Stored water runs out. This works from the other end — the water you can renew: a roof that catches rain, a well, a spring, a creek you can haul and treat. Set what you have and it works out the gallons a day each one really yields against your household's need, so you can see how much of your water is independent of the tap. For stored jugs and drums, use Food & Water Storage; to make any of it safe to drink, the Water Purification calculator.
These are renewable — a caught, pumped or flowing source keeps producing, so anything above 100% could supply the household indefinitely. Roof and surface water are not drinkable as-is: filter and disinfect them with the Water Purification calculator. Check local law — a few states still restrict large-scale rainwater harvesting.
Stored gallons are tracked in Food & Water Storage — add jugs, drums, a cistern or your water-heater reserve there and they'll show up here. Size a tank to the dry spell, not the yearly total: a wet climate can still leave you short if the rain all falls in three months.
Pair a renewable water supply with a stocked reserve, and keep it in your category plan.
How much of your water keeps coming when the tap stops.
Storage gets you through the shock; renewable sources get you through the long haul. This plans the second half — the water that keeps arriving on its own.
Yields are estimates from typical conditions; a dry month is the real test, so size your buffer for the worst stretch, not the average. Pair it with Food & Water Storage for your stored supply and Water Purification to make any source safe to drink.
