What is a Plastic Polyethylene Water Tank?
A plastic water tank is a lightweight, UV-stabilized rotational-molded polyethylene container used for hygienic drinking water storage, rainwater collection, and chemical storage. Plastic tanks are rust-proof, durable, and easy to transport and install.
For drinking-water contact and tank material standards, refer to the NSF Drinking Water System Components listings.
Plastic Water Tank Volume Formulas
Round (Cylindrical) Poly Tank:
Volume (V) = π × (Diameter / 2)² × Height
Rectangular Poly Tank:
Volume (V) = Length × Width × Height
Conical Bottom Poly Tank:
Volume (V) = [π × (Diameter / 2)² × Cylinder Height] + [⅓ × π × (Diameter / 2)² × Cone Height]
Litres Conversion:
Capacity (Litres) = Volume in m³ × 1,000
How to Calculate Plastic Water Tank Capacity
- Measure Outer / Inner Diameter: Measure tank diameter at mid-height.
- Measure Overall Height: Record vertical wall height from base to top overflow line.
- Calculate Cubic Volume: Multiply circular base area by height.
- Convert to Storage Units: Convert cubic meters to Litres or Gallons.
Plastic Tank Numerical Example
For a vertical poly water tank measuring 6 ft diameter and 7 ft height:
Radius r = 3 ftTotal Volume = 3.14159 × (3)² × 7 = 197.92 ft³Capacity in US Gallons = 197.92 × 7.48052 ≈ 1,480.54 US GallonsCapacity in Litres = 1,480.54 × 3.78541 ≈ 5,604.45 Litres
Standard Poly Water Tank Dimensions & Capacity Chart
| Poly Tank Size | Typical Diameter × Height | Capacity (Litres) | Capacity (US Gal) |
|---|---|---|---|
| 500 Litre Poly Tank | 0.86m × 0.95m (2.8ft × 3.1ft) | 500 L | 132 gal |
| 1,000 Litre Slimline Tank | 0.75m × 1.80m (2.5ft × 5.9ft) | 1,000 L | 264 gal |
| 2,500 Litre Poly Tank | 1.45m × 1.60m (4.8ft × 5.2ft) | 2,500 L | 660 gal |
| 5,000 Litre Round Poly Tank | 1.85m × 1.95m (6.1ft × 6.4ft) | 5,000 L | 1,320 gal |
| 10,000 Litre Commercial Poly Tank | 2.35m × 2.40m (7.7ft × 7.9ft) | 10,000 L | 2,640 gal |
BPA-Free Food Grade Polyethylene & UV Stabilization
Plastic water storage tanks used for drinking water must be constructed from food-grade virgin high-density polyethylene (HDPE) with UV-20 stabilization to prevent algae growth and plastic degradation under direct sunlight.
Polyethylene Tank Structural Features & Capacity
Plastic (polyethylene) water tanks are lightweight, UV-stabilized, and corrosion-resistant. Internal or external ribbing adds structural strength, slightly altering internal geometry. Always calculate net usable capacity up to the overflow fitting height.