Guide to Safely Burying Polyethylene Water Tanks

Imagine this: your carefully designed garden, its aesthetic harmony disrupted by an unsightly above-ground water tank. Or perhaps you need to maximize limited yard space. Burying the tank underground seems like an ideal solution—but can polyethylene (poly) tanks be safely buried? If so, how?

Unlike steel tanks that corrode when buried, polyethylene tanks offer natural advantages for underground installation. However, not all polyethylene tanks are designed for direct burial. This article examines the feasibility of burying poly tanks and provides complete guidance for creating both functional and visually discreet water storage systems.

Feasibility Analysis of Burying Polyethylene Tanks

Polyethylene—a high-molecular-weight polymer—possesses exceptional corrosion resistance, weather durability, and physical strength. These properties make certain polyethylene tanks suitable for burial under specific conditions. However, standard above-ground tanks shouldn't be directly buried because their designs don't account for soil's lateral pressure.

Partial Burial: Possible With Precautions

Standard above-ground polyethylene tanks can be partially buried, but only with critical caveats. Non-reinforced tanks cannot withstand soil's immense lateral forces. Without proper structural support, buried tanks risk collapsing under external pressure. Therefore, consult qualified engineers before any burial project.

Engineers evaluate soil composition, burial depth, and site conditions to ensure stable foundations and adequate tank support. They provide detailed structural plans and installation specifications to prevent ground erosion and tank deformation.

As general guidance:

• Limit partial burial depth to 1 meter (3.3 feet) maximum
• Excavate pits 300mm (12 inches) wider than the tank's base diameter for backfill material
• For multiple tanks, dig separate pits to prevent mutual interference

Tank foundations require proper preparation with level, compacted bases. Common foundation materials include:

• Bricks
• Concrete slabs
• Gravel beds
• 300-400mm thick compacted dolomite surfaces

Critical Note: Improper installation may void tank warranties and cause structural failure. Always follow manufacturer specifications and consult professionals when uncertain.

Full Burial: Specialized Underground Tanks

While standard tanks aren't designed for complete burial, purpose-built underground polyethylene tanks offer practical alternatives. Compared to concrete cisterns, underground poly tanks typically prove more cost-effective and easier to install. Crucially, their engineered designs withstand subterranean environmental stresses.

Advantages of Underground Poly Tanks

• Superior load-bearing: Reinforced structures resist soil pressure without deformation
• Simplified installation: Lightweight polyethylene facilitates easier handling than concrete alternatives
• Cost efficiency: Often more economical than concrete tanks in comparable applications
• Corrosion resistance: Polyethylene inherently resists chemical degradation in underground environments

Key Installation Considerations

Professional guidance remains essential for underground tank installations. Core steps include:

1. Site evaluation: Conduct soil testing to verify adequate load-bearing capacity
2. Excavation: Dig pits with sufficient clearance for installation and maintenance access
3. Foundation preparation: Create level bases with compacted gravel or concrete
4. Tank placement: Position tanks precisely level, then connect all plumbing components per manufacturer instructions
5. Backfilling: Use granular materials like gravel, compacting in successive layers to ensure uniform support
6. System testing: Verify proper water flow and check for leaks before final backfill completion

Maintenance Requirements

Both partially and fully buried tanks require regular maintenance:

• Periodic inspections: Check for cracks, deformations, or leaks, particularly at connection points
• Tank cleaning: Remove sediment annually (or more frequently depending on water quality)
• Pipe maintenance: Clear debris from inlet/outlet pipes to ensure unobstructed flow
• Freeze protection: In cold climates, insulate tanks and pipes or install heating elements
• UV protection: Although polyethylene resists UV degradation, minimize direct sunlight exposure where possible

Selecting Appropriate Tanks

Key selection criteria for polyethylene tanks:

• Capacity: Match tank volume to anticipated water demand
• Dimensions: Ensure tanks fit available space while allowing proper installation access
• Material quality: Select high-grade polyethylene for optimal durability
• Certifications: Verify compliance with relevant industry standards
• Manufacturer reputation: Choose established brands with reliable technical support

Conclusion

Polyethylene water tanks can be successfully buried when proper procedures are followed. Standard above-ground tanks may accommodate partial burial with professional engineering oversight, while full burial requires specially designed underground tanks. Regardless of installation method, consistent maintenance ensures long-term system reliability.