Catch Basins and Manholes

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Catch basins and manholes each use the same precast structures, but the structures are used for different purposes. A.J. Foss manufactures a complete line of custom catch basins and manholes to support all your needs for wastewater and stormwater systems.

Typically on catch basin a slotted or perforated metal grate is set on the top of it at ground level to allow water to enter into the structure.

On a manhole the top is closed, so you would use a solid cover on top of it, either 24" or 30" in diameter.

Catch Basins

A catch basin is a type of drainage inlet designed to collect excess rain and storm water runoff from roofs, sidewalks, parking lots, and paved streets.

A catch basin is a structure made of precast concrete with a sump* that allows solids, trash and debris to settle out to the bottom of the basin, below an outlet pipe that allows water to flow out of the structure. During a heavy rain storm, a catch basin and sump can become overwhelmed to the point of not enabling trash and debris to settle out. The high rate of water flow can cause the trash and debris to rapidly rise toward the outlet pipe, and since pipes are not typically fitted with hoods or trash-screens, any material that becomes suspended in the water near the outlet pipe can exit the structure through in the high rate of discharge flow.

We recommend using a hooded outlet cover that converts any sumped stormwater structure to reduce pollutants such as floatables and trash, as well as free oils, and sediment.

*Sump is the distance from the bottom of the structure to the bottom of the outlet pipe. A catch basin sump depth is typically 3 feet, and a manhole sump depth is typically 6 inches.

Advantages of Catch Basins:

  • Catch Basins & Manholes are H-20 Loading
  • Rubber Boots can be used
  • They ensure water-tight pipe-to-structure connections and quicken the installation time. (No need to wait for the hydraulic cement to dry before back-filling the structure)
  • Crafted with precast, high strength concrete
  • Easy and quick to install
  • Various sizes available, to address design parameters
  • A drop inlet catch basin is ready-for-installation. (While a typical catch basin is made to order, we stock blank pieces for which we use our advanced coring machine to core the required holes at the appropriate heights and elevations.

Catch Basin Component Sizes

  • Flat top cover sizes range from 1 to 4 feet
  • Riser sizes range from 1 to 4 feet
  • Base sizes range from 2 to 5.5 feet

4' Catch Basin Components Diagram

5' Catch Basin Components Diagram

Catch basins are typically custom-manufactured from engineered drawings due to their exacting requirements. A.J. Foss manufactures 4-ft. & 5-ft. diameter precast concrete catch basins that are custom made per each project’s requirements.

Drop Inlets (which are a type of catch basin) are ideal for projects that require a pre-fabricated, ready-to-use structure that includes knockouts for on-site adjustments


A manhole does not typically include a sump because it does not have an open top like a catch basin has. Manholes are used in a closed system, while catch basins have openings at the top to allow water to collect in them. A.J. Foss manufactures 4-ft. & 5-ft. diameter manholes that are custom-made per each project’s requirements.

Manhole Uses and Structures

Sanitary sewer systems and storm drain systems use precast circular concrete manholes to provide access, observation and junctions.

Precast concrete manholes are appropriate for:

  • Pump stations
  • Wet wells
  • Stormwater management structures

Loading Requirements

All A.J. Foss-produced manholes and vertical structures are designed and manufactured for H-20 loading.

Manhole sizes

Precast circular manholes are 4-ft or 5-ft in diameter

Uses for precast circular manholes:
  • Access for system maintenance
  • Changes in shape, size, or direction of pipe
  • Observation points
  • Multiple pipe junctions

Uses for precast circular catch basins:

  • Stormwater management
  • Pond overflow structures

Available features of precast circular manholes and catch basins:

Most items are manufactured without inverts; however, with our state of the art stationary coring machine we can core and ship your order with quick turnaround time.

Contact us to discuss your projects throughout New Hampshire, Maine and Northern Massachusetts that require wastewater and stormwater products, and discover the A.J. Foss difference for yourself.

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