Factory Direct AASHTO H20 Stormwater Modules

Premium Quality, Unbeatable Price. Engineered to meet US H-20 traffic loading standards with a 50-year design life. Save 30% compared to local distributors by buying direct. US logistics support available.

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Why Choose Our AASHTO H-20 Stormwater Modules

High-capacity replacement for gravel trenches and concrete tanks—engineered for AASHTO H-20 traffic loads and rapid manual installation.

AASHTO H-20 / HS-25 Rated

Engineered for heavy-duty structural integrity. Fully tested to withstand heavy truck loads under commercial parking lots and roadways. Comparable strength to concrete vaults but easier to install.

AASHTO HS-20 load rated underground stormwater detention modules for parking lots

95% Void Ratio (Max Storage)

Delivers 3x the storage volume of stone aggregate (gravel). Maximizes underground water storage in a smaller footprint, significantly reducing excavation costs and soil removal fees.

High void ratio (95%) modular stormwater tanks compared to gravel trenches

Meets US Regulatory Codes

Designed for compliance with Florida “First Flush” retention, California LID infiltration, and Texas flood detention requirements. Accepted by engineers and municipalities nationwide.

Stackable stormwater storage modules for flexible underground basin design

100% Recycled Polypropylene

Made from industrial-grade recycled PP. Resistant to road salts, fuel spills, and soil chemicals. Helps projects achieve LEED credits for Sustainable Sites (SS) and Materials.

Recycled polypropylene (PP) material for sustainable LID stormwater systems

Rapid “Snap-Lock” Installation

Lightweight modules require no heavy cranes. Two workers can install 4,000 cubic feet per day using our tool-assisted assembly. Drastically cuts down labor hours and project timelines.

ersatile configuration for infiltration dry wells or detention tank systems

Inspectable & Maintainable

Compatible with standard “Isolator Row” designs. Wraps a row in geotextile to trap sediment, allowing for easy cleaning via inspection ports and Jet-Vac trucks.

Stormwater system inspection ports and sediment traps for easy maintenance

Configurations: Infiltration & Detention for Reuse

Infiltration & Soakaway System

Goal: Groundwater Recharge / Zero Discharge.

Lining: Wrap the entire module array in AASHTO Class 2 non-woven permeable geotextile.

Base: Place on a 6-inch leveled layer of clean, angular crushed stone.

Function: Allows water to exfiltrate freely into the subsoil. Perfect for LID compliance and septic leach fields.

Detention & Flood Mitigation

Goal: Peak Flow Reduction / Flood Control.

Lining: Seal with a watertight impermeable geomembrane (HDPE/LLDPE) protected by a fleece layer.

Control: Install a flow control manhole (orifice/weir) to restrict discharge rates to municipal sewers.

Use Case: Ideal for Texas/Houston flood zones or sites with non-draining clay soils.

Essential Pretreatment

Content: To ensure longevity, install upstream silt traps, hydrodynamic separators, or leaf baskets. This captures debris before it enters the tank, keeping the infiltration basin efficient.

Diagram of shallow vs deep underground stormwater detention and infiltration systems

Technical Specifications (AASHTO H-20 Rated)

Engineered to exceed AASHTO HS-20 & HS-25 structural load standards. Fully certified for heavy-duty traffic applications under commercial parking lots, fire lanes, and roadways.

Stormwater Module 6841 (17.7″ Height)

Stack	Size (mm)	Tank Volume (ft³)	Tank Volume (gal)	Net Water (ft³)	Net Water (gal)
Single	26.8 × 16.1 × 17.7 in (680 × 410 × 450 mm)	4.44	33.22	4.31	32.21
Double	53.5 × 16.1 × 17.7 in (1360 × 410 × 450 mm)	8.89	66.44	8.63	63.05
Triple	80.3 × 16.1 × 17.7 in (2040 × 410 × 450 mm)	12.93	97.62	12.54	93.81
Quad	107.1 × 16.1 × 17.7 in (2720 × 410 × 450 mm)	17.17	128.47	16.65	124.58
Pent	133.9 × 16.1 × 17.7 in (3400 × 410 × 450 mm)	21.42	160.21	20.78	155.41

Stormwater Module 8053 (20.9″ Height)

Stack	Size (mm)	Tank Volume (ft³)	Tank Volume (gal)	Net Water (ft³)	Net Water (gal)
Single	31.5 × 19.3 × 20.9 in (800 × 490 × 530 mm)	6.02	45.12	5.84	43.76
Double	63.0 × 19.3 × 20.9 in (1600 × 490 × 530 mm)	12.04	90.24	11.68	87.52
Triple	94.5 × 19.3 × 20.9 in (2400 × 490 × 530 mm)	18.06	135.36	17.52	131.28
Quad	126.0 × 19.3 × 20.9 in (3200 × 490 × 530 mm)	24.08	180.48	23.36	175.04
Pent	157.5 × 19.3 × 20.9 in (4000 × 490 × 530 mm)	30.10	225.60	29.20	218.80

Material & Structural Ratings

Material: 100% Industrial Grade Recycled Polypropylene (Virgin PP available for specific projects).

Load Rating: AASHTO H-20 / HS-25 (Certified for 40,000 lbs axle loads under parking lots & roadways).

Chemical Resistance: Unaffected by road salts, fuels, oils, and naturally occurring soil alkalis/acids.

Temperature Range: -22°F to 248°F (-30°C to 120°C).

Hydraulic Performance

Void Ratio: 95% Net Void Space (Maximizes storage volume to minimize excavation footprint).

Applications: Designed for Underground Detention (Flood Control), Infiltration Basins, and Rainwater Harvesting.

Connections: Universal compatibility with 4″-12″ Schedule 40 PVC and Standard Corrugated HDPE pipes.

Engineering Support & Resources

Material Color: Standard Industrial Black (UV Stabilized Recycled PP).

Resources: Full CAD details, step-by-step installation guides, and submittal packages available upon request.

Need a stamped layout and cover design for H-20/HS-20?

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Field Assembly & Installation Guide

Tool-assisted snap assembly: Build rugged underground basins in minutes without heavy cranes or specialized machinery.

Insert the large pegs of a small plate into the holes of a large plate to form the first side.

Repeat with remaining small plates along the large plate, creating the vertical sides.

Place the second large plate on top to complete the side frame.

Rotate the unit so large plates are on the sides (top & bottom open).

Align a large plate to the pegs of the vertical small plates and tap into place using a 2×4 and dead‑blow hammer.

Flip the unit and tap the final large plate to close the crate (Single complete).

For multi‑stack (Double/Triple/Quad/Pent): flip, align the next crate with open end, and repeat; confirm engagement.

EQUIPMENT

FAQ — Stormwater Module Systems

Are these modules traffic rated? Can they support heavy trucks?

Yes. Our modules are engineered and tested to meet AASHTO H-20 and HS-25 structural load standards. When installed with the correct cover depth and engineered backfill, they are fully certified for use under commercial parking lots, fire lanes, and roadways.

Does this system meet local municipal and state stormwater codes?

Absolutely. Our systems are designed to comply with major US stormwater mandates, including Florida’s ERP “First Flush” retention, California’s LID (Low Impact Development) infiltration requirements, and Texas flood detention standards. We can provide technical data sheets to help you get permit approval.

Can I use these modules for an Infiltration Basin or Dry Well?

Yes. Simply wrap the module assembly in AASHTO Class 2 non-woven geotextile. This allows stormwater to rapidly exfiltrate into the surrounding soil, making it ideal for groundwater recharge and meeting local LID (Low Impact Development) requirements.

Can I use this for a Septic Leach Field or Drain Field replacement?

Absolutely. In the US, these open-bottom modules are increasingly used for chamber leach fields. They provide a massive soil contact area for effluent to percolate into the ground. They are lightweight, easy to snap together, and offer a much higher capacity than standard corrugated leach pipes, making them ideal for septic system upgrades in limited spaces.

My site has a high water table. Can I install a shallow system?

Yes, the design is flexible. If you hit water or bedrock after digging just a few feet, you can install our modules in a single-layer “flat” configuration. This creates a shallow infiltration basin that spreads water out horizontally, keeping your system above the groundwater table while still managing heavy roof runoff or “First Flush” retention requirements (common in Florida).

How do I prevent the system from clogging?

Pretreatment is key. Always install a standard Catch Basin or leaf filter before water enters the tank. We also recommend using an “Isolator Row” design—wrapping the first row of modules in fabric to trap sediment. This acts as an internal filter that is easily cleaned with a Jet-Vac truck, ensuring long-term performance.

Can I use this system to harvest rainwater for my garden?

Yes, it works as an underground cistern. By wrapping the modules in a waterproof geomembrane (tank liner), you create a watertight underground water tank. You can then install a submersible pump to reuse the water for garden irrigation, toilet flushing, or car washing. It’s a great way to hide your water storage under a lawn or driveway without losing surface space.

Project Gallery: Detention & Infiltration Installations.

See our modular systems in action—from heavy-duty AASHTO H-20 parking lot basins to high-capacity residential dry wells.

Large scale underground stormwater detention basin installation for commercial site

Wrapping modular infiltration tanks with non-woven geotextile fabric

Assembling modular stormwater storage units for residential drainage

Underground water retention system installation for flood mitigation

HS-20 rated stormwater modules installed under roadway infrastructure

Finished underground stormwater tank system ready for backfill

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