buried tank is out of sight and out of mind, and so it seems like it is permanent. For a long time, it is. However, all tanks do have a lifespan and when it becomes more cost effective to replace than repair, it is important to understand that point before failure happens, and not after.
There isn’t a specific number of years that a septic tank will last. This may vary depending on the material of the tank, the maintenance of the tank, the condition of the surrounding soil, and the intensity of tank usage. Here’s a realistic breakdown.
Lifespan by Tank Material
The material your tank is made of is the biggest factor in how long it will last.
Concrete tanks: The majority of tanks throughout the City of Kelowna and the rest of the Okanagan are concrete tanks. A well constructed concrete tank can be expected to last 40 years or longer if it is installed in reasonable soil. Some go longer. The problem about concrete is that it’s not immune to the chemistry of what it contains. Anaerobic bacteria that form hydrogen sulfide gas in the tank react with water in the tank and create sulfuric acid, which slowly eats away the inside of the concrete. A poorly maintained tank will deteriorate more quickly as the chemistry in an overloaded tank is more aggressive.
Steel Tank: The life span of steel tanks is much shorter. Most steel tanks installed decades ago are now at or past the end of their useful life. Steel is subject to corrosion and after a certain degree of corrosion the structural integrity of the tank is compromised. If your tank is steel and over 25-30 years, and hasn’t been assessed recently, consider having it evaluated as soon as possible.
Plastic and Fibberglass: Plastic and fibreglass tanks are highly corrosion resistant and do not suffer from the degradation that can occur in concrete and steel tanks. They are physically weak. They can be damaged by ground movement, root intrusion, or installation and in some soil conditions, they will move more than heavier tank types. If properly installed and maintained, they can last for 30-40 years.
What Shortens a Tank’s Lifespan
The manufacturer’s guaranteed lifespan is based on the assumption that the tank will be used and maintained in the manner for which it was designed. There are a number of factors that can cause deterioration beyond normal wear.
- Infrequent emptying. If a tank is not pumped regularly, sludge accumulates to the extent that it cannot be properly treated by the system. Excess load will create stress to both the tank and the drain field. A tank that is emptied every three to five years will last longer than a tank that goes 10 years between services.
- Putting the wrong materials into the drain. The use of wipes, sanitary products, grease, harsh chemicals and using too many garbage disposals all affect the bacterial balance inside the tank and can cause the corrosive chemistry that can damage concrete tanks over time to be accelerated.
- Tree roots. A septic tank is an easy target to attract roots due to moisture and nutrients. Root intrusion isn’t just the cause of leaks. This will enlarge existing weaknesses in the structure over time.
- Heavy surface loads. Heavy equipment and vehicles that are driven over or parked on the tank area will compact the soil and break the tank lid or the tank itself. It’s one of those things that doesn’t immediately cause obvious damage and turns into a structural problem years later.
- Poor original installation. The early issues that can arise with a tank are due to lack of suitable soil, improper tank depth, or improper tank bedding. If you are having repeat problems with a relatively young system, consider installation quality as a possible factor.
Signs the Tank Needs Replacing Rather Than Repairing
Not every septic problem means the tank needs to go. A blocked pipe, a failed baffle, or a straightforward maintenance issue can often be fixed without touching the tank itself. These are the signs that the tank specifically has reached the point where replacement is the more practical path.
Structural cracking: In some instances, a concrete tank can be repaired by sealing hairline cracks during a service call. If the tank has significant cracking that is compromising the structural integrity of the tank, especially near the inlet and outlet or if the cracks are recurring after repair, the tank is past the patching stage.
Persistent groundwater infiltration: If there is a continuous infiltration of groundwater through the cracks and/or broken joints, the system is handling a lot more water than it is supposed to. The tank is working harder than it is supposed to, the drain field is being overloaded and the problem will tend to get worse over time instead of better.
Sewage surfacing near the tank. Liquid waste appearing at ground level near the tank area means effluent is escaping somewhere it shouldn’t. This is both an environmental problem and a health one, and it almost always indicates a failure that repair alone won’t resolve permanently.
A tank that’s collapsed or severely deformed. This is the clear-cut case. A tank that has physically failed can’t be fixed with a patch. It needs to come out.
Age combined with repeated problems. A concrete tank at 40 or 45 years that keeps presenting different issues is telling you the same thing each time. When the cost and frequency of repairs starts to approach the cost of replacement, the economics of continued repair stop making sense.
What Happens During Tank Replacement
Knowing what the process involves takes some of the uncertainty out of it.
The old tank is excavated and removed. Before the new tank goes in, the soil around and beneath the installation site is assessed to make sure it can support the new system properly. A new tank, sized appropriately for the property and its usage, is installed and connected to the existing inlet and outlet pipe runs where those remain serviceable. The area is backfilled and the system is tested before the crew leaves.
Depending on the age of the system, a drain field assessment is usually part of the conversation at the same time. A tank that has been failing or overloading the drain field for an extended period may have caused drain field deterioration that needs to be addressed alongside the tank replacement. Replacing a tank while leaving a compromised drain field in place doesn’t fully resolve the system failure.
The Role of Regular Inspections
The best method to determine how well your tank is doing is to be sure to have it checked regularly, not only waiting for symptoms to occur. OK Eco Pump suggests that the system must be inspected every 1-3 years depending on home size, usage, and the age of the system.
An inspection taken at the proper time reveals the signs of deterioration before it becomes a problem. It also provides you with a service history that documents the service performed and is actually helpful when considering tank repair versus replacement, and when the question of the tank’s remaining serviceable life needs a real answer rather than a guess.
OK Eco Pump is a tank emptying, deep cleaning, inspection and full system assessment provider for the Okanagan region and the City of Kelowna. Please contact (250) 826-2325 or email tom@okecopump.com to arrange a visit.