Underground Water Tank
An underground water tank is a hidden storage service located below the ground surface, which is built to collect and store water for different purposes (e.g., domestic supply, irrigation, fire protection, rainwater harvesting, etc.). Underground water tanks are usually made from reinforced concrete, polyethylene, or fiberglass and are often a good solution in areas with limited surface space or design restrictions. When buried, they are protected from sunlight, temperature fluctuations, and other external impacts, helping keep water quality and durability. Underground water tanks are often a good solution in urban areas characterized by smaller housing lots or design efficiency for water use.
The BDF water tank is a structural form that is highly suitable for underground water tanks
1. High Structural Strength
The outer layer of BDF water tanks, constructed from hot-dip galvanized steel, provides superior strength and impact resistance. Under underground water tank applications, the surrounding soil, standing water and external forces from above (e.g. vehicles, construction) will exert significant pressure on the tank, so having an outer layer that will maintain its structural integrity is vital.
2. Corrosion Resistance
Zinc-Coated Steel: The galvanized steel coating is highly resistant to rust and corrosion, which is especially important for underground water tanks exposed to moisture, soil acids, and other environmental factors.
Stainless Steel Interior: The tank’s inner lining is typically made from food-grade stainless steel (e.g., SUS304), ensuring the water stored in the tank remains clean and free from contaminants. This is critical for underground water tanks used for drinking water or rainwater harvesting.
3. Water Tightness and Leak-Proof
Sealed Joints and Gaskets: The joints between the panels are sealed with rubber gaskets and bolted connections, ensuring tight seals and preventing any water leakage. This is particularly crucial for underground tanks, where leaks can cause soil erosion or contamination.
4. Thermal Insulation
Composite Layer: The middle bonding layer in BDF tanks, often made from insulating materials like foam or resin, provides thermal insulation. This helps maintain the water’s temperature, especially in underground installations where temperature fluctuations can be extreme.
The insulation also helps prevent frost damage to the tank in cold climates.
5. Durability and Low Maintenance
BDF tanks are exceptionally robust and can remain intact for an extended period with limited maintenance. Their durability against corrosion and physical stresses makes them the dependable choice for underground water storage, where maintenance is both challenging and costly.
Long lifespan: The combination of high-quality materials and construction ensures a long service life, even in challenging underground environments.
BDF Water Tank Material Composition
Inner Layer – Stainless Steel (B Layer)
Material: SUS304 or SUS316 food-grade stainless steel
Purpose:
Direct contact with stored water
Ensures hygiene, no rust, and no contamination
Resistant to corrosion, heat, and chemical exposure
Outer Layer – Galvanized Steel (D Layer)
Material: Hot-dip galvanized steel sheet
Purpose:
Provides mechanical strength and structural support
Protects the tank from external forces like soil pressure (especially in underground applications)
Middle Layer – Composite Bonding Layer (F Layer)
Material: Polyurethane (PU) foam, resin adhesive, or high-performance bonding material
Purpose:
Bonds the inner and outer layers firmly together
Provides thermal insulation (reduces temperature fluctuations)
Enhances overall durability and energy efficiency
comparison chart between underground and above-ground water tanks
| Feature | Underground Water Tank | Above-Ground Water Tank |
|---|---|---|
| Installation | Requires excavation and more structural planning | Easier and quicker to install |
| Space Usage | Saves above-ground space | Occupies visible land space |
| Aesthetics | Hidden from view, landscape-friendly | Visible; may affect aesthetics |
| Temperature Stability | Naturally insulated, maintains stable temperature | Prone to temperature changes (can freeze or overheat) |
| Evaporation Loss | Minimal evaporation due to lack of exposure | More evaporation, especially in hot climates |
| Structural Requirements | Must withstand soil pressure and possibly traffic load | Only needs to support water weight |
| Maintenance Access | More difficult; requires manhole access | Easy to inspect and repair |
| Water Quality Protection | Protected from surface contaminants | More exposed to debris, dust, and animals |
| Durability | Long-lasting if well-constructed and sealed | Easier to monitor and repair if issues arise |
| Cost | Generally more expensive due to excavation | Lower initial cost |
| Use Cases | Rainwater harvesting, fire reserves, space-saving | Domestic use, agriculture, emergency backup |
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