Description
Septic & Utility Access · Cast Iron Assembly
3″ × 24″ Watertight
C.I. Frame & Cover
A precision-gasketed, bolt-down cast iron access assembly engineered to prevent groundwater infiltration and effluent escape in septic tanks, pump chambers, and pressure-sensitive utility structures. The industry's trusted watertight solution — built to outlast the structure it protects.
Product Overview
Engineered for Zero Infiltration
The Amercast 3″ × 24″ Watertight Cast Iron Frame and Cover is a fully gasketed, bolt-secured access assembly designed where ordinary covers are not enough. A 1/8″ rubber gasket is compressed between a precision-machined seating surface and the cover's underside as the two stainless steel bolts are tightened, creating a continuous sealed interface that blocks groundwater infiltration inward and prevents effluent or odor migration outward.
This assembly is the preferred watertight solution for septic systems operating in high water table environments, coastal and flood-prone zones, and any installation where regulatory compliance or environmental protection standards require a positively sealed access point. The bolt-down configuration also doubles as a security measure, preventing unauthorized or accidental cover removal — a requirement on many commercial and municipal utility projects.
Two model configurations are available: 1084(P) with a plain unmarked cover for versatile applications across sewer, water, and utility access, and 1084(STP) with the word "SEPTIC" cast directly into the cover surface for residential and commercial on-site wastewater systems. Both models share identical dimensional and structural specifications — only the casting designation differs.
Manufactured from gray cast iron meeting ASTM A48 Class 30B standards and finished in black bituminous paint for corrosion resistance, this assembly delivers the same long service life Amercast is known for across its complete line of manhole frames and covers. Frame and cover are reversible (C.I. Frame Reversible designation), and the concealed pick hole on the cover allows single-person removal using a standard pick hook without compromising the watertight surface.
For installations where a standard non-gasketed cover is sufficient, view the 3″ × 24″ Septic Manhole Frame and Cover. For deeper installations or higher riser heights, the 6″ × 24″ Locking Watertight and 4″ × 24″ Locking Watertight provide the same gasket and bolt system with greater frame depth.
How It Works
A Three-Component
Watertight System
Unlike standard manhole assemblies that rely solely on seating fit to limit water intrusion, the 3″ × 24″ Watertight assembly uses a three-component system — a precision-machined seating surface, a full-perimeter rubber compression gasket, and a two-bolt locking mechanism — to create a verified sealed interface under all installation and loading conditions.
The result is an assembly that prevents both infiltration (groundwater entering the structure) and exfiltration (odors or effluent escaping to grade), meeting the performance requirements of ASTM A48 Class 30B gray iron castings.
This configuration is widely specified for septic systems, pump chambers, and grease interceptors where state health codes require watertight access covers, and for municipal utility structures in FEMA flood zones.
Where It's Used
Built for Infiltration-Critical Applications
Any underground structure where groundwater intrusion or effluent escape must be positively prevented — not just minimized — is a candidate for the watertight assembly.
Technical Data
Complete Specifications
| Clear Opening Diameter | 24.0″ |
| Frame Height | 3.0″ (3″) |
| Frame O.D. | 24 5/8″ |
| Outer Flange Diameter | 28.0″ |
| Cover Diameter (O.D.) | 23 3/4″ |
| Cover I.D. (Seating) | 23 1/2″ |
| Cover Thickness | 1 1/8″ |
| Bolt Hole PCD | 22″ |
| Bolt Hole Qty & Size | 2 × 1/2″ BSW |
| Drill Holes (Cover) | 2 × 9/16″ on 22″ PCD |
| Gasket Thickness | 1/8″ |
| Gasket Width | 2 1/4″ |
| Pick Hole | 1″ Concealed |
| Frame Material | Gray Cast Iron |
| Cover Material | Gray Cast Iron |
| ASTM Standard | A48 Class 30B |
| Frame Designation | C.I. Frame (Reversible) |
| Coating | Black Bituminous Paint |
| Gasket Material | Rubber (Compression Type) |
| Traffic Class | Light Duty / Pedestrian |
| Corrosion Resistance | High |
| Freeze-Thaw Resistance | Excellent |
| Service Life (Typical) | 30+ Years |
| Assembly Weight (Approx.) | 145 – 185 lbs |
| Cover Weight (Approx.) | 85 – 115 lbs |
Performance Data
Built to Last. Engineered to Seal.
Ready to Specify or Order?
Same-day response for quotes. CAD drawings and submittals available on request. Custom markings, finishes, and pallet quantities — call us to discuss your project.
516-624-8543
