The 72-Hour Water Rule: How much you actually need.

When municipal water is contaminated or the power grid goes down, grocery store shelves empty within 2 hours. One gallon per person per day is the biological baseline.

SNTU field manual diagram illustrating 72-hour emergency water storage calculation for a family of four

EMERGENCY BASELINE: 1 GALLON PER PERSON PER DAY • 3 DAYS MINIMUM = 12 GALLONS FOR A FAMILY OF 4

SECTION 01THE BASICS

WHAT IS THIS?

In a boil-water advisory, hurricane, freeze, or water main rupture, your taps will either stop flowing or deliver contaminated water.

Humans can survive weeks without food, but only 3 days without clean water. Half of your emergency water is for drinking; the other half is for food preparation and basic sanitary hygiene.

SECTION 02RISK & COST

WHY SHOULD I CARE?

Panic-buying water during a storm warning is chaotic and often impossible. Water is heavy, bulky, and impossible to download when the municipal pumps lose pressure.

Dehydration reduces cognitive decision-making within 24 hours, making emergency response much more hazardous.

SECTION 03FIELD PROTOCOL

WHAT SHOULD I DO?

Store 1 gallon per person per day for at least 3 days. For a family of 3, that is 9 gallons stored in food-grade containers in a dark, cool space.

Calculate family headcount

People + pets (don't forget 1 gallon per large pet).

Purchase food-grade storage

Use commercially bottled water or heavy-duty food-grade HDPE 5-gallon jugs (WaterBrick or Reliance).

Rotate annually

Mark the date of purchase on the container with a marker and rotate each year.

WHAT TO DO NEXT

ACTION RULE

YOUR 5-MINUTE CHECKLIST:

Count household members including pets.
Store at least 3 days of water in a cool closet or garage corner.
Have a mechanical water filter (e.g. Sawyer Squeeze) as backup.

DECISION RULE:

“Never wait for a storm warning to buy water. Keep your 72-hour baseline permanently stocked.”

SOURCES & REGULATORY REFERENCES:

•Emergency Water Supply and Storage Recommendations(Federal Emergency Management Agency (FEMA) & CDC)

FIELD GUIDE / 001

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