Calculator Inputs
Example Data Table
| Scenario | Tank type | Dimensions | Fill | Occupants | Days | Usable (L) | Recommended (L) |
|---|---|---|---|---|---|---|---|
| Residential block | Rectangular | L=2 m, W=1.5 m, H=2 m | 98% | 6 | 2 | 5,880 | 1,782 |
| Small facility | Vertical cylinder | D=2 m, H=3 m | 95% | 18 | 2 | 8,953 | 5,346 |
| Site storage | Horizontal cylinder | D=2.2 m, L=4 m | 90% | 0 | 0 | 13,676 | 0 |
Formula Used
Geometric Volume
- Rectangular: V = L × W × H
- Vertical cylinder: V = π × (D/2)² × H
- Horizontal cylinder: V = π × (D/2)² × L
- Sphere: V = 4/3 × π × R³
- Frustum: V = πH/3 × (R² + Rr + r²)
Recommended Storage
Base demand: Occupants × LPD × Days
Add reserves: Base + Fire reserve
Add contingency: (Base + Reserves) × (1 + Contingency%)
How to Use This Calculator
- Select the tank shape and measurement units.
- Enter the dimensions that apply to your chosen shape.
- Set the number of tanks and expected fill percentage.
- Enter occupants, daily liters per person, and storage days.
- Add a fire reserve and contingency if required.
- Press Calculate to see results above the form.
- Use the export buttons to download CSV or PDF.
Demand planning for buildings
Daily demand is typically expressed as liters per person per day (LPD) and multiplied by occupants and storage days. In this calculator, the recommended storage equals occupants × LPD × days, then fire reserve is added. A contingency percentage is applied to cover peak periods, leakage, and future occupancy. Use higher LPD for facilities with kitchens, laundries, or showers, and lower values for low-occupancy sites.
Geometry options and units
Tank volume depends on shape. Rectangular tanks use L × W × H, cylindrical tanks use π × (D/2)² × length or height, spheres use 4/3 × π × R³, and frustums use πH/3 × (R² + Rr + r²). Inputs can be entered in meters, centimeters, millimeters, feet, or inches. The tool converts dimensions to meters and reports capacity in liters and US gallons.
Usable storage and operational margins
Installed capacity is not always usable capacity. Freeboard, inlet turbulence, sludge allowance, and maintenance drawdown often reduce available water. The fill percentage control models this by multiplying full volume by your chosen percent and the number of tanks. For critical projects, consider separate compartments or multiple tanks to maintain service during cleaning or repairs.
Fire reserve and compliance checks
Fire reserve requirements vary by risk, building height, and local rules. Enter the fire reserve as a fixed volume so the recommended target reflects both domestic and fire needs. The result summary compares usable volume against the recommended storage and reports any shortfall. Use the shortfall value to iterate dimensions, add tanks, or adjust the storage days scenario.
Documentation and handover outputs
Construction teams often need a clear sizing record for approvals and handover manuals. After calculating, export a CSV for quick review in spreadsheets or a PDF for sharing with stakeholders. Record the selected shape, units, fill percentage, demand assumptions, and reserves alongside final dimensions. Recalculate after design changes, occupancy updates, or revised fire strategy. Include duty notes, turnover targets, and overflow levels. A common practice is to size domestic storage so at least one full turnover occurs every 24–48 hours, reducing stagnation and odor risks in hot climates.
FAQs
What does fill percentage represent?
It estimates usable water after freeboard, sludge space, and operational drawdown. The calculator multiplies full volume by this percentage and the number of tanks to report usable storage.
Which tank type should I choose?
Pick the geometry that matches your design drawings. Rectangular suits underground tanks, cylinders suit aboveground tanks, spheres and frustums suit special vessels. If unsure, start with the closest shape and refine later.
How is recommended storage calculated?
Recommended storage equals occupants × liters per person per day × storage days. The calculator then adds any fire reserve and applies a contingency percentage to create a practical target volume.
Can I size only for capacity without demand?
Yes. Set occupants and days to zero, then the recommended target becomes zero. You can still use the tool to compute tank capacity and export the results for documentation.
Why is my result below the target?
Your usable volume may be reduced by fill percentage, small dimensions, or too few tanks. Increase dimensions, add tanks, raise fill percent if allowable, or adjust demand assumptions to match the project brief.
Is this compliant with local codes?
This tool provides engineering estimates. Always confirm liters per person, storage days, and fire reserve with local regulations and the project’s authority having jurisdiction before finalizing the tank schedule.