Water and purification

In the default Apocalypse preset the water cuts out at a random point in the first 30 days. Power has its own separate timer, so they usually fail on different days. Sandbox settings range from Instant to Never, and the Six Months Later preset starts with the water already off. See sandbox settings.

Until then, taps, sinks, baths and toilets give clean water without limit. After the shutoff most fixtures still hold a little leftover water you can collect once.

Opinion Fill every bottle, pot, bucket and water-cooler jug on day one. It costs nothing and buys you weeks.

Build 42 treats clean water and tainted water as different fluids. Rivers, lakes, ponds and rain collectors give tainted water; taps before the shutoff give clean water.

• Mix tainted into clean and the whole container becomes tainted. Adding clean water does not fix it (one source).
• Drinking tainted water causes food-poisoning-style sickness: the Queasy, Nauseous and Sick moodles.
• Tainted water is fine for watering crops, washing and laundry.
• The "tainted water" warning text is itself a sandbox option. It is on by default but off in the Extinction preset.

You cannot build a well in the base game; wells are part of the map.

Collectors must stand under open sky. Build 41 needed Carpentry 4 and 7, so older guides look harder than the game now is.

Plumbing: put a collector one floor above a sink, on the sink's tile or one of the eight around it, then use a pipe wrench on the sink. No electricity is needed. Whether a plumbed sink gives clean or tainted water has changed between updates, and sources disagree for 42.21, so read the sink's tooltip before you drink. Plumbing also drains the sink's own leftover mains water, so bottle that first (one source). More on base layout on base building.

1. Boil it. Put tainted water in a metal pot, kettle, saucepan or metal bucket on a stove, oven or campfire. Bottles and mugs can go in a microwave. It is safe when the tainted warning disappears.
2. Purification tablets. The Purify Water recipe cleans about 1 litre per tablet without any heat. A pack has 20 uses (game files).

Container sizes in Build 42 are in litres: water bottle 1 L, cooking pot and kettle 1.5 L, saucepan 0.6 L, bucket 10 L, water dispenser bottle 15 L. Clean water reduces thirst by about 50 points per litre (one source). The cooking page compares heat sources.