When it comes to building reliable sewer systems and storm drains, the design of a manhole top is more important than many realize. Choosing between a flat top manhole and a cone top manhole affects everything from load capacity to access, safety, and long-term durability. For contractors and municipalities across the United States, suppliers like Eagle Concrete provide both custom and standard sizes in precast concrete so each project gets the right fit.
What Is a Cone Top Manhole?
A cone top manhole is designed with a tapered manhole cone that reduces the larger barrel diameter to a smaller opening. This smaller opening is typically sealed with manhole covers, providing a controlled access point for maintenance and inspection.
Cone tops come in two main styles:
- Concentric cone: The opening is centered over the barrel.
- Eccentric cone: The opening is offset, allowing easier ladder or step entry.
Cone tops are often used in sanitary manholes, storm manholes, and other locations where a compact surface opening is needed. Contractors appreciate their ability to withstand heavy traffic loads in parking lots and roadways.
What Is a Flat Top Manhole?
In contrast, a flat top manhole is built with a reinforced slab that leaves a broad or rectangular opening. Flat tops are often used with box inlets, stormwater catch basins, or precast concrete inlets, where surface water needs to enter the system directly through a grate.
Flat tops make it easier to integrate inlet risers, catch basin risers, or concrete manhole risers, adjusting elevation to meet grade. They’re frequently paired with catch basins in parking lots and roadway systems, where water needs to be captured quickly and efficiently.
Structural Integrity and Materials
Both flat and cone tops are typically manufactured from precast concrete. At Eagle Concrete, each product is designed with customizable sectional design to suit the project’s needs. Using riser sections and concrete knockout boxes, contractors can achieve proper elevation and make space for pipe connections of varying pipe sizes.
Protective measures such as bituminous coating or chemical resistant finishes can be added to extend the life of both sanitary sewer manholes and storm sewer manholes. This is especially important in projects tied to a treatment plant or industrial sewer line where corrosive conditions are present.
Applications of Cone Tops
Cone top manholes are ideal when:
- A smaller surface opening is required for a sanitary manhole or storm manhole.
- Projects involve heavy vehicle loads, such as in parking lots.
- Access for inspection crews needs to be controlled for safety.
- Drop manholes are required to manage changes in elevation.
Because the cone design narrows the opening, it provides additional structural strength, making it a standard choice in many roadway and municipal systems.
Applications of Flat Tops
Flat tops are used in situations where broad surface entry is necessary, such as:
- Stormwater catch basins designed to handle high volumes of surface runoff.
- Box inlets and curb inlet frames where water flows directly from the roadway.
- Precast concrete inlets placed in parking lots and commercial drainage systems.
- Projects needing multiple locations to accommodate different pipe entries and outlet configurations.
Flat tops often feature grated inlets and inlet risers that allow easy flow of surface water while keeping debris out of the system.
Custom vs Standard Designs
Not all projects can be built with standard components. Eagle Concrete specializes in both custom and standard sizes for precast manholes, inlets, and basins. For example, a contractor may need a standard precast manhole for a subdivision sewer system but require a custom catch basin riser for a roadway drainage system.
With a customizable sectional design, Eagle can tailor the layout to fit specific outlet pipes, pipe connections, or even unusual site constraints like confined spaces. This approach eliminates costly field modifications and ensures long-term system performance.
Service and Supply Advantages
Unlike many precast suppliers, Eagle operates from multiple locations to accommodate customer needs across Pennsylvania and beyond. By offering both ready-to-ship products and tailored solutions, Eagle reduces lead times. Orders are typically processed within standard business days, and contractors can pick up your order directly or arrange delivery.
Because Eagle is a precast concrete Pennsylvania leader, contractors also benefit from reliable logistics, strong product knowledge, and expert support. And as with all orders, customers are provided with clear communication on general terms so they know exactly what to expect.
Why the Choice Matters
The choice between a flat top and a cone top isn’t just about shape — it’s about system performance. Cone tops work best for sanitary sewer manholes and traffic-heavy areas, while flat tops are suited for catch basins, precast drainage inlets, and large-scale stormwater catch basins.
By pairing the right top with the right pipe size, pipe connections, and structural supports, contractors can ensure compliance, reliability, and longevity. With Eagle’s custom solutions, there’s no need to compromise — every project gets exactly what it requires.
Conclusion
Whether you need a cone top sanitary manhole for a sewer line, or a flat top stormwater catch basin for a parking lot, Eagle Concrete delivers solutions designed to last. With precast concrete manholes, box inlets, catch basins, and inlet risers, every product is built with structural integrity in mind.
By offering both custom and standard sizes, protective finishes like bituminous coating, and flexible options for pipe connections and outlet pipes, Eagle ensures each manhole or inlet structure is tailored to meet real-world demands. With precast concrete solutions manufactured in Pennsylvania and supplied across the United States, Eagle Concrete continues to set the benchmark for quality, reliability, and long-term performance.