How Much Emergency Water Do You Need in Japan? A Simple Guide for Earthquakes and Typhoons

Living in Japan has made emergency water one of those things I prefer to keep at home all year.

Earthquakes can happen without warning. Typhoons are different because we usually have some time to prepare, but strong storms can still bring power outages or disruptions to essential services.

At our house, we normally keep two cases of bottled water. Each case contains six 2-liter bottles, so we have about 24 liters on hand. If a large typhoon is approaching, we often buy another two cases.

But is that actually enough?

In Japan, a useful emergency guideline is about 3 liters of drinking and cooking water per person per day. A good starting point is at least three days, while having enough for about a week provides a larger buffer.

So before buying random cases of water, it helps to calculate how much your household actually needs.

How Much Emergency Water Should You Store per Person?

Using 3 liters per person per day, here's a simple way to estimate your emergency water supply.

Household	3 Days	7 Days	2L Bottles for 3 Days
1 person	9 L	21 L	5 bottles
2 people	18 L	42 L	9 bottles
3 people	27 L	63 L	14 bottles
4 people	36 L	84 L	18 bottles

For example, a two-person household needs about 18 liters for three days. That's nine 2-liter bottles.

If storing a full week's supply seems difficult, especially in a small Japanese apartment, starting with three days is much more realistic. You can gradually add more if you have the space.

And if you have pets, don't forget them when calculating your emergency supply. They need their own drinking water too.

Does 3 Liters Mean You Need to Drink 3 Liters a Day?

No. The 3-liter guideline isn't just about what you drink.

It includes drinking water and water needed to prepare food.

During an emergency, you may need water for instant noodles, freeze-dried meals, rice, medicine, or other simple meals.

Water for washing, cleaning and other household needs should be considered separately.

I find it easiest to think about emergency water in two categories:

Bottled water: drinking and cooking

Utility water: washing and other household needs

This distinction becomes especially useful when preparing for a typhoon, because there are some things you can do shortly before the storm arrives that aren't possible with an earthquake.

How We Store Emergency Water at Home in Japan

We normally keep two six-bottle cases of 2-liter water at home, giving us 24 liters in total.

If a strong typhoon is forecast, we may buy another two cases. That brings our supply to around 48 liters.

That doesn't mean 48 liters is the right amount for everyone. It depends on your household size and how many days you want to prepare for.

What changed the way I look at our water supply was counting liters instead of cases.

Two cases sitting in the house can look like quite a lot. But once you compare 24 liters with the amount your household needs per day, it's much easier to see how long it would actually last.

Bottled water is easy to buy at supermarkets, drugstores and convenience stores in Japan, but I don't want to depend on going out to buy it right before an emergency.

Keeping a basic supply at home is much simpler.

For Earthquakes, Keep Water Ready All Year

One big difference between earthquake and typhoon preparedness is timing.

You can't wait for an earthquake forecast before buying water.

That's why we keep our basic supply at home throughout the year rather than treating bottled water as something we buy only when there is an emergency warning.

We don't leave those bottles untouched forever, either.

We check the dates, drink the older bottles during everyday life, and replace what we use with newer ones.

That way, our emergency supply is constantly being refreshed without requiring a separate stockpile that we have to remember to replace all at once.

This has been much easier for us than buying emergency water, putting it away somewhere and forgetting about it for years.

If you prefer to keep a separate emergency supply, long-life bottled water designed for disaster storage is another option in Japan.

Before a Typhoon, You Have More Time to Prepare

Typhoons are different because their approach can usually be followed through weather forecasts.

When a major typhoon is expected, I check our bottled water and may add another two cases before the weather gets bad.

If there is concern about a possible water outage, another option is to fill the bathtub with tap water for household use before the typhoon arrives.

The important point is that bathtub water and bottled drinking water serve different purposes.

The water stored in the bathtub should not be treated as drinking water. Think of it as additional utility water that may be useful if your normal water supply is interrupted.

One thing to keep in mind, especially after an earthquake, is that damaged sewer or drainage systems may make it unsafe to use toilets and drains normally.

Don't assume that stored bathtub water can automatically be poured into a toilet after a disaster. Check instructions from your local municipality or building management if there has been damage to local water or sewer infrastructure.

Don't Store Bottled Water and Forget About It

Buying several cases of water is only the first step.

Bottled water has dates printed on the packaging, so it's worth checking your supply occasionally rather than leaving it untouched indefinitely.

Our routine is very simple:

Use the older bottles first, then replace them with new ones.

We already drink bottled water at home, so this doesn't feel like special disaster preparation. It has simply become part of our normal shopping routine.

This approach also means we are less likely to discover that several cases have been sitting forgotten in storage for years.

When storing bottled water, follow the storage instructions on the product and avoid places exposed to direct sunlight or excessive heat.

A week's supply can also take up more room than you might expect. If keeping everything in one place is difficult, dividing your supply between suitable storage areas may be more practical.

Start With Three Days and Build From There

Preparing for disasters in Japan can feel overwhelming.

There are emergency foods, flashlights, batteries, power banks, portable toilets and many other things you might want to keep at home.

You don't have to organize everything at once.

For water, start with one simple calculation:

Number of people × 3 liters × 3 days

Then compare that number with what you already have at home.

If you have pets, add drinking water for them as well.

Once you have a basic three-day supply, you can work toward storing enough for a longer period if your budget and storage space allow.

The way we prepare is simple. We keep two cases of 2-liter bottled water at home throughout the year, use the older bottles and replace them as we go. When a large typhoon is approaching, we may add another two cases and think about securing extra utility water as well.

Earthquakes and typhoons require slightly different preparation, but the basic lesson I've learned from living in Japan is the same: water is much easier to prepare before you need it.

You don't need a perfect disaster stockpile today. Start by checking how many liters of water are already in your home and how many days that would realistically last.

You Might Also Like

👉What People Buy Before a Typhoon in Japan: A Foreigner’s Guide to Home Center Shopping
👉How Long Does a Fridge Stay Cold Without Power? Food Safety During an Outage in Japan

👉What to Bring Inside Before a Typhoon in Japan: Balcony and Outdoor Safety Tips

References

Ministry of Agriculture, Forestry and Fisheries (MAFF), Japan — guidance on household emergency food and water supplies

Cabinet Office, Government of Japan — disaster preparedness guidance

Ministry of Land, Infrastructure, Transport and Tourism — disaster-related sewerage and sanitation guidance