Water Tank Size Calculator
Instant · no signup neededSize your water storage tank based on your household size and how many days of backup you want to plan for.
Based on 150 liters per person per day — a realistic average for an urban Pakistani household with regular bathing, cooking, and flushing — times your backup days, plus a 20% buffer for evaporation and cleaning losses. Adjust upward for gardens, extra bathrooms, or guests.
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Worked Lahore Example: Sizing Water Storage for a 6-Person Household.
Daily reserve calculation.In Lahore residential sectors such as Johar Town, Wapda Town, or DHA, WASA municipal supply or society tubewells operate on intermittent pumping schedules (usually 2 to 3 hours morning and evening). Sizing storage for an average family of 6 people with 2 full days of emergency backup storage prevents water outages during summer load-shedding or feeder repairs.
Engine Calculation (6 Occupants × 2 Days Backup).
- Baseline Daily Consumption: 6 people × 150 liters/day = 900 liters/day.
- Two-Day Reserve: 1,800 liters.
- Buffer Allowance (+20% safety margin): 360 liters extra.
- Recommended Total Storage: 2,160 liters (475 imperial gallons).
Splitting the storage.
One way to divide the 2,160 liters is two-thirds in an underground tank (1,440 liters, about 317 gallons, roughly 51 cu ft of internal volume) and one-third in an overhead tank (720 liters, about 158 gallons). The overhead tank feeds the taps by gravity and is refilled from the underground tank by pump, and keeping it smaller limits the load on the roof slab. The right split for your house depends on the supply timing and the roof structure, so confirm it with your engineer.
Frequently asked questions
150 liters per person per day — a realistic average for an urban Pakistani household with regular bathing, cooking, and flushing — plus a 20% buffer for evaporation and cleaning losses.
Yes — this is a baseline household estimate. Adjust the tank size upward if you have a garden, extra bathrooms, or regularly host guests.
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