Heavy-Duty Septic Tank

Heavy-Duty Poly Septic Tanks

Engineered for Deep Burial, High Water Tables & Demanding Sites

When your project demands exceptional strength and long-term performance, upgrade to heavy-duty poly septic tanks. These underground septic tanks feature an engineered ribbed wall design, high-grade polyethylene and a one-piece, pre-plumbed construction that stands up to deeper burial, challenging soils and higher loads. Heavy-duty septic tanks are available in single and dual compartment models to match your septic system design, and each tank is backed by a limited lifetime warranty and broad state approvals.

Heavy-Duty Poly Septic Tanks Features

• Engineered ribbed strength: Heavy-duty septic tanks use a reinforced ribbed design that resists soil and groundwater pressure, making them ideal for deeper burial, high water table sites and areas with occasional traffic or equipment loads.
• High-grade polyethylene construction: Tanks are molded from non-reprocessed polyethylene, not recycled plastic, for consistent strength and performance. The plastic material will not rust and is resistant to sulfuric acid decay that can damage concrete septic tanks.
• One-piece, pre-plumbed design: Each heavy-duty septic tank ships as a single-piece system with inlet, outlet and internal plumbing already installed. There is no internal skeleton to assemble, which improves structural integrity and saves time on site.
• Lightweight and easy to handle: Compared to concrete septic tanks, these heavy-duty poly tanks are much lighter, easier to transport and can often be set with smaller equipment. The flat bottom design simplifies bedding and leveling in the excavation.

• Built for challenging conditions: Designed for use in high water table areas and deeper burial depths, heavy-duty septic tanks offer dependable performance in demanding soil and site conditions.
• Limited lifetime warranty: AK Industries backs these plastic septic tanks with a limited lifetime warranty—one of the strongest warranties in the poly septic tank market.

For projects with standard burial depths and lighter duty requirements, see our Standard Septic Tanks.

Septic Tank Sizes

Please Note: Not all Heavy-Duty Tanks are listed. All dimensions referenced above are available for purchase.

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Septic Tanks Flyer

Applications of Heavy-Duty Septic Tanks

Heavy-duty poly septic tanks are selected when site conditions or design requirements go beyond what a standard duty septic tank can handle. The reinforced ribbed wall design, high-strength polyethylene material and one-piece construction make these underground septic tanks a great fit for:

• Deep-burial septic systems: Sites where the septic tank must be buried deeper than typical residential installations, within the manufacturer’s approved burial depth.
• High water table and challenging soils: Coastal areas, saturated soils and locations where tank flotation and external pressure are a concern.
• Driveway and light traffic areas: Installations where tanks may see occasional vehicle or equipment loading, subject to local code and the manufacturer’s load guidelines.
• Commercial and industrial projects: Restaurants, small industrial facilities, offices and other higher-use properties that require robust septic tank performance.
• Agricultural and rural sites: Farm and ranch buildings, worker housing and remote facilities that need durable, long-lasting septic tanks.

For systems that also require a lift station or pressure dosing, pair a heavy-duty septic tank with one of our pump septic tanks and compatible septic tank accessories.

State Approvals, Warranty & Support

Our Heavy-duty septic tanks are approved for use in nearly every state and carry both IAPMO and CSA certifications. Each model has state-specific approval letters available for installers, designers and inspectors.

When you open any heavy-duty septic tank product, use the state selector on the product page to verify that tank is approved in your state and to access approval documentation. If you do not see your state listed, contact our team and we will help you review available options.

Heavy-Duty Septic Tank Installation Overview

Always follow local septic system codes and the manufacturer’s full installation instructions. In general, proper installation of a heavy-duty poly septic tank includes:

• Excavating the tank hole with 6–12 inches of clearance on all sides.
• Placing 6–12 inches of level, compacted gravel or aggregate in the bottom of the excavation.
• Setting and leveling the septic tank, then installing risers if required.
• Backfilling evenly around the tank with clean gravel while adding water inside the tank at the same rate.
• Bringing gravel up to the top of the tank, then finishing with approximately 6 inches of topsoil to final grade.

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