Updated October 2026. Repair methods from engineering and inspection references; costs and lifespans from the U.S. EPA.
Small cracks in a concrete septic tank can often be repaired by a septic professional, after the tank is pumped, using epoxy, hydraulic cement or polyurethane injection. Wide cracks, cracks in load-bearing walls, a sagging or collapsing tank, or a tank near the end of its life usually mean replacement. Do not try to repair a tank from inside it: septic tanks hold toxic gases, and entering one can be fatal.
Signs your septic tank is cracked
- Wet, soggy ground or sewage odor around the tank, especially when the drainfield area is dry
- The tank fills with water faster than usual, or the level drops after pumping (groundwater leaking in or effluent leaking out)
- Bright green grass in a patch over the tank
- Sinking soil or a depression over the tank
- Your pumper reports cracks, roots inside the tank or damaged baffles
InspectAPedia notes that cracks can let groundwater seep in or septic effluent seep out around the tank. Either one is a problem: groundwater floods the drainfield, and leaking effluent can reach wells.
What causes septic tanks to crack
- Heavy loads: vehicles, equipment or construction over the tank
- Age and corrosion from sewer gases attacking the concrete above the water line
- Tree roots forcing their way into joints
- Ground movement, freezing and settling
- Pumping a tank in very wet ground, which can let groundwater pressure crack or lift it
Repair or replace? How pros decide
| Situation | Likely fix |
|---|---|
| Fine cracks, tank otherwise sound | Repair: epoxy injection or sealant |
| Accessible surface cracks in walls or lids | Repair: hydraulic cement patch |
| Leaks below the water line | Repair: polyurethane foam injection |
| Cracks wider than about 1/8 inch or in load-bearing areas | Usually replace |
| Tank settling, sagging or collapsing | Replace |
| Tank at or past its expected life | Replace; repeated repairs can cost more |
Those criteria follow EVstudio’s guidance on septic tank cracks, which also stresses that repairs should be done by qualified professionals. Your local health department may also require replacement of a failed tank.
Think your septic tank is cracked?
A pump-out and inspection shows whether a crack can be sealed or the tank needs replacing. Talk to a local septic company about an inspection.
Calls are answered by a pay-per-call partner network that connects you with a local septic company. Calling is free; we may be paid for referrals.
How a cracked septic tank is repaired
- The tank is pumped empty and cleaned around the damaged area.
- The septic pro decides on the method based on the crack size and whether it is above or below the water line.
- The crack is sealed with epoxy, hydraulic cement or injected polyurethane foam. Some tanks get an internal liner instead.
- Baffles, lids and risers are checked and replaced if damaged.
Keep children, pets and yourself away from an open tank. A missing or cracked lid is a fall hazard; see how to replace a septic lid.
Cost to repair or replace a cracked septic tank
Crack repairs are priced by the job, so get a written quote after inspection. For replacement, the EPA puts repair or replacement of a conventional septic system at $5,000 to $15,000; replacing only the tank usually costs less than a full system. The EPA says a concrete tank may last 50 years or more, so an old tank with several cracks is often due for replacement anyway.
Quick answers
Can I fix a cracked septic tank myself?
Not safely. The repair needs the tank pumped and work close to or inside it, and septic gases can be deadly. Hire a septic professional.
Do plastic septic tanks crack?
They can, usually from heavy loads or shifting ground. Damaged plastic tanks are more often replaced than patched. See types of septic tanks.
Is a cracked septic tank an emergency?
It is urgent if sewage is surfacing, the tank is sinking or a lid is broken. Keep people away from the area and call a septic company.
Sources
- EVstudio, Repairing cracks in septic tanks
- InspectAPedia, Concrete septic tanks
- U.S. EPA, Why maintain your septic system