1. Why Having Running Water in Japan Is Not as Normal as It Seems
In Japan, about 98% of people have access to running water as of 2021. In Tokyo and Osaka, it is 100%.[1] This means three things happen at once: water comes out whenever you turn the tap, day or night, and it is safe to drink.
Making this happen requires a complex system. Water must be created, stored, and sent without any breaks in the chain. It also must stay clean while traveling through pipes. This was not always true. In the late Meiji era (late 19th century), only 8.4% of people had running water.[2] Most used wells or fetched water from rivers. Today’s system took over 100 years to build.
2. How Tap Water Starts as Rain on Mountains and Forests
If you trace tap water backward, where does it end? The answer is rain that fell on mountains. Forests play a key role here. If rain ran straight into rivers, we would have floods when it rains and shortages when it does not.
Instead, some rain soaks into the forest soil. Leaves and dirt act like a sponge with many holes, absorbing water and releasing it slowly over time. This is why forests are sometimes called "green dams." However, this does not mean forests prevent all floods; their effect during heavy rain is limited.
Water from forests becomes rivers. The main sources for tap water are river water (the most common), dam water (stored in wet seasons and released in dry ones), and groundwater (from wells). All of these start as rain. Used water returns to rivers or the sea, evaporates, and becomes rain again. Our tap water is just borrowing from this cycle.
3. How Purification Plants Make River Water Safe to Drink
River water cannot be drunk directly. It contains visible dirt and invisible microbes. It is sent to a water purification plant, where it goes through four main steps.[3]
First, chemicals are added to clump tiny particles of dirt together so they become big enough to sink. Second, the water flows slowly, allowing these clumps to settle at the bottom. Third, the water passes through a layer of sand to catch any remaining small particles. Fourth, chlorine is added to kill bacteria. The chlorine keeps working even after treatment, ensuring the water stays safe as it travels.
4. How Clean Water Travels From the Plant to Homes
You might think pumps push water all the way to your house. In many places, that is not how it works. Water leaving the purification plant first goes into a large tank called a distribution reservoir. These tanks are usually built on hills or high ground.
From there, gravity pulls the water down to lower areas. This saves energy and money because fewer pumps are needed. It also helps if power fails; stored water can keep flowing for a while. Reservoirs also act as cushions. Water use changes throughout the day—high in the morning and evening, low at night. But purification plants cannot change their output quickly. The reservoir stores extra water when use is low and releases it when use is high.
5. How Water Gets Up to Taps in Tall Apartment Buildings
This is the biggest question: how does water come out of taps in tall buildings? The pressure in underground pipes is not very high. It can usually only push water up to about 3 or 4 floors.[4] This varies by location, so treat it as a rough guide.
For higher floors, there are three main methods. The first is "direct pressure," which uses the pipe pressure itself; this works for low to mid-rise buildings. The second is "direct booster," where pumps at the bottom of the building add extra pressure to push water up. This is common in new mid-to-high-rise buildings.[4] The third method involves storing water in a tank, pumping it to the roof, and letting gravity bring it down. This is used for very large buildings or those needing backup supply during outages.
6. How Japan's Modern Water System Began in Yokohama in 1887
Modern tap water in Japan began on October 17, 1887, in Yokohama.[7] An English engineer named Henry Spencer Palmer led the design. He had been surveying since 1883 and used new technologies like cast iron pipes, pumps, and filtration pools to create a system that sent water under pressure without stopping.[2]
Why did it start in port cities? After Yokohama, systems spread to Hakodate, Nagasaki, Osaka, Tokyo, Hiroshima, and Kobe—all ports.[2] One major reason was disease. Port cities were vulnerable to illnesses arriving by ship. Diseases spread by drinking dirty water were a huge threat. Preventing sickness was one of the big reasons water systems expanded. Chlorine disinfection became widespread in the 1920s.
The progress has been steady. By the end of the Meiji era, there were 23 water systems with an 8.4% adoption rate. By 1925, there were 106 systems with a 20.7% rate.[2] Today, it is about 98%.[1]
7. Why Tap Water Is Drinkable in Japan but Not in Some Other Countries
In some countries, people are told not to drink tap water. In Japan, many areas allow you to drink it directly. Why? For tap water to be drinkable, several conditions must be met: purification must be thorough, pipes must not leak dirt (old pipes or low pressure can cause issues), and disinfection must remain effective throughout the journey. It also requires money and people to maintain it constantly.
Taste differences come from minerals dissolved in the water. Water with many minerals is "hard," while water with few is "soft." Japan’s water is mostly soft, making it feel gentle in the mouth. Europe has more hard water areas. This depends on the soil layers the water passes through. Neither is better or worse; it is just different. Japan’s water tends to be softer because its islands are narrow and rivers are short and steep, so water does not stay underground long enough to absorb many minerals.
Even within one country, conditions vary between cities and rural areas. Sometimes, old pipes inside buildings make water unsafe even if the main supply is good. Some cultures prefer bottled water for taste or smell, even if tap water is safe.
8. The Problem of Aging Water Pipes in Japan
Many of Japan’s water pipes were laid rapidly during the high-growth period decades ago. This means many are entering a time when they become old at the same time. Old pipes can leak or break, but fixing them requires digging up roads, which is costly and slow.
Another challenge is population decline. Maintenance costs depend on the length of pipes, not how many people use them. As fewer people live in some areas, they must support the same amount of pipe infrastructure. This burden is heavier in regions with low populations.
Disasters also pose risks. Earthquakes can break pipes, stopping water flow. Repairing underground pipes after a major quake takes time because each section must be dug up and fixed individually. The fact that water flows when you turn the tap depends on someone constantly maintaining it. We only notice this effort when it stops.
9. How You Can Investigate Your Own Home's Water
You can check your own home and neighborhood. Look for the water meter near your entrance or under a ground cover outside. If the numbers move when all taps are closed, there might be a leak.
If you live in an apartment, look at the roof from a place where it is safe to see it. A square tank on top means the building uses the storage-and-drop method. If there is no tank, it likely uses booster pumps. On high hills in your town, look for large tanks or round buildings; these could be distribution reservoirs.
Ask to see a water bill. It shows how many cubic meters you used. One cubic meter equals 1,000 liters. How many bathtubs is that? This invisible infrastructure connects your home to the wider world. For more on hidden systems, read "Why Does the Internet Connect With the Whole World?"