How we estimate it
This is a rule of thumb, not an exact figure. We allow about 10 litres of stored hot water for a bucket bath and about 18 litres for a shower, because stored water is mixed with cold. In very cold places we add 25%.
We then pick the next common tank size: 6, 10, 15, 25 or 35 litres.
When to go smaller or bigger
- If people bathe hours apart, the tank reheats between baths, so a smaller one may be enough.
- If the pipe from the geyser is long, more water is wasted before it runs hot.
- A bigger tank takes longer to heat and loses more heat if you keep it on all day.
Next: read Top 5 geysers in India: how to choose.