Water is the supply most households underestimate. It’s heavy, it takes space, and unlike canned food, the quantity required to cover even a short emergency is genuinely substantial. For a family of four, three days of water at the standard planning figure is twelve gallons — and that’s before accounting for pets, hygiene beyond bare minimum, or the possibility that three days turns into five.

This guide covers the practical decisions: how much to store, what to store it in, how long it lasts, and when stored water needs treatment before use.

How much water to store

The standard planning figure — used by Ready.gov, the American Red Cross, and most state emergency management agencies — is one gallon per person per day, divided roughly half for drinking and half for sanitation and food preparation. Three days is the basic floor most agencies recommend.

A few adjustments to the one-gallon figure that commonly apply:

  • Hot climates and physical activity. Drinking needs increase meaningfully in heat or with physical exertion. If you’d be active during an emergency (clearing debris, caring for animals), plan more.
  • Infants. Formula preparation adds water use. If an infant in the household is formula-fed, add at least one extra gallon per day.
  • Pets. Dogs and cats need water too. A medium-sized dog needs roughly half a gallon per day; cats need less but still need fresh water. Don’t forget this in the calculation.
  • Island and remote communities. Households in areas where relief arrives slowly — Pacific islands, rural communities, areas accessible by a single road that can flood — should extend beyond 72 hours. A week of water for the household is not excessive if resupply is genuinely slow.

Container options

Commercial bottled water

The simplest option: sealed, regulated by the FDA, date-stamped, and stable in a cool, dark location. The downside is cost relative to tap water and the ongoing plastic use. If you’re starting from nothing, buying enough 1-gallon or multi-gallon jugs to cover the household baseline is the fastest way to build a supply.

Food-grade water storage containers

Purpose-built food-grade plastic containers — 5-gallon, 7-gallon, and larger — are sold through emergency preparedness and outdoor retailers. They’re the workhorse of home water storage. Key considerations:

  • Food-grade only. Do not repurpose containers that held milk, juice, or non-food products. Milk proteins are difficult to remove completely and can support bacterial growth. Clear water bottles and food-grade containers labeled with the recycling code 2 (HDPE) or 1 (PET) are appropriate.
  • Fill from the tap. Municipal tap water in the United States is treated with chlorine or chloramine — you generally do not need to add additional treatment before storing it in a clean container. If your water comes from a well or private source without disinfection, treatment before storage is recommended.
  • Keep out of direct sunlight and away from heat. Both promote algae growth and accelerate container degradation.

55-gallon drums

For households that want substantial storage — a week or more for a family — 55-gallon food-grade polyethylene drums are a cost-effective option. They require a pump or siphon to retrieve water and take significant floor space, but they hold enough water that topping up periodically rather than frequent full rotations becomes practical. Garages, basements (above flood level), and shaded outdoor areas work for storage.

Bathtub liners (WaterBOB type)

Plastic liners designed to sit in a standard bathtub and fill from the tap can store 65–100 gallons of water when deployed in advance of a storm or outage. They’re single-use, inexpensive, and only work if deployed before the event — you can’t fill them from the tap after the water supply fails. They’re a good complement to, not a replacement for, standing stored water.

How long does stored water last?

Commercially bottled water carries manufacturer “best by” dates, but water itself doesn’t expire — properly sealed commercial water can last much longer. The dates reflect quality under typical storage conditions: light exposure, heat, and container degradation can cause off-flavors. Water stored correctly (cool, dark, sealed) is safe well beyond the printed date.

Tap water stored at home in clean food-grade containers is typically recommended for rotation every six to twelve months. This isn’t because the water becomes unsafe in that timeframe (municipal-treated water retains residual disinfectant for weeks, and in a sealed clean container, contamination risk is low), but because it’s good practice to taste-test your supply and maintain the rotation habit. Mark every container with the fill date.

Water that has been opened and partially used should be consumed relatively quickly — within a few days — just as you’d treat any opened container in normal use.

Treating stored water: when and how

From municipal treated sources: you generally do not need to add treatment before storing tap water in a clean container. The disinfectant residual in municipal water will persist during storage, and a properly cleaned and sealed container introduces minimal contamination risk.

From untreated sources (wells, surface water, collected rainwater): treatment is required before storage. Options:

  • Boiling: a rolling boil for one minute (three minutes above 6,500 feet elevation) kills biological contaminants. This is the CDC and EPA recommendation for microbiologically uncertain water. It doesn’t remove chemical contaminants.
  • Unscented liquid chlorine bleach: CDC guidance is to add 8 drops (about 1/8 teaspoon) of unscented household bleach with 6–8.25% sodium hypochlorite to one gallon of water, stir, and let stand for 30 minutes before use. If the water is cloudy, filter it first (a coffee filter or clean cloth removes particles) and double the bleach quantity.
  • Water purification tablets: iodine or sodium dichloroisocyanurate tablets are available from outdoor retailers. Follow manufacturer dosing instructions.
  • Portable filters: filter devices (ceramic filters, hollow-fiber membrane filters like those in backpacking equipment) remove biological contaminants but generally do not inactivate viruses; they work well for natural surface water in a domestic context.

The practical storage setup for most households

A realistic baseline for a family of four:

  • Twelve 1-gallon jugs or three 4-gallon containers = 72-hour supply. Store in a hall closet near the exit, above any flood level.
  • One 5- or 7-gallon container refilled every six months from the tap as the emergency backup.
  • A WaterBOB liner in the disaster kit to deploy before any predicted event, buying an additional 65–100 gallons from the tap when there’s warning.

The total cost of a functional water supply for a four-person household is generally under $50, with the ongoing cost of periodic rotation and occasional container replacement. For the risk it addresses — the single most urgent supply in any extended emergency — that cost-to-benefit ratio is unusually favorable.

FAQ

Does stored water expire?

Commercially bottled water carries a “best by” date, but properly stored water doesn’t become unsafe past that date — it may develop off-tastes from container degradation or absorbed odors. Home-stored tap water in food-grade containers should be rotated every six to twelve months as a quality habit, not because it becomes dangerous.

Can I store water in old milk jugs?

It’s not recommended. Milk jugs are difficult to clean thoroughly enough to remove milk proteins, which can support bacterial growth. Use containers designed and labeled for water or food storage.

Should I add bleach to tap water before storing it?

If your water comes from a treated municipal supply, generally no — the disinfectant residual from treatment will persist in storage. If your source is untreated (a well or surface water), treat before storing.

How much water does a pet need in an emergency?

Roughly: small dogs 1/4 gallon per day; medium dogs 1/2 gallon; large dogs up to 1 gallon. Cats need less but still need fresh water daily. Include pets in your per-day calculation before you decide how much to store.

What if I run out of stored water during an extended emergency?

Treatment first, then consumption. Boiling (one full minute rolling boil) is the most reliable treatment for water from taps that may be compromised, rainwater, or any natural surface source. Have a backup fuel source — a camp stove, a propane burner — that allows boiling if the grid is down.