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Drinking Water Standards and Enhanced Water Quality Monitoring Programme

Preamble

Over the years, the Water Supplies Department (“WSD”) has been supplying drinking water in full compliance with the World Health Organization’s Guidelines for Drinking-water Quality (“WHO Guidelines”). WSD has implemented a water quality monitoring programme by taking water samples annually from water treatment works, service reservoirs, connection points and some randomly selected publicly accessible taps (such as those in shopping centres, clinics, community facilities, sports grounds, markets, government offices and estate management offices) with primary focus to check quality of water as supplied to consumers for compliance with the WHO Guidelines. WSD will enhance its current water quality monitoring programme by further taking random water samples from all over the territory to monitor the quality of drinking water at the consumers’ taps. Details of the drinking water standards of Hong Kong and the Enhanced Water Quality Monitoring Programme (“Enhanced Programme”) are provided in the ensuing paragraphs.

Enhanced Water Quality Monitoring Programme

Enhanced Water Quality Monitoring Programme

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Enhanced Water Quality Monitoring Programme Poster

Enhanced Water Quality Monitoring Programme Poster

Hong Kong Drinking Water Standards and Enhanced Programme

Parameter Potential Sources Risk of Contamination
Antimony (“Sb”)
GV* = 20 µg/L
  • Antimony is a possible replacement for lead in solders.
  • Solder materials using antimony are not commonly available in the market. The risk of exceedance for oral exposure to antimony from drinking water is known to be low.
Cadmium (“Cd”)
GV*= 3 µg/L
  • Cadmium is a possible impurity in the zinc of galvanized iron (“GI”) pipes, silver brazing materials, fittings, water heaters, water coolers and taps.
  • The use of unlined GI pipes has been banned in Hong Kong since 1995 and the risk of excessive leaching of cadmium from unlined GI pipe is known to be low.
  • The lining in the lined GI pipes have guarded against possible leaching of zinc.
  • Silver brazing materials with excess levels of cadmium are not commonly available in the market.
  • The risk of exceedance for oral exposure to cadmium from drinking water is known to be low.
Chromium (“Cr”)
PGV* = 50 µg/L
  • Due to defects during the electroplating process, chromium may seep into the wetted surfaces of taps leading to possible dissolution of chromium into drinking water.
  • As taps hold very small amount of water (less than 150mL) under stagnant condition, the leached chromium from water taps, if any, could be flushed away within one to two seconds after turning on the taps.
  • The risk of exceedance for oral exposure to chromium from drinking water is known to be low.
Copper (“Cu”)
GV*=2000 µg/L
  • Copper may come from internal corrosion of copper pipe in water of pH below 6.5.
  • The risk of exceedance is low in Hong Kong as the pH of the drinking water is slightly alkaline (pH 8.2 to 8.8) to prevent copper corrosion from the pipe.
Lead (“Pb”)
PGV* = 10 µg/L
  • Lead may come from leaded solders and copper alloy fittings especially the newly copper alloy fittings.
  • Leaded solders are prohibited for use in inside services. WSD has enforced strict control on the use of leaded solders through (i) material control; (ii) prior written permission from the Water Authority if the method of soldering is to be used; (iii) material check; and (iv) water sampling test.
  • WSD has introduced a systematic flushing protocol for newly installed inside services to reduce the leaching of lead from the new internal plumbing system.
Nickel (“Ni”)
GV* = 70 µg/L
  • Due to defects during the electroplating process, nickel may seep into the wetted surfaces of taps leading to possible dissolution of nickel into drinking water.
  • As taps hold very small amount of water (less than 150mL) under stagnant condition, the leached nickel from water taps, if any, could be flushed away within one to two seconds after turning on the taps.

Table 1 - Possible Sources and Risk of Contamination of the Six Metals in Internal Plumbing System

*Guidelines for Drinking-water Quality published by World Health Organization in 2017:  GV=Guideline Value; PGV = Provisional Guideline Value

i) after confirming the test results, immediately notify the RC and occupier (and the owner as far as practicable) of the concerned premises, and in some cases the relevant Government bureaux and departments and the relevant licensing authorities, of the water test results by hand and by mail, and request them to notify other water consumers in the same premises of the exceedance;
ii) provide information on the related health risks. For details, please refer to the pamphlets “What you need to know about Lead in Drinking Water on health?” and “What you need to know about antimony, cadmium, chromium, copper and nickel in drinking water on health?” published by Department of Health;
iii) advise on possible mitigation measures, details are provided under paragraph 8 below;
iv) provide technical information such as possible source of the exceedance and options to deal with the problem including the engagement of designated person(s) (e.g. licensed plumbers) to rectify the internal plumbing system; and
v) offer the RC a one-off free investigation into the cause and location of exceedance. Alternatively, the RC can choose to engage a qualified person (i.e. building services engineer, building surveyor or licensed plumber who has been included in the list of qualified person for the investigation) for conducting the investigation work.
Moreover, WSD will take appropriate follow-up actions for certain types of premises.  For the premises where drinking water is supplied for potable consumption either by the general public (e.g. restaurants) or, in case of lead exceedance, the more easily affected groups (e.g. kindergartens), the below additional measures will be taken:
  vi) WSD will work with the RC and occupier of the premises with a view to implementing contingent measures for stopping contaminated water that exceeds the respective GVs/GPVs of certain parameters from being supplied, such as arranging alternative sources of water supply including installation of certified water filters tested by accredited organisation for potable consumption and engage a plan for subsequent rectification of the internal plumbing system.
WSD will undertake to follow up the progress of the mitigation/rectification work bearing in mind the overriding public health interest.  Whilst the respective RC and occupier will normally take cooperative action to carry out the necessary mitigation or long term rectification measures, in case there is no effective measures being carried out resulting in public health being jeopardised, WSD will consider taking further actions including appropriate enforcement action in order to protect public health.

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