Sources
Every rule, price and figure on TankAtlas links to one of these pages. 46 were opened again on 13 Nov 2026 for this version; the rest come from our research earlier in November 2026. Sentences without a link are our own advice or assumptions, and say so.
Our assumptions
We count 80% of the rain that falls on a roof, to allow for first flush and overflow. We use 60 L a person a day for toilets and laundry, and the BASIX benchmark of 247 L a person a day for a whole house (BASIX). Dry spells of 30 or 60 days in the quick calculator are planning choices, not forecasts.