Check whether your stored drinking water is set up safely, what to fix, and the date to empty and refill it — based on CDC emergency water storage guidance.
Describe how your water is stored to get a replace-by date and anything to fix
Storage conditions
Container Type
Water Source
Treatment Applied
Storage Temperature
Light Exposure
Container Seal
Date You Filled It
⚠ Please choose an option in every field and enter a valid fill date.
WaterTankCalculator.com — Water Storage Check
Your Results
Replace By
—
Empty, clean and refill on this date
Maximum Storage
—
Treat Before Storing?
—
Days Left
—
Container & Lid
—
Storage Spot
—
Next Step
—
Storage Timeline
📖 How To Use
How to Use This Calculator
Describe the containerChoose what the water is stored in and how it's closed. Drinking water should go in a clean, food-grade container with a tight lid.
Choose the source and treatmentTap water from a public supply is already treated. Well water, rainwater and river water need to be disinfected before they're stored for drinking.
Set where it's keptChoose the temperature and light where the water is stored.
Enter the date you filled itThe checker gives you the date to empty and refill it, how many days are left, and a list of anything to fix.
Important: If stored water looks cloudy, smells odd or has anything growing in it, don't drink it — whatever the date says. Empty the container, sanitise it and refill.
📐 How It Works
How Long Can You Store Water? The Rules This Checker Uses
There's no formula that can predict exactly when stored water becomes unsafe — it depends on how clean the water and container were at the start. So instead of guessing a number of days, this checker applies the CDC's emergency water storage guidance and checks your setup against it.
Type of stored water
How long to keep it
Source
Store-bought bottled water, unopened
Until the expiration date on the bottle
CDC
Tap water from a public supply, in a clean food-grade container
Replace every 6 months
CDC
Well, rain or other untreated water
Disinfect before storing, then replace every 6 months
CDC, US EPA
Open or loosely covered container
Don't rely on it for drinking
—
Tap water from a public supply doesn't need extra bleach before you store it, unless there's a boil-water notice. Water from a private well, rain or a stream does — use the bleach to water ratio calculator for the EPA dose.
How to prepare a storage container
Choose a food-grade containerNever reuse containers that held chemicals such as bleach, pesticides or fuel.
Wash and rinseWash with soap and rinse thoroughly with clean water.
SanitiseCDC suggests mixing 1 teaspoon of unscented household bleach in 1 quart (about 1 litre) of water, closing the container, and shaking so the solution touches every inside surface. Pour it out and let the container air-dry, or rinse with safe water.
Fill, seal and labelFill with safe water, close tightly, and label it "drinking water" with the date. Store it somewhere cool and out of direct sunlight, away from fuels and chemicals.
🎯 When To Use This
When This Checker Helps
🆘
Emergency Preparedness
CDC recommends at least 1 gallon per person per day for 3 days, and a 2-week supply if possible. Use this to know when to rotate it.
🏕️
Off-Grid & Remote Living
When stored water is all you have, check every container is set up to keep it safe — and date them all.
🌧️
Rainwater Harvesting
Rainwater isn't safe to drink straight from the roof. Treat it before storing it for drinking.
🏠
Rooftop Tank Users
A rooftop tank is a working tank, not long-term storage. Keep the lid sealed and clean and disinfect the tank regularly.
❓ FAQ
Frequently Asked Questions
How long can you store tap water?
CDC advises replacing water you store yourself every 6 months. Use a clean, food-grade container with a tight lid, label it with the date, and keep it somewhere cool and out of direct sunlight. Tap water from a public supply doesn't need extra bleach before storing unless there's a boil-water notice.
How long does bottled water last?
Use unopened store-bought water by the expiration date printed on it, as CDC advises. Keep it sealed, cool and out of sunlight until you need it. Unopened commercially bottled water is the most reliable emergency supply.
Can I store boiled water?
Yes, but boiling leaves no disinfectant in the water, so it's only as safe as the container you put it in. Let it cool, pour it into a sanitised container without touching the inside, and seal it. For long-term storage, adding bleach at the EPA dose gives protection that boiling alone doesn't.
How much bleach should I add to water I'm storing?
If the water isn't from a treated public supply, disinfect it using the US EPA emergency dose: 8 drops of 6% bleach or 6 drops of 8.25% bleach per gallon of clear water, then wait 30 minutes. That works out to roughly 110 ml of 6% bleach per 1,000 litres. Double the dose for cloudy water. Use our bleach to water ratio calculator for any volume.
Why keep stored water out of sunlight?
Sunlight warms the water, breaks down chlorine faster, and lets algae grow in see-through containers. Store water in a cool, dark place — a fairly constant 10–21°C (50–70°F) is ideal — and keep it away from fuels, paint and chemicals.
How long is rainwater safe to store?
Rainwater collected from a roof isn't safe to drink without treatment — it picks up dirt, bird droppings and debris. Filter or settle it, disinfect it, then store it in a sealed, food-grade container and replace it every 6 months like any other stored water.
What container is best for storing drinking water?
A food-grade water storage container with a tight lid — food-grade HDPE water jugs and drums are the most common. Never use containers that held chemicals such as bleach or pesticides. Milk jugs are a poor choice because they're hard to seal and break down; glass works but can break.
Does the 6-month rule apply to my rooftop tank?
No. The 6-month rule is for sealed containers you fill and put away. A rooftop tank is refilled and used every day, so the water doesn't sit for months. What matters there is a tight-fitting lid, a clean tank and a clean supply — clean and disinfect the tank regularly, and more often if you see sediment, algae or smell anything unusual.
How do I know if stored water has gone bad?
Cloudy or coloured water, odd smells, a slimy feel or visible growth all mean it shouldn't be drunk. But many germs cause no visible change at all, so don't rely on appearance alone — keep to the 6-month replacement rule, and replace any container that has been opened and left uncovered.
✅ Sources & Review
Sources and review
The storage rules on this page come from these references:
Reviewed by John Mac, PE, Water Systems Specialist
Texas-licensed Professional Engineer with 13+ years in residential water storage and 180+ tank projects. John writes and reviews every calculator on this site.
