Description
24″ × 24″ Heavy Duty Cast Iron Catch Basin Frame & Grate
The Amercast 24″ × 24″ Heavy Duty Cast Iron Catch Basin Frame and Grate (Item 1132) is one of the most widely used and specified catch basin assembly in North American commercial and municipal stormwater infrastructure. Engineered for high-capacity surface drainage in parking lots, roadways, industrial sites, and public right-of-way installations, this assembly combines an H-20 wheel-load rating with a reversible frame design and a longitudinally slotted grate for maximum hydraulic efficiency.
Cast from grey iron conforming to ASTM A48 Class 30B and compliant with AASHTO M306, the 1132 meets the same load and material standards specified by state DOTs, county engineers, and municipal public works departments across the country. The reversible frame installs with the flange either above or below the basin rim — giving contractors flexibility on retrofit and new-construction projects without additional hardware or frame modification. The grate carries the "Dump No Waste — Drains to Waterways" environmental awareness message cast into both faces, satisfying many MS4 stormwater permit marking requirements under the EPA Clean Water Act.
Built for Performance. Proven in the Field.
Complete Specifications — Item 1132
| Item Number | 1132 (24×24) |
| Frame Opening (nominal) | 24″ × 24″ |
| Outer Frame Width (B) | 29‑1/2″ |
| Frame Seat Diameter (C) | 23‑1/2″ |
| Clear Opening (D) | 22‑1/4″ |
| Frame Height (E) | 3‑1/2″ |
| Grate Width (F) | 23‑3/4″ |
| Frame Lip Overhang (X) | 1‑1/4″ |
| Material | Grey Cast Iron |
| ASTM Standard | ASTM A48 Class 30B |
| Load Standard | AASHTO M306 |
| H-20 Proof Load | 40,000 lbs (1 minute sustained) |
| Test Contact Area | 9″ × 9″ grate center |
| Safety Factor vs H-20 | 2.5× (16,000 lb single wheel) |
| Frame Type | Reversible — top or bottom flange |
| Grate Pattern | Slotted — longitudinal |
| Environmental Marking | Dump No Waste / Drains to Waterways (both faces) |
| Compressive Strength | Minimum 30,000 psi (ASTM A48 Class 30B) |
| Corrosion Resistance | High — natural iron-oxide patina |
| Freeze-Thaw Resistance | Excellent |
| Typical Service Life | 30+ years |
| Availability | In Stock |
C = Frame seat / seating ring width — 23‑1/2″
D = Clear opening (usable drain area) — 22‑1/4″
E = Overall frame height — 3‑1/2″
F = Grate overall width — 23‑3/4″
X = Frame lip / overhang depth — 1‑1/4″
Where the 24×24 Is Specified
The 24″ × 24″ is the single most common catch basin size in North American commercial and municipal stormwater infrastructure. If a site handles traffic and needs to drain fast, this is the assembly civil engineers reach for first.
Cast with the Message That Protects Waterways
Storm drains do not connect to treatment plants — everything that enters a catch basin grate flows directly to streams, rivers, and coastal waters. The Amercast 1132 grate carries a permanent environmental awareness message on both faces of the casting:
Permanent — cast iron, never fades or peels · Satisfies EPA MS4 storm drain marking requirements
Required by many state DOT, county, and municipal stormwater management plans
This marking satisfies the storm drain identification requirements of many MS4 (Municipal Separate Storm Sewer System) permit holders operating under EPA NPDES stormwater regulations (40 CFR Part 122). Many county stormwater management plans and state DOT standard specifications explicitly require this or equivalent language to be cast directly into publicly accessible grate surfaces. Custom markings, municipal logos, and utility designations are available — contact us for custom casting options.
Field Notes for Contractors & Engineers
Also Available from Amercast
24″ × 24″ Heavy Duty Catch Basin Frame & Grate — ADA Compliant Version
Browse All Catch Basin Frames & Grates
Inlet Frames & Grates
Manhole Frames & Grates
Manhole Frames & Covers
Precast Catch Basins — Also Available
Common Questions About the 24×24 Catch Basin Frame & Grate
What does H-20 wheel load rating mean?
H-20 refers to an AASHTO highway truck loading designation where each rear axle carries 32,000 lbs, producing a maximum single wheel load of 16,000 lbs. AASHTO M306 requires drainage castings rated for H-20 to pass a 40,000-lb proof load test (2.5× the wheel load) applied to a 9″ × 9″ area at the center of the grate for one sustained minute without permanent deformation or failure.
What is the difference between the standard and ADA versions?
The standard 1132 uses a wider longitudinal slot pattern optimised for maximum hydraulic capacity. The ADA version uses narrower slots (≤ 0.5″ perpendicular to the primary direction of travel) that meet ADA and PROWAG accessibility requirements for bicycle-safe and wheelchair-safe grate openings. Both carry the same H-20 load rating.
Will this fit my existing precast concrete catch basin?
The 24×24 is the most standardised catch basin opening in North America. The Item 1132 frame has a 29‑1/2″ outer flange width and a 23‑1/2″ seating ring (dimension C), which fits standard 24″ precast concrete catch basin structures from most major manufacturers including Oldcastle, Forterra, and Jensen Precast. The reversible frame accommodates varying riser heights. Confirm your existing basin's top opening and riser height before ordering for retrofit applications.
Can Amercast provide custom markings or logos?
Yes. Amercast can cast custom municipal logos, utility company branding, and custom lettering directly into the grate surface. Our design team provides CAD renderings and approval drawings prior to production. Contact [email protected] or call 516-624-8543 to discuss custom casting requirements.
Is cast iron better than plastic or composite grates?
For H-20 traffic-bearing applications, grey cast iron conforming to ASTM A48 Class 30B is the engineering standard. Cast iron provides higher compressive strength (minimum 30,000 psi), superior vibration dampening that eliminates rattle and noise under traffic, and a 30+ year service life without degradation from UV exposure, freeze-thaw cycles, or chemical exposure. Composite and plastic alternatives are generally limited to pedestrian-only or light-duty applications and are not suitable for road or parking lot installation.
