Water is the least negotiable line in any emergency plan and the one most often left half-done — because twelve gallons is heavy, bulky, and unglamorous. But nearly every disaster scenario that matters to a household either disrupts water service or makes it unsafe: storm-damaged mains, power loss at treatment and pumping facilities, flood contamination, boil-water notices that follow all three.
This guide covers the two halves of the problem — storing water before, and making water safe after — using the standing guidance from the CDC and Ready.gov as the baseline.
How much: the planning math
The standard figure is one gallon (about four litres) per person per day — half drinking, half sanitation and food prep — with more in hot climates, for pregnant or ill household members, and for physical work. Pets add roughly a quart per day for a mid-size dog, less for cats.
Duration is where location matters. Mainland guidance treats three days as the floor and two weeks as the better target where storage allows. Island and remote households should lean hard toward the high end — as we covered in the typhoon preparedness guide, storm-damaged island water systems can’t draw on neighboring utilities’ repair crews, and restoration can run long. A four-person mainland household targeting three days needs 12 gallons; the same household on a two-week island target needs over 50. That difference should change your container strategy, not your intentions.
Storing water: containers ranked
Commercially bottled water is the easiest correct answer for the drinking half: sealed, regulated, stackable, with a printed date. Stored unopened in a cool dark place, it remains safe long-term — the date is about taste, not safety. Buy it by the case, rotate it through normal use.
Purpose-made water containers — rigid 5–7 gallon jugs or larger stackable bricks, food-grade and opaque — are the workhorses for bulk storage. Before first use, wash and sanitize per CDC instructions (a mild bleach solution, rinsed). Filled from a treated municipal supply, the standing guidance is to replace stored tap water about every six months — pin it to the same calendar sweep as your 72-hour kit check.
Repurposed containers demand care. Two-litre soft drink bottles, properly washed and sanitized, are acceptable per CDC guidance. Milk and juice jugs are not — residual proteins and sugars resist washing and feed bacterial growth — and most are made to biodegrade, weeping at the seams within months. Never use containers that held chemicals.
The bathtub, done right. Filling tubs when a storm approaches is classic island practice — but an unlined tub yields sanitation water (toilet flushing, washing), not drinking water, because tubs and stoppers aren’t food-safe and don’t seal. The upgrade is a purpose-made tub liner (food-grade bladders sized to a bathtub, sold under several brands) which turns the same space into protected potable storage. Either way, a filled tub plus filled pots and coolers meaningfully extends a household’s window.
Store everything off concrete floors (a board or pallet suffices), away from sunlight, fuel, and chemicals.
Making water safe: the field hierarchy
When stored water runs out and supply is questionable, you treat. Know the hierarchy before you need it — it’s also exactly what a boil-water notice assumes you know.
First, clarify. All disinfection methods work poorly on cloudy water. Let it settle, then filter through clean cloth, a coffee filter, or a proper filter until clear.
Boiling is the gold standard. CDC guidance: a rolling boil for one minute (three minutes at elevations above roughly 6,500 feet / 2,000 metres) kills the pathogens of practical concern. Let it cool; pour between clean containers to improve taste.
Plain household bleach when boiling isn’t available. Unscented sodium hypochlorite bleach (the common 5–9% household strength): the CDC’s standing figure is about 8 drops per gallon (roughly 2 drops per litre) of clear water, doubled for cloudy water that can’t be clarified. Stir, wait 30 minutes; a faint chlorine smell is the sign it worked — if there’s none, repeat the dose and wait again. Avoid scented, splashless, or additive bleaches. Bleach also loses strength over time once opened — note the purchase date and rotate the bottle annually.
Purification tablets and portable filters fill the gaps: tablets are compact kit insurance with printed instructions; quality portable filters (the backpacking type) remove bacteria and protozoa but most do not remove viruses — fine for clear backcountry sources, weaker for flood-contaminated supply, where boiling or bleach should follow filtration.
What none of this fixes: chemical contamination. If the concern is fuel, solvents, or a chemical spill rather than microbes, boiling and bleach do nothing — use stored water and official distribution points only, and follow the specific notice from your utility.
The reserves already inside your house
Two water sources exist in most homes before any container is purchased, and both come with conditions.
The water heater. A standard tank water heater holds roughly 30 to 60 gallons of potable water — a meaningful reserve if accessed correctly. The sequence matters: turn off power or gas to the unit first, close the cold-water inlet (which also prevents contaminated mains water from entering during a system failure), let the tank cool, then draw from the bottom drain valve into clean containers. The first draws may carry sediment; let them clear. Tankless heaters hold essentially nothing — households with tankless units should size their stored supply accordingly.
Toilet tanks — with an asterisk. The tank (the upper reservoir, not the bowl) holds a few gallons of the same water that feeds your taps, usable after treatment — unless it contains a drop-in cleaning tablet or colored cleaner, in which case it’s out entirely. The bowl is never drinking water under any circumstances.
One more pre-storm move borrowed from island practice: refrigerators and freezers work as water storage too. Freezing filled bottles ahead of a storm both extends food-safe time during the outage and yields cold drinking water as they thaw — a double dividend covered in our backup power guide discussion of refrigeration.
The household water plan, on one index card
- Cases of bottled water for drinking (rotating through normal use).
- Bulk containers for the balance of the target, refilled every six months.
- Tub liner (or unlined tub for sanitation water) filled at the watch stage of any approaching storm — alongside the rest of the watch-stage actions in your family emergency plan.
- Boil capability that doesn’t need the grid (camp stove, outdoors), plus an eyedropper taped to a bottle of plain unscented bleach with the dosing written on it in marker.
- Know where your utility posts boil-water notices, and follow them exactly — including for ice, coffee makers, pet water, and brushing teeth.
Water planning is tedious precisely because it’s solvable: there are no judgment calls in a gallon. Do the math once, buy the containers once, and the most critical line in your plan stays quietly handled for years.
One last habit closes the loop: when a boil-water notice is lifted, the work isn’t quite over. Standard utility guidance after a lifted notice is to flush the household plumbing — run cold taps for several minutes, dump and remake ice from automatic ice makers, run the dishwasher empty on hot, and replace or flush refrigerator water filters per the manufacturer’s instructions. Contaminated water that sat in lines, tanks, and filters during the notice doesn’t clear itself. Your utility’s lift announcement usually includes the specific flushing steps for your system; follow that version over any generic list, including this one.
FAQ
How much water should a family store for emergencies?
One gallon (about four litres) per person per day — half for drinking, half for sanitation — for a minimum of three days, with two weeks as the better target where storage allows. A family of four targeting two weeks needs over 50 gallons, which usually means bulk containers, not bottle cases alone.
How long can you store tap water in containers?
Standing CDC guidance is to replace stored tap water about every six months, kept in sanitized food-grade containers away from light and heat. Commercially bottled water stored unopened in a cool dark place remains safe past its printed date — the date reflects taste, not safety.
How do you purify water with household bleach?
Use plain, unscented household bleach: about 8 drops per gallon (2 drops per litre) of clear water, doubled for cloudy water. Stir and wait 30 minutes; a slight chlorine odor indicates success. If there’s no odor, repeat the dose once. Never use scented, splashless, or added-cleaner bleach.
Is bathtub water safe to drink in an emergency?
From an unlined tub, treat it as sanitation water — tubs aren’t food-safe and drains leak. With a purpose-made food-grade tub liner filled before the event, the same space becomes legitimate drinking-water storage, commonly 60+ gallons.
Do portable water filters make any water safe?
No. Most portable filters remove bacteria and protozoa but not viruses, and no household filter or disinfection method addresses chemical contamination. For flood-affected or notice-affected municipal supply, boil or chemically disinfect after filtering — and for suspected chemical contamination, use only stored or officially distributed water.