Overview of Current In-Building Water Supply System Managementin Japan - Introduction of a Manual for Safety Management of these Systems Tetsuo Hayakawa*
Professor, Department of Environmental Health, Azabu University, Japan
1. Introduction
In 2005, WHO published Water Safety Plans (WSP) with the subtitle – Managing
drinking water quality, from catchment to consumer.1 According to the WSP and otherdocuments, to assure drinking water safety, several issues should be considered.
These include:1)

Source water pollution prevention;

2)

Treatment prior to distribution;

3)

Protection during distribution;

4)

Safe storage and distribution within buildings.

Of these, 1), 2), 3) can be regarded to function as barriers, where activities aredesigned to minimize the likelihood of contaminants entering the water supply or reduceor eliminate contaminants already present in the supply.
With the multiple barriers approach, each barrier provides an incremental reduction in
the risk of water becoming unsafe.
If there is a failure at one point, the other barriers continue to provide protection.
In Japan 1) to 3) are controlled by the water supplier (public sectors ) in common withother countries , and therefore the regulator can specify compliance requirements to thewater supplier. As a result, it is not so difficult to keep safe management in theserespects. However 4) may be outside the responsibility of the water supplier, and may
thus be implemented by building managers. In addition as this is the final step, failure isnot permitted.
So in-building water supply should be considered as a critical step to supply safe
drinking water to the consumer.
In-building water supply systems with water tanks have been controlled by the Water
Works Law in Japan since 1977. Since then owners of systems and/or building* 1-17-71, Fuchinobe, Sagamihara-City, Kanagawa-Pref., Japane-mail; hayak@azabu-u.ac.jp
1Water Safety Plans, WHO/SDE/WSH/05.06 ,2005- 93 -managers have tried to manage them more safely. To keep these systems - over one
million – safe, it is required that the owner should manage them safely. However, asowners normally do not have enough knowledge on the maintenance of such systems,
a maintenance manual on in-building water supply systems for owners with a littleknowledge on this issue is desirable.
2. Overview
2-1 Current status of In-Building Water Supply Systems with Water Storage Tanksin Japan
2-1-1

Tank volume Over 10 m3
Regulated by Water Works Law article 34-2;
The owner of the system is responsible for safety management of the system;
Technical maintenance protocol required including;Regular Inspection (at least once a year);
Regular Tank cleaning (at least once a year);
Pollution control procedure should be introduced if necessary.
Table -1 Status of Inspection of Water storage tanks (Data; MLHW)(Water Storage Tanks over 10m3)

Number of

1999

2000

2001

2002

2003

2004

184,401

190,150

194,278

196,381

201,809

206,451

157,781

162,186

165,034

165,408

167,497

166,839

85.6

85.3

84.9

84.2

83.0

80.8

tanks
Number ofinspected
tanks
Ratio (%)

Table-2 Status of non-compliance
Number of

1999

2000

2001

2002

2003

2004

65,31868,38670,816

68,59862,431

47,625

41.9

42.2

42.9

41.5

37.3

36.2

non-complying
tanks
Ratio (%)

- 94 -

2-1-2 Tank volume less than 10m3
Not regulated by Water Works Law;
Some Local Governments control them by local regulations.
Table-3 Current Situation of small scale In-Building Water Supply System Management(Tank Volume; Less than 10m3)
Number of

2000

2001

2002

2003

2004

745,414754,319

768,426

890,470907,055

24,381

24,65725,15631,15926,411

12,91812,06011,047

14,041

9,498

53.0

48.9

43.9

45.0

36.0

tanks
Number ofinspected
tanks
Number of
non-complying
tanks
Ratio (%)

As shown in these tables , the ratio of non-compliance remains at a high level despite
the existing regulations. In my study, some 10,000 systems that were found to havenon-complying tanks as a result of the previous year’s inspection are surveyed. Ofthese systems, some 50% have not been improved in regard to the previous year’s
non-compliance.
2-2 Examples of non-compliance
Examples of non-complying tanks are as followings:
1 Sewage flow into water tank from sewage tank;
2 Animal Carcasses are found in water tanks;
3 Because of decay of water tanks’ manholes, rainwater or sewage may flow into watertanks
This is caused by poor design of plumbing system, incorrect installation, alterations
and inadequate maintenance.
Fortunately the ratio of such severe violations is very low at 0.2%; however we should
try to improve this situation. There are two main measures for improvement. One is tochange a tank system to direct connection. Whilst this may be effective, in some cases it
may require a whole system alteration for high pressure supply. Another is to improve- 95 -

the maintenance level of tank supply systems. In this case it is important to improve thebuilding owners and/or managers’ knowledge.
This study focused on preparing an in-building water supply system maintenancemanual for building managers.
3. Introduction of the Maintenance Manual
The manual consists of the following articles;
1 Maintenance protocol
A building owner/manager is advised to prepare the maintenance protocol including:1) Maintenance target;
2) Regular inspection of a whole system and each component;
3) Regular cleaning;4) Emergency stop water supply;5) Keeping documents on maintenance;6) Cost for maintenance.
2 Selection of Water Tank Cleaning and Inspection Firm
1) Free available information of water tank cleaning and inspection firms;
2) Cleaning and inspection in the presence of building manager;
3) Hearing of the results of cleaning/inspection;4) Receiving an improvement plan;5) Combination of building manager, relevant firms, water supplier and government.
Other issues which should be considered together with the implementation of themaintenance manual are;1) To introduce a recognition system of buildings with good maintenance; this may raisethe value of the building.
2) To strengthen the relationship between building managers, cleaning/inspection firms,plumbers, water suppliers and government.
It is hoped that many owners/managers of in-buildings water supply systems andrelevant specialists can become familiar with this manual in the near future. As a result
maintenance levels of in-building water supply systems would be improved and then astep towards the goal of Safe Drinking Water Supply to All will be achieved.

- 96 -

Overview of Current In-Building
Water Supply System
Managementin Japan

1. Introduction• In 2005
WHO published Water Safety Plans (WSP) withsubtitle – Managing drinking water quality fromcatchment to consumer.[1] According to theWSP and other documents, to assure drinkingwater safety, several issues should beconsidered , for example,-Introduction of a Manual for Safety
Management of these Systems –Tetsuo Hayakawa
Professor, Environmental Health College,Azabu University , Japan[1]
Water Safety Plans,
WHO/SDE/WSH/05.06 ,2005

Water Safety Plan

Ｉssues should be considered

Risk Management and Assessment
From Catchment to Consumer

According to the WSP and other documents,
Ｉｓｓｕｅｓ to assure drinking water safety :1) Source water pollution prevention;2) Treatment prior to distribution;
3) Protection during distribution;4) Safe storage and distribution withinbuildings.

Three Components
1) System assessment
2) Risk Management
3) Maintenance Protocol

WHO Guidelines for
Drinking –water Quality
3rd.Ed.
（Sept. 2000)

Ａ critical step to supply safe
drinking water

Ｔhe Ｍultiple Ｂarrierｓ Ａpproach
Issues 1), 2), 3) can be regarded tofunction as barriers, where activities aredesigned to minimize the likelihood ofcontaminants entering the water supply or
reduce or eliminate contaminants alreadypresent in the supply.
Ｅach barrier provides an incremental
reduction in the risk of water becoming
unsafe.

• In Japan 1) to 3) are controlled by the watersupplier (public sectors )• Ｉt is not so difficult to keep safe management.
• 4) may be outside the responsibility of the watersupplier, and may thus be implemented bybuilding managers• Ｔhis is final step, failure is not permitted.

Current status of In-Building
Water Supply Systems with
Water Storage Tanks in Japan

Table -1 Status of Inspection of Water storage tanks ( Data;MLHW)( Water Storage Tanks over 10m3 )• So In-building Water Supply should
be considered as a critical step to supply safe
drinking water to the consumer.

Tank volume Over 10 m3１） Regulated by Water Works Law article 34-2
・An owner of the system is responsible for safety
management of the system .
２） Technical maintenance protocol required including;
・Regular Inspection (at least once a year);・Regular Tank cleaning (at least once a year);・Pollution control procedure should be introduced if
necessary

1999

2001
2002
2003
2004
Number of tanks
184,401 190,150 194,278 196,381 201,809 206,451
Number of inspected tanks
157,781 162,186 165,034 165,408 167,497 166,839
Ratio (%)
85.6
85.3
84.9
84.2
83.0
80.8

- 97 -2000

Table-2 Status of non-compliance
1999

2000

2001

2002

2003

Tank volume less than 10m3

2004

Number of non-complying tanks
65,318 68,386 70,816 68,598 62,431 47,625

41.9

42.2

Ratio (%)
42.9
41.5

37.3

• Not regulated by Water Works Law ;Some Local Governments control them by
local regulations.

36.2

Table-3 Current Situation of small scale In-Building Water SupplySystem Management( Tank Volume; Less than 10m3)

2000
745,414
24,381
12,918
53.0

2001

2002
2003
Number of tanks
754,319
768,426
890,470
Number of inspected tanks
24,65725,15631,159Number of non-complying tanks
12,06011,047
14,041
Ratio(%)
48.9
43.9
45.0

Examples of non-compliance• Examples of non-compliance are asfollowings :1 Sewage flow into water tank from sewagetank
2 Animal Carcasses are found in watertanks;
3 Because of decay of water tanks’manholes, rainwater or sewage may flow
into water tanks

2004
907,055
26,411
9,498
36.0

ＥＸ．２ Ａｌｇａｅ in a Tank

ＥＸ．１ Ｃｒｏｓｓ ｃｏｎｎｅｃｔｉｏｎ

EX.3 Decay of a ROOF

Two main measures forimprovement
1) To change a tank system to direct connection,
this may be effective in some cases it may require
whole system alteration for high pressure supply
2) To improve maintenance level of tank supplysystems
it is important to improve building owners and/ormanagers’ knowledge.

- 98 -Water Tanks in Shingapore

Water Tanks on Roofs in Okinawa

2 Selection of Water Tank
Cleaning and Inspection Firm

Introduction of theMaintenance Manual

1) Free available information of water tankcleaning and inspection firms;
2) Cleaning and inspection in the presence ofbuilding manager;
3) Hearing of the results of cleaning/inspection;4) Receiving an improvement plan;5) Combination of building manager , relevant
firms ,water supplier and government.

1 Maintenance protocol
A building owner/manager is advised to prepare
the maintenance protocol including
1) Maintenance target
2) Regular inspection of a whole system and eachcomponents
3) Regular cleaning
4) Emergency stop water supply5) Keeping documents on maintenance6) Cost for maintenance

Other issues together with implementation ofmaintenance manual（参考）横浜市給水管理適合施設表示制度

1) To introduce recognition system ofbuildings with good maintenance, this may
raise the value of the building2) To strengthen relationship between
building managers, cleaning/inspection
firms, plumbers, water suppliers andgovernment○目的： 設置者の管理意識を高め，安全で衛生的な受水槽水を確保する
平成６年６月から実施
当初（市が認定）⇒平成１６年度に表示制度に改正⇒検査機関（協定）に移行○管理の良好な施設が自ら表示できる。
○給水管理適合施設表示マーク（プレート）・有効期限シールの交付○施設利用者に見える場所に掲示- 99 -

７年 月

有効期限表示プレート