Bathtub Emergency Water Storage: The WaterBOB and DIY Methods

When a hurricane, ice storm, or boil-water advisory is forecast, your bathtub is the single biggest water container you already own. A standard tub can hold close to 100 gallons — enough to carry a family through days of an outage. The catch is timing: this only works if you fill it before the event, while the taps still run clean.

For urban preppers and renters, this is one of the highest-value moves you can make. You don't need a basement, a garage, or a row of barrels. You need a clean tub, a few minutes of warning, and ideally a food-grade liner so the water you store is actually drinkable instead of merely useful for flushing.

This guide covers when to fill, how the WaterBOB liner works, the bare-tub DIY method and its real limitations, how much water you actually need, and exactly how to purify what you store so it's safe to drink.

Fill the Tub Before the Storm — Not After

The most important rule of bathtub water storage is about timing, and it is the one people most often get wrong. You fill the tub before the event reaches you, while municipal water is still flowing and still clean.

Once a boil-water advisory is issued, the water coming out of your tap may already be contaminated — storing it just means storing the problem. Once the grid goes down, pumps that maintain water pressure can fail, and your taps may slow to a trickle or stop entirely. By the time you realize you need water, the window to collect clean water has usually closed.

So treat the forecast as your trigger. When a hurricane, winter storm, wildfire-driven outage, or planned utility shutoff is on the way, fill your storage early — a day ahead is not too soon. If you live in an apartment where outages can knock out the building's water pressure, the same logic applies to any extended blackout. For the broader playbook on getting through a contamination event in a city home, see our guide on a boil-water advisory in an apartment.

The WaterBOB: Clean, Drinkable Tub Storage

A bare bathtub is not a great drinking-water container — but a WaterBOB turns it into one. The WaterBOB is a large, food-grade plastic liner that sits inside your tub and holds about 100 gallons of water sealed away from the tub surface, dust, and contaminants.

Using it is simple. You spread the empty liner across a clean tub, connect the included fill tube to your bathtub faucet, and run the water. As it fills, the liner expands to take the shape of the tub. Because the water never touches the tub itself and stays sealed inside food-grade plastic, it stays clean and drinkable for weeks rather than hours.

The kit includes a hand siphon pump so you can draw water out a few cups or quarts at a time without opening the whole thing or dunking a dirty container into your supply. That single detail is what makes it genuinely sanitary: your stored water stays sealed and protected right up until the moment you use each portion.

• Food-grade and BPA-free: the plastic is rated for drinking water, unlike a tub surface.
• Sealed from contamination: dust, pet hair, and stray cleaning residue never reach the water.
• Siphon pump included: draw clean portions without contaminating the rest.
• Single-use per storm: most people treat one liner as a per-event item; keep a spare or two on hand.

It packs flat to the size of a thin envelope, so storing a couple of them in a linen closet costs you almost no space. For renters and urban preppers without dedicated water storage, it's the closest thing to a no-compromise solution. Pair it with the rest of your supply strategy in our guide to water storage with no basement.

The DIY Bare-Tub Method (and Its Big Caveat)

If a storm is hours away and you don't own a liner, you can still use the tub directly — but go in with clear eyes about what that water is and isn't good for.

The caveat is the whole point: a bathtub is not food-safe. Tub surfaces hold soap scum, cleaning-product residue, and bacteria in the drain and overflow, and the materials themselves aren't certified for drinking-water contact. On top of that, most tub drains leak slowly, so a bare tub will lose water over hours to days. For these reasons, treat bare-tub water as non-potable by default — best reserved for flushing toilets, washing, and cleaning.

How to Do It Right

• Clean the tub first. Scrub it, rinse thoroughly to remove all cleaner residue, then wipe it down. Skipping this step contaminates every gallon.
• Reduce the drain leak. A flat rubber stopper seals better than the built-in drain. Some people add a layer of plastic wrap under the stopper to slow seepage.
• Cover it. Lay a clean sheet or plastic over the top to keep dust, pets, and debris out.
• Use it for sanitation first. Reserve bottled or liner-stored water for drinking; use the tub for the toilet and washing.
• Purify before drinking. If the bare tub becomes your only source, you must purify it before it's safe to drink — see the next section.

How Much Water Per Person Do You Need?

The Red Cross and FEMA both recommend a minimum of one gallon of water per person per day — roughly half for drinking and half for cooking and basic hygiene. That's a floor, not a comfortable target. In hot weather, or if anyone in your household is pregnant, ill, or very active, plan for more. Don't forget pets: a medium dog needs about half a gallon a day.

Here's why the tub matters so much. At one gallon per person per day, a 100-gallon WaterBOB covers:

• One person: about 3 months of bare-minimum water.
• A family of four: about 3 weeks of drinking and basic needs.
• A family of four, drinking only: well over a month, if the tub water is used for sanitation and bottled water for drinking.

Storage method	Capacity	Drinkable?	Covers (1 gal/person/day)
WaterBOB liner	~100 gallons	Yes — food-grade, sealed	1 person ~3 months; family of four ~3 weeks
Bare bathtub	40–80 gallons	No — purify first; best for sanitation	Days of flushing and washing for a household
WaterBrick (3.5 gal each)	~21 gallons per 6-pack	Yes — fill and rotate now	1 person ~3 weeks per 6-pack

A bare tub holds less — typically 40 to 80 gallons depending on its size and how well you slow the drain leak — but even at the low end, that's days of flushing and washing that you'd otherwise spend hauling water. The standard guidance is to keep a two-week supply at home where you can; the tub is how city dwellers without storage space hit that number on short notice. For day-to-day storage you can rotate, see our breakdown of small-space water storage options.

Purifying Stored Tub Water — Be Precise

If your stored water came from a bare tub, sat for a long time, or you simply aren't certain it's clean, purify it before drinking. There are two reliable household methods. Follow the ratios exactly.

Boiling (the most reliable method)

Per the CDC, bring the water to a rolling boil and hold it there for one full minute. At elevations above 6,500 feet (roughly 2,000 meters), boil for three minutes because water boils at a lower temperature. Let it cool naturally — never add ice to speed it up. If the water looks cloudy, let it settle and filter it through a clean cloth or coffee filter first. Boiling kills bacteria, viruses, and parasites, but it does not remove chemical contamination.

Bleach (when you can't boil)

Use plain, unscented household bleach (5% to 9% sodium hypochlorite) with no added cleaners, scents, or color-safe additives. Following EPA guidance:

• Clear water: add 8 drops (about ⅛ teaspoon) of 6% bleach per gallon. If your bleach is the older 5.25–6% strength, the same 8 drops per gallon applies; for 8.25% bleach use 6 drops per gallon.
• Cloudy water: double the dose to 16 drops per gallon — and filter it first if you can.
• Then wait: stir, and let it stand for 30 minutes. The water should have a slight chlorine smell. If it doesn't, repeat the dose and wait another 15 minutes. If it still has no chlorine odor, discard it and find another source.

Purification tablets are a convenient backup that store for years and weigh nothing. Chlorine dioxide tablets, in particular, handle a broader range of organisms than basic iodine. Keep a bottle with your kit. You can compare options with a quick search for water purification tablets on Amazon.

The Gear That Makes Tub Storage Work

You don't need much — and most of it stores flat. This is the short list that turns "I have a tub" into "I have a clean, drinkable emergency water supply."

No Tub? Your Alternatives

Plenty of urban homes have only a shower stall, or a tub you'd rather not take out of service. You still have good options — they just take a little more forethought because they're not last-minute fills.

• Stackable water containers: rigid 3.5- to 5-gallon jugs (like WaterBricks) stack in a closet and rotate easily. Fill them now, not during the storm.
• Collapsible water jugs: 5-gallon soft containers fold flat when empty and fill fast at the tap. Cheap, light, and easy to stash several.
• Food-grade 5- to 7-gallon carriers: the classic blue camping jugs; durable and easy to pour.
• A clean trash can with a liner: a fresh, heavy-duty food-grade liner inside a clean bin can hold 20 to 40 gallons in a pinch — purify before drinking.
• Top off everything you own: pots, pitchers, clean drink dispensers, and sealable jugs all add up when a storm is hours out.

However you store it, the principle is identical to the tub: collect clean water early, keep it covered, and purify anything you're unsure about before you drink it. For a complete plan that doesn't depend on a basement or a bathtub, read our guide to storing water with no basement.