Cracked Concrete Septic Tanks: Causes, Symptoms, And Solutions

Plastic and fiberglass septic tanks have their positive aspects, but many homeowners and businesses that rely on septic systems swear by concrete septic tanks. Concrete tanks are cost-effective, reliable, and most importantly, incredibly durable. Many concrete tanks remain in use for decades.

Unfortunately, while concrete septic tanks are very tough, occasionally a concrete tank will become cracked. Cracks in concrete septic tanks can cause serious problems and must be inspected and repaired as soon as possible.

What Causes Cracks In Concrete Septic Tanks? 

A number of problems can cause cracking in concrete septic tanks:

Tree Roots

If there are any trees growing near your septic tanks, their roots may grow toward the tank to try and reach the nutrient-rich sewage within. If these roots grow into gaps around the tank's lid, outlet pipes, or inlet lines, the force created by the growing roots can crack the surrounding concrete.

Ground Movement

If the soil surrounding your septic tanks is shifted or disturbed, the immense pressure created by the moving earth can crack the toughest concrete septic tanks. Ground tremors, subsidence, and expanding clay soils can all crack your tank.

Heavy Vehicles

The weight of heavy vehicles passing overhead can cause catastrophic damage to septic tanks. Most concrete tanks have very high load-bearing strength, so this problem is usually caused by very heavy commercial, agricultural, or construction vehicles.


Concrete septic tanks last for a long time, but eventually, the concrete will degrade, weaken, and become vulnerable to cracking. Tanks with metal reinforcements can also become cracked if the metal starts to corrode.

How Can You Tell If Your Concrete Septic Tank Is Cracked?

If your concrete tank is cracked, it will leak in both directions: groundwater and soil will leak into the tank, and untreated sewage will leak out of the tank. This can cause a number of serious problems.

Water and debris leaking into the tank alters the chemistry of the tank's contents and can kill the beneficial bacteria that break down the sewage inside your tank. If sewage stops breaking down properly, the tank may fill up more quickly, or start to overflow. This can cause bathtubs, sinks, and toilets to drain slowly, or not at all. In severe cases, sewage may start backing up into your building

Sewage leaking out of a cracked tank can cause widespread contamination and may be a serious health risk. Check for foul smells and wet, saturated soil above and around your tank. You should also be concerned if the grass growing over your tank is unusually lush and green, as it may be nourished by sewage leaking from a cracked tank.

What Should You Do If Your Septic Tank Is Cracked?

If you suspect your concrete septic tank is cracked, you should call in a professional septic tank repair service as soon as possible. These services will inspect the interior and exterior of your tank to check for cracks and other signs of damage. Specialized cameras can be inserted into your tank to check its interior, but it may be necessary to partially excavate the tank to check for exterior damage.

If your service finds any significant cracks, they will determine whether repairs are possible. In many cases, cracked concrete tanks can be repaired using strong, commercial-grade concrete fillers and sealants. If your concrete tank is very badly damaged or is too old to be effectively repaired, it may need to be replaced. 

Contact a local septic tank repair service to learn more.