Precast Concrete Manholes
Gainey’s Concrete provides high-quality precast concrete manholes designed for use in sanitary sewer and storm drain systems. Our manholes are built for durability and reliability, serving as essential maintenance access points, observation points, junctions for multiple pipes, and accommodating changes in pipe size or direction. As a trusted precast concrete manhole manufacturer, Gainey’s ensures each product meets industry standards for performance and longevity.
MANHOLE Sizes
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48" Base and Riser
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60" Base and Riser
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72" Base and Riser
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96" Base and Riser
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120" Base and Riser
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144" Base and Riser
accessories and information
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Regular (non-extended) base or extended base sections are available
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Riser sections in 2' - 5'
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Eccentric cones in 1'8", 2’, and 3’ sections
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Concentric cones in 2' and 3' sections
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Grade Rings in 4” and 6” Sections or as Required
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Flexible rubber connectors are available in most sizes to accommodate pipe penetrations
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Interior/Exterior Coating
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Manhole Steps
stock manhole options
Ready whenever you are -Order today!
Add a Top:
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8" Flat Top
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1' 8" Cone (Eccentric)
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2' Cone (Eccentric and Concentric)
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3' Cone (Eccentric and Concentric)
Need to Know Info:
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Meets ASTM C478 Requirements
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Holes can be cored as needed
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1 Roll Conseal Sealant between joints
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We can pour inverts for you
resources
manhole invert systems
Manhole invert channels
Watertight manhole joints
manhole installation guide
grout guide
manhole sizing recommendations
Frequently Asked Questions:
What determines the size of the manhole I need?
Manhole size is driven by:
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The largest pipe diameter
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The number of pipes entering
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The entry angles
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The required structural leg (minimum 6")
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Type of pipe and connector
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If pipes are too close or too large, the manhole must increase in diameter.
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When do I need watertight vs. soil-tight joints?
Use watertight joints when:
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Exfiltration or infiltration is a concern
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Wastewater environments
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Regulated discharge situations
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(ASTM C443 applies – tested to hold 13 psi for 10 minutes with zero leakage)
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Use soil-tight joints when:
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Preventing soil migration is the goal
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Storm systems without pressure needs
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(ASTM C990 applies)
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What are the correct opening requirements and how should pipe connections be sealed?
For soil-tight grouted connections:
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Minimum opening: Pipe O.D. + 2 inches
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Maximum opening: Pipe O.D. + 6 inches
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Pipe should be centered, not resting on the bottom
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Recommended grout: ASTM C1107 hydraulic grout
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Annular space typically 1"–3"
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What are the best practices for installing a manhole so it doesn’t fail?
Critical installation guidelines include:
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Use approved lifting devices / sling angles ≥ 60°
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Bedding foundation: firm soil or compacted base to 90% Proctor
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Foundation extends 6" beyond manhole
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3" minimum leveling course
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Ensure manhole stays level and plumb
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Backfill evenly to prevent tipping
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Vacuum test before backfilling when required
What is an invert and which type do I actually need (standard vs. upsized)?
The invert is the flow channel formed inside the manhole to transition wastewater smoothly between pipes. Good invert design:
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Matches flow diameter of incoming pipe
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Prevents turbulence & sediment buildup
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Reduces scour and erosion risk
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Bench slope should be 0.5"–1.5" per ft, with smooth transitions
