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■What exactly are "water quality standard items"? The quality of tap water is strictly managed by "water quality standard items" established by ministerial ordinances based on the Water Supply Act. These have legal binding force, and water suppliers are obligated to provide water that meets these standards and to conduct inspections. ■Why are there also stages called "water quality management target setting items" and "items for consideration"? In fact, in addition to water quality standard items, there are categories such as "water quality management target setting items," which have a similar status, and "items for consideration," which are at the information gathering stage. Substances for which the reliability of toxicity assessment and the examination of detection realities are insufficient are initially placed in these two categories, and once scientific knowledge is solidified, they are upgraded to formal water quality standard items. ■Have standards been increasing recently? An example of this system in action is the organic fluorinated compounds PFOS and PFOA. For a long time, they were classified as water quality management target setting items, but following the solidification of toxicity assessments, they were upgraded to formal water quality standard items in April 2026. Standards are not fixed; they continue to be updated as new knowledge accumulates. If you are having trouble with water quality management in your facilities, please feel free to consult with us first.

■What is the "Water Supply Act" that underpins water quality standards? The quality of tap water is supported by the "Water Supply Act," a law enacted in 1957 (Showa 32). Water quality standards are the "requirements that tap water should meet," established by ministerial ordinances based on this Water Supply Act, and they mandate water suppliers, such as prefectures and municipalities, to provide water that meets the national quality standards. ■How often are the standards reviewed? Water quality standards are not set in stone; they are revised according to the latest findings through a "sequential revision method," with reviews of standard items and values occurring almost every year. ■Why are there currently 51 standard values? As of April 2021 (Reiwa 3), there are 51 different items with established standard values in the water quality standards. This is the result of over 60 years of sequential revisions since the enactment of the Water Supply Act. The large number of standards is a testament to the detailed history of ensuring the safety of tap water. If you are having trouble with water quality management in your facilities, please feel free to consult us.

■What exactly are "water quality standards"? Tap water contains various substances that are not visible to the eye, many of which can affect health, taste, and smell. Water quality standards refer to the quality regulations for tap water established by the government regarding these substances. Specific items and values are defined in the "Ministerial Ordinance on Water Quality Standards" based on Article 4 of the Water Supply Act. ■Who is obligated to comply with these standards? The obligation to comply with the standards falls on water suppliers such as prefectures and municipalities that provide tap water. It is legally mandated to deliver water that meets the standards, and the safety of the tap water we consume daily is supported by this system. ■Why are the standards not set in stone once established? Water quality standards are reviewed periodically through a system called "sequential revision." As analytical techniques and research on health impacts advance, substances that were previously overlooked may be added to the standards. By continuously updating in line with the latest findings, the safety of tap water is maintained. If you have concerns about water quality management in your facilities, please feel free to consult us first.

■What is the unit of electrical conductivity "S/m"? The electrical conductivity of water is a value that indicates how easily electricity can pass through it; the larger the value, the easier it is for electricity to flow. The unit is "S/m (siemens per meter)," and it can also be expressed in terms of size as "mS/m" or "μS/cm." ■What is the electrical conductivity of tap water? It varies by region, but in Japan, the electrical conductivity of tap water is generally considered to be around 10-20 mS/m. When measured with a conductivity meter, the value can sometimes be around 20 mS/m. ■Why does tap water not have an electrical conductivity of 0? Even after purification treatment, tap water retains minerals such as calcium and magnesium as ions, which are generally explained as the source of conductivity. Pure water, which contains almost no ions, does not conduct electricity well, leading to a significant difference from the values of tap water. If you have concerns about water quality management, please feel free to consult us first.

■What is the difference between well water and tap water? Tap water is treated with chemicals for sterilization, enhancing its safety, while well water is simply drawn from underground without undergoing disinfection processes. ■Is not all well water safe? Generally, well water used for drinking as "mineral water" is drawn from deep wells, which are considered to be about 30 meters or more below the surface. In contrast, water from shallow wells (within about 8 meters from the surface), commonly found in households, is not considered as safe compared to deep well water. ■Why is deep well water considered safe? Deep well water passes through multiple layers of soil before reaching the depths, providing thorough filtration. It is often sandwiched between clay layers, which can offer antibacterial effects, and it accumulates rich minerals during its journey through the soil layers. On the other hand, shallow wells are more susceptible to surface contamination due to their shallow depth, often rendering the water undrinkable. If you are having trouble managing the quality of your well water, please feel free to consult us.

■What is the difference between industrial water and tap water? Tap water is strictly managed for quality to be safe for human consumption, while industrial water is defined by the quality needed for use in factories. It is not filtered or sterilized, and only the clear liquid after removing sediments is used, making it unsuitable for drinking. However, it is supplied at a lower cost through a separate water supply network from tap water. ■Why was this separate water supply network created? In fact, this system was initiated due to the serious ground subsidence that occurred in various areas when factories excessively pumped groundwater. While the government regulated the extraction of groundwater, it established a dedicated water supply network to provide alternative sources such as river water to factories. This is why it is not subject to the Water Supply Act. ■Where is industrial water actually used? It is utilized in various situations within factories, such as for cleaning machines, cooling iron, and providing water for boilers. Beyond factories, it is also used in a wide range of scenarios, including washing trucks and in thermal power plants.

■What is the difference between pure water and tap water? Tap water contains minerals such as calcium and magnesium, chlorine for disinfection, and aluminum used in the purification process. On the other hand, pure water is water from which such impurities (ions and foreign substances) have been removed, and it is theoretically considered safe to drink as it does not contain harmful substances for the human body. ■How is the purity of pure water measured? The purity of water is generally measured by its "specific resistivity," which indicates how difficult it is for electricity to pass through. The fewer ions present in the water, the harder it is for electricity to pass through, so a higher specific resistivity indicates higher purity. Generally, water with a specific resistivity of 18.2 MΩ·cm or more is called "ultrapure water," while water with 0.2 MΩ·cm or more is referred to as "pure water." ■Is it really safe to drink pure water? Some experts point out that because pure water lacks impurities, it has a strong ability to dissolve surrounding substances, which could potentially leach minerals that the body retains. While this is not a medically established theory, it is good to be aware that such views exist.

■Why can tap water in Japan be drunk as is? In Japan's water purification plants, the processes of sedimentation and filtration are thoroughly conducted to remove turbidity and microorganisms, followed by chlorine disinfection. Some facilities combine advanced treatments to eliminate odor-causing substances, and strict process management supports safety. ■What is the mechanism that ensures safe water reaches the tap? In fact, regulations under the Water Supply Act require that a certain concentration of chlorine remains in the water that comes out of the tap. This residual chlorine prevents the growth of bacteria in the pipes after leaving the purification plant, and the presence of chlorine smell in tap water can be considered a sign of safety. ■Why can't tap water be drunk in many countries? The high costs associated with establishing water purification facilities and piping networks are considered a factor, as countries lacking sufficient funds and technology struggle to keep up with the necessary infrastructure. It is said that many people around the world still do not have access to safe drinking water.