What Size Water Tank for a House in Thailand?
Figures reviewed 14 October 2026
Why Thai homes have water tanks
Outside central city areas, mains water pressure can be low, and supply interruptions happen. Many houses use a storage tank that fills from the mains, plus a pump that pushes water to the taps. When the supply stops, the tank keeps the household going.
The real question isn't just how many people live in the house. It's how many days you want to cover if the supply stops.
Tank size table
This table assumes 50 litres per day of extra use (cleaning, plants) and that 90% of the tank is usable, because the outlet and pump sit above the tank's base. Figures are the minimum capacity printed on the tank's label.
| People | 100 L/person, 1 day | 100 L/person, 2 days | 150 L/person, 1 day | 150 L/person, 2 days |
|---|---|---|---|---|
| 2 | 278 L | 556 L | 389 L | 778 L |
| 3 | 389 L | 778 L | 556 L | 1,111 L |
| 4 | 500 L | 1,000 L | 722 L | 1,444 L |
| 5 | 611 L | 1,222 L | 889 L | 1,778 L |
| 6 | 722 L | 1,444 L | 1,056 L | 2,111 L |
Pick the next tank size on sale at or above your figure.
Use your water bill instead of guessing
One unit on a Thai water bill (from MWA in Bangkok or PWA elsewhere) is 1 m³, which is 1,000 litres.
Litres per day = units used × 1,000 ÷ days in the billing period
Example: 18 units in 30 days = 600 litres per day. For 2 days of storage: 600 × 2 ÷ 0.9 = 1,333 L, so choose the next tank size up.
Before installing
Weight: 1,000 litres of water weighs about 1,000 kg, before the tank itself. Rooftop or raised stands need checking by an engineer or a qualified builder.
Pump: match the pump to the tank and the height it needs to push water. A pump running with no water in the tank can be damaged.
Hygiene: use a tight lid against mosquitoes and debris, and clean the tank regularly. If you plan to drink the water, test it and filter it separately.
Renters: ask the landlord how big the tank is and how often it's cleaned. It's a reasonable question before signing.
FAQ
Can I collect rainwater too? Yes. Use the rainwater calculator (/en/calculators/rainwater/) to see how much your roof can collect.
Estimate a tank for four people