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# HONG KONG URBAN COUNCIL
## ADDRESS BY CHAIRMAN
CHAIRMAN (in English):-Ladies and Gentlemen, may I call the meeting to order.
## MINUTES
The minutes of meeting held on 9 February 1993 were confirmed.
## PAPER
The following paper was laid on the table:
(1) Report to the Urban Council by the Secretary, Urban Council, for the month of February 1993.
## QUESTIONS
1. DR. IP KWOK-CHUNG asked the following question (in Cantonese):- I frequently receive complaints of water leakage at ceilings from occupants of private buildings. Upon receipt of such a complaint, I would normally refer it to the Department for follow-up action at once. Staff of the Department then visit the premises concerned but often fail to identify the real cause of the problem. The case is subsequently transferred to the Water Supplies Department which adopts the primitive method of meter-checking. Failing to find out the cause of the leakage, the WSD will give the complainant a reply that the problem has nothing to do with water supply and the case will be passed back to the USD. The procedures described above take nearly six months to complete but in the end many complaints remain unresolved. Understandably the complainants are disgruntled. Can we be advised of the following?
(a) In investigating complaints of water leakage at the ceiling, is the method adopted by the Department, namely depositing fluorescent green in waste water pipes, effective in finding out the source of leakage?
(b) Has the Department ever considered introducing more advanced methods, such as using detective equipment to locate the sources of leakage; and shortening the processing time for each case so as to lessen the nuisance of water leakage for our residents?
MR. PAO PING-WING, CHAIRMAN OF THE PUBLIC HEALTH SELECT COMMITTEE, replied as follows (in Cantonese):-Mr. Chairman, the question concerning the problem of water leakage from ceilings is in two parts. The first part queries the time taken in the investigation and asks whether the present testing system using colour dye is effective in tracing the source of leakages.
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Water seepage tends to be a very complex problem. To answer this question, it is useful to explain the common causes of the problem and the procedures that are necessary to try to trace the source.
The possible causes of leakages would usually be one or more of the following:-
(a) leakage from drain pipes on the external walls of the building such as rain/waste pipes, flushing water pipes;
(b) leakage from embedded discharge pipes from bathtubs, basins, sinks;
(c) leakage from mains water pipes, including hot water pipes connected to water heaters;
(d) defective water-proofing on floors or walls; and
(e) cracks inside cement concrete slabs or walls, resulting from structural defects to the building.
If leakage can be detected through dripping water or wet staining but the source cannot be readily ascertained, colour dye testing by USD Health Inspectors using fluorescent green would be conducted, as appropriate, at likely drain outlets in the premises immediately above the affected parts.
If, following colour dye tests in the premises above, visible dye staining appears in the premises experiencing the leakage problem, this would be taken as prima facie evidence of the source of the nuisance. Action can be then taken under sections 12(1)(a) and 127 of the Public Health and Municipal Services Ordinance, Cap. 132. Where colour dye tests fail to produce concrete results on the cause of seepage by visual inspection, water samples are then collected for analysis of any sub-visual dye by the Government Laboratory.
If, after physical inspection and colour dye testing by USD staff, it has proved impossible to trace the source, the case would then be referred to the Director of Water Supplies for further investigation. This obviously increases the length of the processing time.
If the Director of Water Supplies, having investigated the mains water system, still cannot find the cause, the matter would then be referred to the Director of Buildings and Lands to check if the seepage was caused by structural defects, again with a consequential lengthening of processing time.
This is the sequence of essential steps for determining the source of leakage. Any omission of any such steps in the investigation sequence could well result in the source of the problem being missed.
To date, colour dye testing is still considered the most practical means for USD staff to try to trace the source of leakage. USD staff are trained in this technique and it remains a very effective method of tracing leakage.
The second part of the question asks about the possible introduction of more advanced equipment to detect the source of leakage and thus to shorten the processing time for tracing water leakage.
Page 119 of 126
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208
HONG KONG URBAN COUNCIL
ADDRESS BY CHAIRMAN
CHAIRMAN (in English):-Ladies and Gentlemen, may I call the meeting to order.
MINUTES
The minutes of meeting held on 9 February 1993 were confirmed.
PAPER
The following paper was laid on the table:
(1) Report to the Urban Council by the Secretary, Urban Council, for the
month of February 1993.
QUESTIONS
1. DR. IP KWOK-CHUNG asked the following question (in Cantonese):- I frequently receive complaints of water leakage at ceilings from occupants of private buildings. Upon receipt of such a complaint, I would normally refer it to the Department for follow-up action at once. Staff of the Department then visit the premises concerned but often fail to identify the real cause of the problem. The case is subsequently transferred to the Water Supplies Department which adopts the primitive method of meter-checking. Failing to find out the cause of the leakage, the WSD will give the complainant a reply that the problem has nothing to do with water supply and the case will be passed back to the USD. The procedures described above take nearly six months to complete but in the end many complaints remain unresolved. Understandably the complainants are disgruntled. Can we be advised of the following?
(a) In investigating complaints of water leakage at the ceiling, is the method adopted by the Department, namely depositing fluorescent green in waste water pipes, effective in finding out the source of leakage?
(b) Has the Department ever considered introducing more advanced methods, such as using detective equipment to locate the sources of leakage; and shortening the processing time for each case so as to lessen the nuisance of water leakage for our residents?
MR. PAO PING-WING, CHAIRMAN OF THE PUBLIC HEALTH SELECT COMMITTEE, replied as follows (in Cantonese):-Mr. Chairman, the question concerning the problem of water leakage from ceilings is in two parts. The first part queries the time taken in the investigation and asks whether the present testing system using colour dye is effective in tracing the source of leakages.
Page 119 of 126
HONG KONG URBAN COUNCIL
Page 119 of 126
209
Water seepage tends to be a very complex problem. To answer this question, it is useful to explain the common causes of the problem and the procedures that are necessary to try to trace the source.
The possible causes of leakages would usually be one or more of the following:-
(a) leakage from drain pipes on the external walls of the building such as
rain/waste pipes, flushing water pipes;
(b) leakage from embedded discharge pipes from bathtubs, basins, sinks; (c) leakage from mains water pipes, including hot water pipes connected to
water heaters;
(d) defective water-proofing on floors or walls; and
(e) cracks inside cement concrete slabs or walls, resulting from structural
defects to the building.
If leakage can be detected through dripping water or wet staining but the source cannot be readily ascertained, colour dye testing by USD Health Inspectors using fluorescent green would be conducted, as appropriate, at likely drain outlets in the premises immediately above the affected parts.
If, following colour dye tests in the premises above, visible dye staining appears in the premises experiencing the leakage problem, this would be taken as prima facie evidence of the source of the nuisance. Action can be then taken under sections 12(1)(a) and 127 of the Public Health and Municipal Services Ordinance, Cap. 132. Where colour dye tests fail to produce concrete results on the cause of seepage by visual inspection, water samples are then collected for analysis of any sub-visual dye by the Government Laboratory.
If, after physical inspection and colour dye testing by USD staff, it has proved impossible to trace the source, the case would then be referred to the Director of Water Supplies for further investigation. This obviously increases the length of the processing time.
If the Director of Water Supplies, having investigated the mains water system, still cannot find the cause, the matter would then be referred to the Director of Buildings and Lands to check if the seepage was caused by structural defects, again with a consequential lengthening of processing time.
This is the sequence of essential steps for determining the source of leakage. Any omission of any such steps in the investigation sequence could well result in the source of the problem being missed.
To date, colour dye testing is still considered the most practial means for USD staff to try to trace the source of leakage. USD staff are trained in this technique and it remains a very effective method of tracing leakage.
The second part of the question asks about the possible introduction of more advanced equipment to detect the source of leakage and thus to shorten the processing time for tracing water leakage.
Page 119 of 126
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