23.3 What fails and in what order

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When the power goes out for a long time, systems do not all fall at once. They fail in a cascade, depending on how much backup each one has. The exact order varies; this is the typical pattern from real cases.

Figure 23.1. Typical cascade of failures in a prolonged blackout. — **Figure 23.1.** Typical cascade of failures in a prolonged blackout.

What fails and in what order
System	Why it fails	What you do beforehand
Electricity	Damage to lines or transformers, lack of generation, rolling blackouts.	Power station, batteries, cooling plan (23.6 and 23.7).
Drinking water	The pumps that provide pressure need electricity. In historic winter storms, rolling blackouts shut down water pumping stations; there was low pressure, frozen pipes, and boil-water advisories in entire cities for days.	Stored reserve and purification (23.8 and chapter 3).
Sewer	Sewage pumping stations also use electricity. If they fail, there can be backflow in low-lying areas, and a ground-floor unit is among the first to get it.	Emergency toilet with bags (chapter 21). If the authorities ask you not to flush, don't.
Gasoline	Gas station pumps are electric; in addition, resupply depends on trucks and refineries.	Keep the tank above half. See chapter 9, "Gasoline shortages."
Payments	Card terminals, ATMs, and phone payments need power and internet.	Cash in small bills (23.10, chapter 2).
Food in stores	Supermarkets restock almost daily; without power, without trucks, or with panic buying, the shelves empty quickly.	30-day pantry (chapter 22).
Medicines	Pharmacies closed, prescription systems down, cold chain broken, clinics and dialysis without power.	Reserve, printed list, and plan with your doctor (23.9).
Communications	Cell towers have batteries and some have generators, but they run out and get overloaded.	Battery-powered radio, text messages, contact plan (chapter 19).