What to Store Water In: Containers, Plastics, and What Leaches
Figures last verified
Water weighs 8.34 pounds per gallon, which sets the practical ceiling on container size at five gallons, or roughly 42 pounds full. Above that a container becomes something you cannot lift, move, or pour from without a pump or a spigot.
The other constraint is what the container is made of and what it previously held. A used juice or soda bottle rinses clean and stores water indefinitely. A used milk jug does not, because milk protein and fat residue remain in the plastic and feed bacterial growth no matter how thoroughly it is washed.
Plastics that work
HDPE, marked with a 2, is the standard for water storage containers, blue five- and seven-gallon jugs, 55-gallon drums, and most purpose-built tanks. It is opaque or translucent, chemically stable, and the blue tint on water-specific containers exists to inhibit algae growth by cutting light.
PETE, marked with a 1, is what soda and juice bottles are made from. It works well for water, is widely available at no cost, and is thinner and more puncture-prone than HDPE. Two-liter soda bottles are the classic free option and are genuinely good.
Polypropylene, marked with a 5, appears in some containers and is suitable.
Avoid PVC, marked 3, and polycarbonate unless specifically sold for potable water. Older polycarbonate is associated with bisphenol A leaching, which is why most current water containers advertise BPA-free construction.
The recycling number alone is not a food-safety designation. It identifies the resin, not what was done with it, which is the same distinction that governs food storage buckets and is covered in food-grade buckets, gamma lids, and what actually seals.
What not to reuse
Milk jugs are the specific case worth naming, since they are the most tempting free container. Milk residue is impossible to fully remove from HDPE, it feeds bacterial growth, and the jugs themselves are made thin for a short shelf life and become brittle and prone to seam failure within a year or two.
Containers that held anything non-food are disqualified permanently. Detergent, solvent, and chemical residues migrate into the plastic and do not wash out, the same problem that rules out construction buckets for food.
Containers that held oily or fatty foods behave like milk jugs. Cooking oil bottles, salad dressing bottles, and similar are not worth the effort.
Juice and soda bottles are fine after a wash with hot soapy water and a thorough rinse. Sugar residue supports growth if left behind, so the rinse matters.
Glass works chemically but breaks, weighs more, and admits light, which makes it a poor choice for volume storage and a reasonable one for small quantities in a dark cupboard.
Container sizes and what each is for
Two-liter bottles hold roughly half a gallon, stack poorly, and are free. Their real advantage is distribution, since a supply broken into small containers can be moved by anyone, kept in multiple rooms, and frozen to buffer a freezer during an outage.
Five-gallon jugs at about 42 pounds full are the standard unit. Most have integrated handles and accept a spigot. This is the largest size an average adult can carry any distance.
Seven-gallon containers at about 58 pounds are the practical upper limit for anything intended to be lifted, and most people find them awkward.
Fifteen- to 30-gallon drums do not get moved once filled and need a pump or a spigot near the bottom. They are storage rather than portable supply.
Fifty-five-gallon drums weigh roughly 460 pounds full. They are a permanent installation, must sit on a floor that can carry the load, and require a siphon pump. They are the cheapest way to store bulk volume and the least useful in an evacuation.
Water bricks and similar stackable rectangular containers cost considerably more per gallon and solve a real problem, since round jugs waste a third of the space they occupy. For closet storage the stacking efficiency can justify the price.
Bathtub bladders are a fill-on-warning product rather than standing storage, holding 60 to 100 gallons, and only useful if you have notice before the water goes out.
Where it goes
Off concrete, always. Concrete transfers cold, holds moisture, and some sources report that plasticizers and concrete chemistry interact over long periods. A pallet, a shelf, or a sheet of plywood resolves it.
Out of light. Algae needs light and water and will grow in a clear container on a sunny shelf. Opaque containers or dark storage solve it.
Away from fuel, pesticides, and solvents. Plastic is gas-permeable enough that vapors from a nearby gasoline can will eventually be detectable in stored water. This is a real and frequently observed failure, not a theoretical one.
Cool and stable. Heat accelerates plastic degradation and any biological activity present.
Weight matters structurally. Sixty gallons is about 500 pounds concentrated in a small footprint, which is fine on a slab and worth thinking about on a second floor or an old joist system.
Filling and sealing
Wash the container with hot soapy water, rinse thoroughly, and sanitize with a dilute bleach solution if it is not new, swirling it to contact every interior surface and rinsing after.
Fill from the tap. Municipal water arrives chlorinated and needs nothing added. Well water and untreated sources need treatment before storage, and dosing depends on bleach concentration rather than on the numbers most charts quote, covered in how much bleach per gallon.
Fill to the top to minimize trapped air, and cap tightly.
Label with the fill date. Not an expiry date, since stored municipal water does not expire on a schedule, for reasons in does stored water go bad.
Leave headspace only if the container may freeze, since water expands and will split a full rigid container.
Spigots, pumps, and getting it out
A five-gallon jug without a spigot is poured, which requires lifting 42 pounds to a height and is awkward enough that people avoid doing it. A cheap spigot converts the same container into something a child can use.
Drums need a siphon pump, and the pump should be bought and tested at the same time as the drum rather than assumed.
A short length of food-grade tubing is the fallback for any container, and siphoning works from any container higher than the receiving vessel.
How much to buy
The volume follows from the per-person figure and the planning horizon, and both are more contested than they appear, which is worked through in where the one-gallon-per-person-per-day number comes from. For most households the answer lands near 60 gallons of stored water once the water heater is counted as part of the supply, and what that supply consists of is in the water already in your house.