Water tanks in apartments and condominiums are critical facilities that directly affect the quality of residents' daily water supply. Water tank cleaning is required by law, and neglecting it may result in penalties. This article provides a comprehensive explanation of the information managers need to know, from the types of water tanks and cleaning procedures to typical costs and how to choose a trustworthy contractor.
What types of water supply systems are used in multifamily housing?
Water supply systems for multifamily housing are broadly divided into two types: direct connection systems and receiving tank systems. Let us review the characteristics of each.
Direct connection system
This system supplies water directly to each unit without using a water tank. There are two types.
- Booster direct connection system: A method that uses a booster pump to deliver water to each floor. It can secure stable water pressure even in high-rise condominiums and can be installed in a space-efficient manner.
- Direct pressure connection system: A method that supplies water using only the pressure of the water mains. It is energy-efficient because no pump is required, but if water volume fluctuates significantly, it may negatively affect the surrounding area.
Receiving tank system
This system stores water supplied from the water mains in a tank before supplying it to each unit.
- Elevated tank system: A method that supplies water to each unit by natural downward flow from an elevated tank on the rooftop.
- Pump pressure system: A method that uses a pump to supply water from a ground-level storage tank to each unit. It has become widespread since the 1980s.
A receiving tank system has the advantage of securing one to two days of water as an emergency reserve in the event of a disaster. On the other hand, it requires regular inspection and cleaning maintenance, and a disadvantage is that the water supply must be shut off during cleaning.
Why is water tank cleaning required by law?
Even though a water tank is an enclosed space, it is still exposed to air, so mold, bacteria, insect remains, and similar contaminants may develop, making it difficult to maintain hygienic conditions over a long period. For that reason, cleaning and management are required by law.
Cleaning standards established by law
- Simplified private water supply system: Under Article 34-2 of the Water Supply Act, it is mandatory to conduct cleaning and inspection once each within a one-year period.
- Small-scale water tank water supply system: In accordance with the management standards of each municipality, cleaning and inspection at least once a year are required.
What happens if cleaning is neglected?
If water tank cleaning is neglected, it can lead to serious problems such as water quality deterioration, complaints, and penalties.
- Bad odor or discoloration of the water: Inadequate cleaning may result in the supply of unsafe water, creating a risk of health damage.
- Complaints from tenants: Changes in water quality can even become a reason for move-outs.
- Higher costs: If dirt becomes firmly stuck, cleaning costs may become more expensive than usual, and in the worst case the tank itself may need to be replaced.
- Penalties and fines: Management is required under the Building Sanitation Act, the Water Supply Act, and municipal ordinances, and violations may result in penalties.
What is the procedure for water tank cleaning?
Water tank cleaning follows the sequence of preliminary inspection, cleaning, disinfection, water quality testing, and preparation of a report.
When should cleaning be carried out?
The law requires cleaning "once within one year." Because the rule is not "once a year" but "once within one year," carrying it out more than once is considered preferable. Cleaning is also necessary when repairs, replacement, or new installation are performed, or when water has remained stagnant for a long period.
Work structure
Water tank cleaning is carried out by a work team of three or more people under the supervision of a certified water tank cleaning supervisor. Dedicated equipment must be used, and items such as water pumps, high-pressure washers, and residual chlorine meters are specified by law.
Preliminary inspection
This includes confirming the structure using facility drawings, checking conditions around the water tank, verifying that the manhole is locked, and confirming the operation of various equipment. Safety measures such as oxygen concentration measurement and electric shock prevention are also carried out.
Cleaning work
The water inlet valve is closed, and after drainage, water scale and bacteria are removed using sponges and scrubbing brushes. Any residual water generated during washing must be fully removed, and the condition before and after cleaning should be recorded in photographs.
Disinfection work
Disinfection is carried out using sodium hypochlorite or a similar agent, left in place for at least 30 minutes, and then finishing disinfection is performed. After leaving it again for at least 30 minutes, the tank is rinsed and refilled with water.
Water quality testing
Water quality testing after cleaning is mandatory. The following standards must be met.
- Turbidity: 2 degrees or less
- Color: 5 degrees or less
- Residual chlorine: 0.2 mg/L or higher
- Odor and taste: No abnormalities
Preparation and submission of the report
A report stating the building name and address, work date and time, names of workers, water quality test results, and photographs before and after the work is prepared and submitted.
What inspections are necessary besides cleaning?
In addition to cleaning, three elements are indispensable: routine inspections, water quality checks, and periodic inspections.
Routine inspections
Check on a regular basis for cracks, leaks, and damage to the main unit, the condition of insect screens, whether the manhole lid is locked, and the presence of foreign matter or dirt inside the tank. By building a stress-free property management system, these daily inspections can also be made more efficient.
Water quality checks
Check the color, odor, taste, and turbidity of the water using a clear glass cup. If water remains stagnant in the tank for more than one day, chlorine becomes diluted, so water usage should also be checked.
Response when abnormalities are found
If an abnormality is found, immediately stop the water supply, notify users, and then contact the health and welfare center or the water bureau.
Water tanks of 10 cubic meters or more
For water tanks with a capacity of 10 cubic meters or more, an annual inspection by a registered inspection agency is required by law.
What problems commonly occur with water tank cleaning?
The three most common problems are inadequate notice of water outages, reputational risk, and unscrupulous contractors.
Notice of the water outage was insufficient
It is effective to notify residents through both posting and notices, in stages such as one month in advance and one week in advance. Notices alone are easy to miss, while posting alone may be overlooked among other flyers.
Move-out risk caused by reputational damage
If foreign matter contamination is discovered during cleaning, it may lead to a loss of tenant trust and a higher move-out rate. Prevent this through thorough inspection, management, and cleaning.
You hired an unscrupulous cleaning contractor
It is important to be present on the day of cleaning and confirm the details of the work. Visually check whether dirt has been removed from the tank itself, whether it has been damaged, and whether there are any leaks after refilling.
What is the typical cost of water tank cleaning?
The cost of water tank cleaning varies depending on capacity. Typical price ranges are as follows.
- Up to 5 tons: from JPY 35,000
- Up to 10 tons: from JPY 50,000
- Up to 15 tons: from JPY 70,000
- Up to 20 tons: from JPY 80,000
- Up to 30 tons: from JPY 100,000
- Up to 50 tons: from JPY 120,000
To keep costs under control, it is advisable to obtain and compare estimates from multiple contractors. Contractors listed on municipal websites can also be a reliable option.
What are the key points in choosing a trustworthy water tank cleaning contractor?
Whether the contractor is properly registered, has extensive experience, and shows consideration for tenants are important criteria when choosing a contractor.
Choose a registered contractor
Water tank cleaning must be carried out by qualified personnel working for a contractor registered with the Minister of Health, Labour and Welfare. Taking into account rental management regulations as well, choose a contractor registered with the prefectural governor.
Do they have extensive experience?
The number of projects completed each year is an important indicator of a contractor's reliability. If this information is not published on the website, contact the contractor directly and confirm it.
Do they have sufficient tools and equipment?
Because water tanks vary in shape, installation location, and degree of contamination, contractors with a wider range of tools and equipment can respond more flexibly.
Do they show consideration for tenants and neighbors?
Choose a contractor that shows consideration for tenants and neighbors from the preparation stage before cleaning begins. It is important to confirm in advance matters such as the timing of notices, whether protective covering will be used, and whether cautionary notices will be provided.
Do they offer after-sales service and warranties?
Confirm whether the contractor will respond to problems after cleaning and whether there is an emergency contact in place. A contractor that offers 24-hour support can provide additional peace of mind in case anything happens.
Do they perform the work in-house?
If work is passed down to subcontractors or sub-subcontractors, there is a risk of inconsistent quality, so a contractor that clearly states it performs the work in-house is recommended.
Can they also handle cleaning other than the water tank?
If a contractor can also inspect and clean the area around the water tank and inspect the pressurized water supply equipment, it can help identify problems at an early stage.
Frequently Asked Questions (FAQ)
Q. How often should water tank cleaning be carried out?
The law requires it to be done "once within one year." If repairs are made or abnormalities occur, cleaning is required each time. In areas such as Tokyo and Osaka Prefecture, implementation at least once a year is mandatory.
Q. What happens if water tank cleaning is neglected?
In addition to the risk of health damage caused by deteriorating water quality, penalties or fines may be imposed for violations of the Building Sanitation Act and the Water Supply Act.
Q. How much does water tank cleaning cost?
The cost varies depending on capacity, but a general guide is from JPY 35,000 for up to 5 tons and from JPY 50,000 for up to 10 tons. Obtain and compare estimates from multiple contractors.
Q. How long will the water be shut off during cleaning?
It depends on the size of the water tank and the degree of contamination, but generally it is several hours. It is desirable to notify tenants in stages beginning one month in advance.
Q. Is water tank cleaning unnecessary for a direct connection system?
Yes, because a direct connection system does not use a water tank, there is no cleaning obligation. However, switching from a receiving tank system to a direct connection system requires municipal approval and construction work.
