Overhead and underground water tanks in Pakistani homes are sold by capacity in gallons, while water use is often discussed in litres. Pick a tank too small and you run out during load-shedding or supply breaks; too big and you waste money and space. This guide explains water tank sizes in gallons and liters and how to estimate what your home needs, with our Liters to Gallons converter.
Which gallon?
Local tank makers commonly use the imperial (UK) gallon of 4.546 L, but some use the US gallon of 3.785 L. Ask the seller, because it changes the real capacity by about 20%.
Common tank sizes
| Tank size | Imperial (L) | US (L) |
|---|---|---|
| 300 gallons | 1,364 | 1,136 |
| 500 gallons | 2,273 | 1,893 |
| 750 gallons | 3,410 | 2,839 |
| 1,000 gallons | 4,546 | 3,785 |
| 2,000 gallons | 9,092 | 7,571 |
How much water does a home use?
Use varies with family size, bathrooms, gardens and habits. A rough planning range is about 100 to 150 litres per person per day for household use in cities, but your own use may differ.
Example: a family of 6 using 120 L each = 720 L a day.
How many days should the tank last?
If supply comes every day, one to two days of storage is usually enough. If water comes on alternate days or supply is unreliable, plan for two to three days.
720 L × 2 days = 1,440 L, which suits a 300- to 500-gallon imperial tank.
Overhead vs underground tanks
Many houses have an underground tank filled by the municipal supply and an overhead tank filled by a pump. The underground tank is usually larger, holding several days of water, while the overhead tank holds a day or less.
Tank dimensions
Volume = length × width × height. A tank 1.5 m × 1.2 m × 1.2 m holds 2.16 m³, which is 2,160 litres. For rectangular volumes in other units, the Box Volume Calculator gives cubic metres, litres and cubic feet.
Saving water
Fix leaking taps and flush tanks, use buckets for washing cars, and water gardens in the evening. Small habits reduce how big a tank you need. For the conversion formulas, see how to convert liters to gallons.
Pumping time
To estimate how long a pump takes to fill a tank, divide the tank’s capacity by the pump’s flow rate. A 2,273-litre tank filled by a pump delivering 40 litres per minute takes about 57 minutes, ignoring height and pipe losses. If your pump’s rating is in gallons per minute, convert it first with the formulas in this article, and use the Online Timer to remind you to switch the pump off.
Frequently asked questions
How many liters is a 500-gallon tank?
About 2,273 L if imperial gallons, or 1,893 L if US gallons.
What size water tank does a family of 5 need?
Often around 300 to 500 imperial gallons for overhead storage, depending on use and supply.
How do I calculate tank capacity from dimensions?
Multiply length × width × height in metres and multiply by 1,000 for litres.