Water Storage Containers: Which Materials Are Food Grade and Safe for Drinking Water

Most people buy water storage containers on price and color. Then they store them in a hot garage, in direct sun, on a concrete slab, and wonder six months later why the water tastes like the container.

The container is the part of your water plan you cannot fix later. You can filter dirty water. You can boil it. You cannot un-leach a plastic. And the labels that are supposed to help you (food grade, BPA free, NSF certified) each mean something specific and narrow, and none of them mean all of it.

So here is what each of those terms actually covers, which materials hold up, which ones are a hard no, and what temperature does to the whole equation.

What does "food grade" actually mean for water storage containers?

It means the material is cleared for food contact under FDA rules that are built around migration, which is the amount of the container that ends up in what it holds. FDA defines a food contact substance as "a substance that comes into contact with food and is not intended to have a technical effect in such food," and requires premarket authorization through its Food Contact Notification program.

What that review actually looks at is worth knowing, because it tells you what the label is promising:

• Testing data showing how much of the substance migrates into food under the intended conditions of use.

• Toxicological data showing that the resulting consumer exposure is safe.

• An environmental review under NEPA.

FDA publishes a public inventory of every food contact substance authorized through that program. The part most guides skip is the phrase "under the intended conditions of use." A resin cleared for cold liquids at room temperature was not evaluated for 140 degrees F in a July attic. The clearance is a package deal with the conditions, and if you change the conditions, you are outside what was tested. Keep that in mind for the temperature section below.

One more thing "food grade" does not mean: it says nothing about the container's previous contents. That is a separate question, and it has a much shorter answer.

What do the recycling numbers on the bottom mean?

They identify the resin, and nothing more. The triangle with a number is a resin identification code. It tells a recycling sorter what polymer it is looking at. It is not a safety rating, it is not an FDA mark, and a high number is not worse than a low one.

For water storage, four of them come up:

• 1, PET or PETE. Clear, strong, light. The material of most single use water and soda bottles.

• 2, HDPE. Opaque, stiff, chemically boring. The material of milk jugs, most blue water barrels, and most 5 to 7 gallon water containers.

• 5, PP or polypropylene. Higher heat tolerance, common in lids and some tanks.

• 7, other. A catch all. Polycarbonate lives here, and so does a lot of unrelated material. A 7 tells you almost nothing by itself.

The part most guides skip is that the same resin code can be food grade or not. HDPE used for a chemical drum is the same polymer as HDPE used for a water barrel, but the colorants, mold release agents, and regrind content can differ, and those are exactly the things food contact clearance covers. The code tells you the family. The manufacturer's food contact statement tells you whether this specific part was made for the job.

Why is HDPE the standard for water storage containers?

Because it needs almost nothing added to it to work. HDPE is stiff on its own, so it does not need plasticizers, which are the additives most likely to migrate out of flexible plastics. It is naturally opaque, which keeps light out. It handles freeze and thaw without cracking as readily as rigid clear plastics. And it is cheap enough to buy in the sizes that matter.

That combination is why University of Arizona Cooperative Extension lists extruded white, black, and green polyethylene among the standard above ground storage tank materials, alongside welded galvanized steel and fiberglass.

Practical HDPE notes:

• Buy it opaque. Translucent tanks let you see the water level, but Arizona Extension warns that "the translucent material of these tanks will also allow sunlight to penetrate and can facilitate the growth of algae inside the tank."

• Do not confuse a food grade HDPE drum with a reconditioned industrial one. Same resin family, completely different history.

• Plastic is permeable. Utah State University Extension notes that plastic is permeable to certain vapors and says to keep stored water away from gasoline, kerosene, and pesticides. This is the real reason not to store water next to the lawn mower gas can.

Is PET safe for long term water storage?

Yes at normal indoor temperatures, and no in the heat, and there are numbers behind that. PET releases small amounts of antimony, which is used as a catalyst in making the resin. EPA's maximum contaminant level for antimony in drinking water is 0.006 mg/L, which is 6 parts per billion.

A study published in the Journal of Environmental Health Science and Engineering tracked antimony in bottled water across five storage conditions:

• Room temperature, about 77 degrees F: antimony started at roughly 1.01 ppb and reached 2.54 ppb after 8 weeks. Still well under the 6 ppb limit.

• 104 degrees F for 8 weeks: still under the limit.

• Outdoor storage averaging about 88 degrees F for 8 weeks: still under the limit.

• 149 degrees F: exceeded the limit after 2 weeks for the samples that started highest.

• 176 degrees F: exceeded the limit in 2 to 3 days.

The lesson is not "PET is bad." The lesson is that migration is a temperature curve, and the top of that curve is reachable in a closed car, a metal shed, or an attic in August. This is why CDC's storage guidance specifies a location between 50 and 70 degrees F, away from direct sunlight. Temperature is doing more work in that sentence than most people realize.

What about polycarbonate and BPA?

Polycarbonate is the hard, clear, glass-like plastic used in older 5 gallon office water jugs and some camping bottles, and it is made using bisphenol A. FDA's current position, based on a four year review of more than 300 studies completed in 2014, is that "BPA is safe at the current levels occurring in foods."

Two clarifications that get garbled constantly. FDA did revoke its authorization for BPA based polycarbonate in baby bottles and sippy cups in July 2012, and for BPA based epoxy coatings in infant formula packaging in July 2013. But FDA is explicit that those amendments were "not based on safety" and were made because industry had permanently abandoned those uses.

The practical reason to skip polycarbonate for long term water storage is not the BPA argument at all. It is that it is clear, expensive, and brittle compared to HDPE, and clear is the wrong property for water you intend to leave alone. If you want the durability, buy stainless. If you want the price, buy HDPE.

Can you reuse a container that held something else?

Not if it held a non food product. This is the one rule in this whole article with no nuance in it. CDC is direct: "Do not use containers that were previously used to hold liquid or solid toxic chemicals, such as bleach or pesticides."

The reason is the permeability point from earlier. Plastic is not a wall, it is a sponge with very small pores. Solvents, pesticides, and surfactants absorb into the polymer, and no amount of washing pulls them back out. A drum that held detergent will keep releasing detergent into water for years.

Containers that previously held food are a different question, with two real answers:

• Soda and juice bottles are fine. Oregon State University Extension specifically lists "plastic soda bottles, juice bottles and water jugs with screw-on lids" as suitable, along with camping water carriers.

• Milk jugs are not. Oregon State Extension says milk containers "are not recommended for long term storage because they are made from a biodegradable plastic." They are also nearly impossible to clean of milk protein, which is what actually spoils the water.

Whatever you reuse, sanitize it. CDC's procedure is specific: wash with soap and rinse, then mix 1 teaspoon of unscented liquid household chlorine bleach (5 to 9 percent sodium hypochlorite) into 1 quart of water, cover and shake so the solution touches every interior surface, wait at least 30 seconds, empty, and air dry completely before filling.

Which metals work for drinking water, and which ones do not?

Stainless steel works. Almost everything else needs a liner or a coating. Utah State Extension puts it plainly: stainless steel has been used successfully, and "other metals are not optimal containers unless they are coated and made specifically to hold food or water," with pewter and lead soldered metals to be avoided outright.

Galvanized steel is the one people get wrong, because galvanized buckets and stock tanks are everywhere and they look clean. Galvanizing is a zinc coating over steel, and EPA lists "corrosion of galvanized pipes" as a source of cadmium in drinking water, with a maximum contaminant level of 0.005 mg/L and kidney damage as the health effect. Zinc coatings historically carry cadmium and lead as impurities.

That does not mean galvanized tanks are unusable, it means they need a barrier. The Texas Manual on Rainwater Harvesting, published by the Texas Water Development Board, says galvanized steel tanks "can be lined for potable use," typically with a food grade polyethylene or PVC liner, or coated inside with epoxy paint that "must be FDA- and NSF-approved for potability."

On lead, there is a bright legal line worth knowing. Under the Safe Drinking Water Act, "lead free" means a weighted average of 0.25 percent lead across the wetted surfaces of pipes, fittings, and fixtures, and 0.2 percent for solder and flux. Since September 1, 2023, manufacturers must certify compliance through a consistent verification process. If you are adding a spigot, valve, or fill hose to a water storage setup, that is the spec to look for.

What is NSF/ANSI 61, and does it apply to my containers?

NSF/ANSI/CAN 61 sets health effects limits for what leaches out of drinking water system components. NSF describes it as establishing "minimum health-effects requirements for the chemical contaminants and impurities that are indirectly imparted to drinking water from products, components and materials used in drinking water systems."

It covers pipes and fittings, gaskets and adhesives, coatings and cements, valves and meters, filter media, and nonmetallic potable water materials. In practice, on a home water storage setup, it is most relevant to the hardware: the spigot, the hose you fill from, the tank coating, the bulkhead fitting.

The part most guides skip is what NSF/ANSI 61 explicitly does not do. Per NSF, the standard "does not establish performance, taste and odor, or microbial growth support requirements." So a certified component will not poison your water, but the certification is not a promise the water will taste good or stay biologically clean. That is on your storage conditions and your rotation, not on the mark.

Why are water storage containers blue, and does sunlight matter?

Blue is a convention that signals potable water, but the property doing the work is opacity, not the color. Light drives algae growth, and algae is the most common reason stored water goes green and starts tasting like a pond.

Both the Texas Water Development Board and Arizona Extension are blunt about this. The Texas manual states that "storage tanks must be opaque, either upon purchase or painted later, to inhibit algae growth." Arizona Extension warns that translucent tank walls let sunlight through and facilitate algae growth inside the tank.

What that means for how you store containers:

• Opaque beats clear for anything you are not going to look at for months.

• Keep containers out of direct sun, both for algae and because UV embrittles plastic over time.

• Utah State Extension says to store water "in a clean, dry place off the ground and away from sunlight." Off the ground is not superstition. It keeps the container off cold, damp concrete and makes leaks visible before they become puddles.

• Oregon State adds a location rule that catches people out: store containers away from cleaning supplies, fertilizer, and other products with strong odors.

What about concrete and fiberglass cisterns?

Both work for potable water, and both need the right interior. This is where large scale storage differs from jugs on a shelf, because a tank this size usually exists to hold a supply that refills itself, most often rainwater collected off a roof. The Texas Water Development Board's manual lays out the trade offs:

• Fiberglass. Available from 50 to 15,000 gallons. For potable use, tanks "should have a USDA-approved food-grade resin lining." Durable and weather resistant with integrated fittings.

• Concrete. Poured in place or prefabricated. It "may be prone to cracking and leaking, especially in underground tanks in clay soil." For potable systems, "it is essential that the interior of the tank be plastered with a high-quality material approved for potable use." Interestingly, the manual notes a possible upside: calcium dissolving out of the concrete into slightly acidic rainwater can improve the taste.

• Polypropylene. 50 to 10,000 gallons and relatively inexpensive, but it "does not retain paint well, so it is necessary to find off-the-shelf tanks manufactured with opaque plastic."

• Wood and ferrocement. Both require a food grade liner or an approved interior finish for potable use.

The pattern across every one of those materials is the same. What matters is not the shell, it is the surface actually touching the water, and whether that surface was approved for potable contact.

How does container choice change rotation and disinfection?

Material determines what you can do to clean it, and how visible problems will be. That changes your maintenance routine more than most people expect. For anything too big to dump and refill, testing the water quality in the tank on a schedule is how you know where you stand.

• Small food grade plastic containers. CDC says to replace stored water every 6 months, and Utah State Extension says to check containers every 6 to 12 months for secure lids, cracks, and cloudiness. Small containers are easy to dump, scrub, and refill, so rotation is cheap.

• Stainless steel. Handles hot water and boiling, tolerates aggressive scrubbing, and does not scratch into a haven for biofilm the way soft plastic does. It also costs several times more per gallon.

• Large tanks and cisterns. You do not rotate these, you disinfect them in place. Arizona Extension's method for a small tank is 1 to 2 quarts of fresh, unopened household bleach per 1,000 gallons, which produces roughly 13 to 26 ppm free chlorine, held for 12 to 24 hours. For maintaining a residual, they cite 0.2 to 1.5 ppm, measured with a DPD-1 test method rather than an OTO pool kit, which reads total chlorine instead of free chlorine.

The part most guides skip is that a scratched plastic container is a different container than the one you bought. Scratches and scuffs on the inside wall create surface area and shelter that free chlorine has trouble reaching. If you are going to store water for years in one vessel, buy something you can inspect and scrub without gouging, and label every container "drinking water" with the date, which is CDC's instruction and the only reliable way to know what you are looking at three years from now. The container also sets the outside edge of how long you can store water safely before it needs rotating.

When to get professional help

Most water storage is a homeowner job. A few situations are not.

• You are connecting storage to household plumbing. Any tank plumbed into a supply line raises cross connection and backflow issues. That is a licensed plumber's work, and often a permit.

• You inherited a tank and do not know its history. If you cannot document what a used tank held, do not use it for drinking water. Use it for irrigation and buy a new one for potable storage.

• Your stored water tastes metallic, smells chemical, or has visible growth. Do not drink it. Empty it, and if the problem recurs in a clean container, have the source water tested through your state certified lab or local health department.

• Someone swallows household bleach or a cleaning product while sanitizing containers. Call Poison Control at 1-800-222-1222, free and staffed 24 hours. If the person is unconscious, seizing, or not breathing, call 911 instead.

• You have an infant, someone pregnant, or someone immunocompromised in the house. Talk to your doctor or local health department before relying on long stored water, and ask about testing.

Frequently asked questions

What is the best material for water storage containers?

Food grade HDPE for most people, and stainless steel if you want a container that lasts decades and tolerates boiling. HDPE is opaque, tough, needs no plasticizers, and is cheap enough to buy in useful sizes. Stainless costs more per gallon but resists scratching and biofilm. Both should be stored cool, dark, and off the floor.

How can you tell if a container is food grade?

Check the manufacturer's food contact statement, not the resin code. The recycling triangle only identifies the polymer. FDA reviews food contact substances for how much migrates into food under intended conditions of use, and maintains a public inventory of authorized substances. If a seller cannot tell you the container was made for food or water contact, treat it as not.

Can you store drinking water in a galvanized container?

Not unlined. EPA lists corrosion of galvanized pipes as a source of cadmium in drinking water, with a maximum contaminant level of 0.005 mg/L and kidney damage as the health effect. Galvanized tanks can be used for potable water when they are fitted with a food grade polyethylene or PVC liner or coated inside with epoxy that is FDA and NSF approved for potability.

Does heat ruin water stored in plastic bottles?

Heat is the single biggest factor in what leaches out. Published testing found antimony in PET bottled water stayed under EPA's 6 ppb limit at room temperature and at 104 degrees F for 8 weeks, but exceeded it after 2 weeks at 149 degrees F and within 2 to 3 days at 176 degrees F. CDC recommends storing water at 50 to 70 degrees F, out of direct sunlight. A hot car or attic is the worst place you can pick.

Is BPA free plastic necessary for water storage containers?

It is not the deciding factor. FDA's position, after a four year review of more than 300 studies, is that BPA is safe at current levels in food, and its revocations of BPA in baby bottles and infant formula packaging were based on abandoned use rather than safety findings. Most water storage containers are HDPE, which does not use BPA at all, so the question rarely comes up outside of clear polycarbonate jugs.

Why should water containers be stored off the concrete floor?

Utah State Extension recommends storing water off the ground and away from sunlight. Raising containers on a pallet or shelf keeps them off cold damp concrete, lets air move around them, and makes a slow leak visible before it becomes a problem. It also gets containers away from floor level fumes, which matters because plastic is permeable to vapors from gasoline, kerosene, and pesticides.

Container choice is a decision you only get to make once per container, so it is worth ten extra minutes and a few extra dollars. Food grade material, opaque walls, a lid that actually seals, and a cool dark spot off the floor covers most of it.

Everything else is maintenance you can adjust later. Label them, date them, and go look at them twice a year. That is the whole job.

You never know, but you can always be ready.

Sources

• FDA, Food Packaging and Other Substances that Come in Contact with Food: Information for Consumers

• FDA, Bisphenol A (BPA): Use in Food Contact Application

• CDC, How to Create and Store an Emergency Water Supply

• US EPA, National Primary Drinking Water Regulations

• US EPA, Use of Lead Free Pipes, Fittings, Fixtures, Solder, and Flux for Drinking Water

• NSF, NSF/ANSI 61: Drinking Water System Components, Health Effects

• Utah State University Extension, Water Storage and Emergency Use

• Oregon State University Extension, Water Storage for Emergencies

• University of Arizona Cooperative Extension, Water Storage Tank Disinfection, Testing, and Maintenance (AZ1586)

• Texas Water Development Board, The Texas Manual on Rainwater Harvesting

• Journal of Environmental Health Science and Engineering, Effects of storage time and temperature on antimony release from PET into bottled drinking water