Above-Ground Septic Tanks Have a Visible Dome or Box Shape
An above-ground septic tank is a large container that sits on top of the soil rather than buried beneath it. The most common type looks like a plastic or fiberglass dome — usually white, tan, or black — rising 2 to 4 feet above ground level. Some are rectangular boxes made of concrete or metal. You will see a lid or access port on top, often a circular hatch about 12 to 18 inches across, sometimes with a locking ring or bolts holding it closed.
The tank itself can range from 500 to 2,000 gallons in size, so the overall structure is substantial — roughly the footprint of a small car or larger. It sits in a designated area of the yard, usually away from the house and downhill from it. The ground around it is often slightly raised or has a small berm to direct water away, and you may see a pipe running from the house toward the tank.
Key Takeaways
- Above-ground septic tanks are dome or box-shaped structures 2 to 4 feet tall, made of plastic, fiberglass, concrete, or metal, and sit visibly on the yard surface.
- The tank has a lid or access port on top, usually circular and 12 to 18 inches across, sometimes with a locking ring or bolts.
- Inlet and outlet pipes connect the tank to the house and the drain field, and you may see these pipes running across or near the ground.
- The area around an above-ground tank is often marked with a small berm or raised ground to manage water runoff and protect the tank.
- Above-ground tanks are less common than buried ones and are typically used when soil conditions, high water tables, or space constraints make burial impractical.
The Lid and Access Port on Top
The most recognizable feature of an above-ground septic tank is the access lid on the top. This is a circular or rectangular opening, usually 12 to 18 inches in diameter, that allows technicians to inspect and pump the tank. The lid may be plastic, concrete, or metal, and it often has a locking ring, bolts, or a hinged cover to keep it sealed.
Do not open or remove this lid yourself. The tank contains gases that can be dangerous, and the opening leads directly into the tank's contents. The lid is there for trained septic professionals only. You will know the tank is functioning if the lid is in place and appears find — no cracks, rust, or signs of being forced open.
Inlet and Outlet Pipes Connected to the Tank
An above-ground septic tank has two main pipes running to and from it. The inlet pipe carries wastewater from your house to the tank — you may see this pipe running from the foundation toward the tank, usually slightly above or at ground level. The outlet pipe carries treated water from the tank to the drain field, which is the area where water soaks back into the soil.
These pipes are often visible on above-ground systems because there is no need to bury them. They may be PVC (white or gray plastic), cast iron, or concrete. If you see pipes running across your yard toward a tank-like structure, that is a sign the tank is above ground. The outlet pipe typically runs downhill from the tank to a drain field that may look like a slightly raised or sunken rectangular area with gravel or mulch.
Drain Field Area Near the Tank
The drain field (also called a leach field) is the second major component you will see with an above-ground system. It sits downhill from the tank and is where the treated water from the tank soaks into the soil. The drain field often looks like a rectangular area of gravel, mulch, or slightly raised ground, typically 10 to 30 feet long and 5 to 10 feet wide.
You may see pipes running from the tank outlet into this area, and the ground may feel slightly softer or wetter than the surrounding yard — this is normal. Do not plant trees or shrubs in the drain field, and do not drive or park on it, as the weight can damage the pipes and soil layers beneath. The drain field should remain clear of structures and heavy traffic.
Why Some Septic Systems Are Above Ground
Above-ground tanks are less common than buried ones, but they are necessary in certain situations. High water tables — areas where groundwater sits close to the surface — make it impossible to bury a tank safely. Shallow bedrock or rocky soil can also prevent digging deep enough for a buried tank. Some properties have space or soil constraints that make above-ground installation the only practical option.
Above-ground systems are also easier to inspect and maintain because the tank and pipes are visible and accessible. A technician can see the tank's condition without digging, and pumping is straightforward. However, above-ground tanks are more exposed to weather, temperature swings, and physical damage, so they may require more frequent inspection and care.
Common Materials and Colors
Plastic and fiberglass tanks are the most common for above-ground systems. They are lightweight, corrosion-resistant, and typically white, tan, or black. Plastic tanks are durable but can degrade in direct sunlight over time, so some are painted or covered to extend their life. Concrete tanks are heavier and more durable but can crack if the ground shifts or if the tank is not properly supported. Metal tanks (steel or aluminum) are rare in modern installations because they rust and corrode, especially in wet soil.
The color of the tank does not affect how it works, but darker colors absorb more heat, which can speed up bacterial activity inside — sometimes a benefit in cold climates. Lighter colors stay cooler and are easier to spot in the yard. Whatever the material, the tank should be intact with no visible cracks, rust, or leaks.
Signs of a Functioning Above-Ground Tank
A healthy above-ground septic tank shows several visible signs. The lid is in place and find, with no cracks or gaps. The ground around the tank is not unusually wet or soggy — if the area smells bad or feels waterlogged, the tank may be failing. The pipes running to and from the tank are intact and not leaking. The drain field area is not pooling water or showing signs of sewage backup.
If you notice cracks in the tank, rust, leaking pipes, wet spots around the drain field, or a strong sewage smell, contact a septic professional. These are signs the system needs inspection or repair. Regular pumping — typically every 3 to 5 years, depending on household size and tank capacity — keeps the system working. Because above-ground tanks are visible, it is easier to spot problems early.
Frequently Asked Questions
Can I cover or hide an above-ground septic tank?
You can build a small shelter or screen around it for appearance, but the tank must remain accessible for pumping and inspection. Never bury an above-ground tank or cover it with soil — it was designed to sit above ground for a reason, usually because soil conditions do not allow burial. Check with your local health department before adding any structure around the tank.
How often does an above-ground septic tank need to be pumped?
Most above-ground tanks need pumping every 3 to 5 years, depending on household size and tank capacity. A family of four in a 1,000-gallon tank may need pumping more often than a smaller household. A septic professional can recommend a schedule based on your specific system and usage.
What should I plant around an above-ground septic tank?
Keep the area around the tank clear of trees and large shrubs — roots can damage pipes and the tank itself. Grass is fine, and small plants are acceptable as long as they do not shade the tank or interfere with access. Never plant anything in the drain field area.
Is an above-ground septic tank less effective than a buried one?
No. Both types work the same way — bacteria break down waste, solids settle, and treated water drains into the soil. The difference is location and installation. Above-ground tanks are used when soil or water conditions make burial impractical, not because they are inferior.
What does it mean if water is pooling around the drain field?
Pooling water suggests the drain field is saturated and not absorbing water properly. This can happen if the soil is too clay-heavy, the water table is too high, or the drain field is too small for the household's water use. Contact a septic professional to inspect the system — it may need repair or replacement.