Stored litres are only useful when their quality, access method and intended uses are clear before the outage begins.
1. Separate potable water from service water
List drinking, cooking and oral-hygiene water separately from toilet flushing, cleaning, irrigation and other service uses. Assign each use a source that remains available in the scenario.
Do not assume rainwater, a cistern or water left in plumbing is safe to drink. Potable storage, containers and treatment need their own documented plan.
2. Set an essential daily volume
Build the household estimate from people, animals and essential tasks, then multiply by the outage duration. Add an explicit reserve instead of hiding uncertainty inside the daily number.
As an emergency baseline, CDC advises storing at least one gallon of water per person per day for three days and notes that more may be needed for health, climate, pregnancy, pets or other circumstances. Adapt official local guidance to your household.
CDC · Create and store an emergency water supply ↗3. Trace every electrical dependency
A private well may depend on the submersible pump, pressure controls, treatment equipment, heat tracing and sometimes a booster pump. Record both starting power and daily energy for the equipment that must operate.
Decide whether stored water can be reached by gravity or a small backup pump. Confirm valves, backflow protection and the method for isolating any source whose quality is uncertain.
4. Protect water quality during and after the event
Keep emergency drinking water in suitable, clearly labelled containers and follow the storage and replacement instructions for the chosen method. Avoid cross-connecting potable plumbing with an untreated source.
Flooding or damage can contaminate a private well. EPA advises avoiding use of a flooded well for drinking or washing and seeking inspection, cleaning, disinfection and testing guidance before returning it to service.
EPA · Protect your home's water after an emergency ↗5. Run a short household drill
Turn off the normal supply only under safe conditions and walk through one representative day. Check whether people can reach, measure and carry the planned water and whether sanitation still works.
Record actual consumption, pump energy, container handling and any confusing valves or instructions. Update labels and the calculation while the experience is fresh.
A useful outage worksheet
| Question | Record | Why it matters |
|---|---|---|
| Who and what needs water? | People, pets, essential tasks | Sets daily demand |
| Which water must be potable? | Drinking, cooking, oral hygiene | Sets quality controls |
| What stops without power? | Pumps, controls, treatment | Sets backup-power loads |
| How is stored water reached? | Gravity, tap or backup pump | Tests practical access |
| When is normal service safe? | Inspection or advisory criteria | Prevents premature reuse |
Worked example
Four-day essential-water scenario
A household plans to use 60 L/day from a tank for four days and protects 20% of the starting volume as reserve.
Required usable water = 60 × 4 = 240 L Starting storage = 240 / (1 − 0.20) = 300 L
The 300 L tank scenario covers the stated service-water demand only. Potable quality, containers, access and a longer outage remain separate checks.
What to have ready
- People, pets and essential water uses
- Separate potable and service-water sources
- Usable storage, reserve and access method
- Pump and treatment power requirements
- Safe return-to-service criteria
Common mistakes
- Counting total tank volume as usable water.
- Treating clear water as proof that it is safe to drink.
- Backing up a well pump but forgetting controls or treatment equipment.
Reference check: 5 September 2026. Sources include US public agencies. Principles are general; regulations and design values must be checked where you live.Worked examples use stated hypothetical inputs.