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WSD Circular Letter No. 5/2023 
水務署通函第5/2023號

Water Sampling Protocol for Commissioning of Fresh Water Plumbing System

內部食水供水系統驗收的取樣規程

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Introduction 簡介

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At Enviro Labs, we provide comprehensive water sampling and testing services tailored to meet the latest requirements for commissioning freshwater plumbing systems. Adhering to the standards set forth by the Hong Kong Water Supplies Department (WSD) Circular Letter No. 5/2023, our services ensure compliance, safety, and peace of mind for plumbers, property developers, contractors, and facility managers.

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在 Enviro Labs，我們提供全面的水質採樣與測試服務，專為新鮮供水系統的調試需求量身打造。我們的服務完全符合香港水務署《水務署通函第 5/2023 號》中最新要求，協助水喉匠、發展商、承建商和設施管理人員確保合規、安全及安心。

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Overview of Testing Requirements 測試要求概覽

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As per WSD Circular Letter No. 5/2023, water sampling protocols for commissioning new freshwater plumbing systems have been updated to streamline procedures and maintain strict quality standards. The protocol applies to all new plumbing works and systems submitted with Form WWO 46 Part IV from September 18, 2023, onward. Key aspects include:

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根據《水務署通函第 5/2023 號》，新鮮供水系統調試的水質採樣程序已經更新，以簡化流程並保持嚴格的質量標準。該要求適用於 2023 年 9 月 18 日起提交 WWO 46 表格第四部分的所有新供水系統。以下是主要細節：

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  1. Sampling Procedure 採樣程序

    • Flush water taps for at least two minutes to remove impurities. 將水龍頭沖洗至少兩分鐘以去除雜質。

    • Disinfect taps following ISO 19458 protocols. 根據 ISO 19458 標準對水龍頭進行消毒。

    • Collect a single 250 ml sterile water sample for microbial tests, covering both Heterotrophic Plate Count (HPC) and E. coli analysis. 收集一個 250 毫升的無菌水樣本，用於微生物測試，包括異養菌群總數（HPC）和大腸桿菌（E. coli）分析。

    • Additional samples are collected for testing physical, chemical, and metal parameters after a 30-minute or 6-hour stagnation period. 另外，在靜置 30 分鐘或 6 小時後，採集其他水樣，用於測試物理、化學及金屬參數。

  2. Acceptance Criteria 接受標準
    Testing ensures the water quality meets the following standards: 測試確保水質達到以下標準：

    • Physical and Chemical 物理及化學參數：

      • Turbidity 濁度: ≤ 3.0 NTU

      • Colour 顏色: ≤ 5 Hazen Units

      • pH 酸鹼值: Between 6.5 and 9.5

      • Free Chlorine 游離氯: ≤ 1.5 mg/L

      • Conductivity 電導率: ≤ 500 µS/cm

    • Metal Content 金屬含量：

      • Lead 鉛: ≤ 10 µg/L

      • Chromium 鉻: ≤ 50 µg/L

      • Nickel 鎳: ≤ 70 µg/L

      • Cadmium 鎘: ≤ 3 µg/L

      • Copper 銅: ≤ 2000 µg/L

      • Antimony 銻: ≤ 20 µg/L

    • Microbiological Standards 微生物標準:

      • HPC 異養菌群總數: ≤ 20 cfu/mL

      • E. coli 大腸桿菌: 0 cfu/100 mL

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How to choose stagnation period (30-minute or 6-hour)?  如何選擇靜置時間 (30 分鐘或 6 小時)?

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  1. 6-Hour Stagnation Period 6小時靜置時間

    • Applicable for 適用對象: New plumbing systems in unoccupied buildings. 新建築物的供水系統，且建築物為未有人居住。

    • Procedure 程序:

      • Flush the tap for at least 2 minutes, then disinfect it. 將水龍頭沖洗至少2分鐘，然後進行消毒。

      • Apply protective measures, such as covering the tap, and let water stagnate for 6 hours before sampling. 採取保護措施（如覆蓋水龍頭），靜置6小時後取樣。

    • Purpose 目的: This extended stagnation period simulates conditions of prolonged inactivity, assessing the potential leaching of metals from the plumbing system. 此靜置時間模擬長期未使用的情況，評估供水系統中金屬釋出的潛在風險。

  2. 30-Minute Stagnation Period 30分鐘靜置時間

    • Applicable for 適用對象: Existing plumbing systems in occupied buildings or village houses. 已有人居住的建築物或村屋的現有供水系統。

    • Procedure 程序:

      • Flush the tap for at least 3 minutes, reinstall the strainer, and disinfect it. 將水龍頭沖洗至少3分鐘，重新安裝濾網後消毒。

      • Let the water stagnate for 30 minutes before sampling. 水靜置30分鐘後取樣。

    • Purpose 目的: This shorter stagnation period reflects typical daily usage patterns, evaluating water quality under regular operating conditions. 此靜置時間反映日常使用模式，評估正常操作條件下的水質情況。

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Criteria for Choosing Stagnation Period 選擇靜置時間的標準
The stagnation period is selected based on the occupancy status of the building:

靜置時間取決於建築物的使用狀態:

  • Unoccupied Buildings: Use a 6-hour stagnation period to assess worst-case scenarios.

      未有人居住的建築物：使用6小時靜置，模擬最壞情況。

  • Occupied Buildings: Use a 30-minute stagnation period to simulate realistic usage and ensure compliance with water quality standards for daily consumption.

      已有人居住的建築物：使用30分鐘靜置，模擬日常使用情況，確保符合飲用水質標準。

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Why Choose Enviro Labs? 選擇 Enviro Labs 的理由?
Enviro Labs offers HOKLAS-accredited testing services that strictly adhere to WSD requirements. Our offerings include:

  • Trained and certified personnel for sampling and testing.

  • Properly documented reports with photographic records for submission.

  • Standard and express turnaround options to fit project timelines.


Enviro Labs 提供獲 HOKLAS 認可的測試服務，嚴格遵守水務署的要求。我們的服務包括：

  • 經過培訓及認證的專業人員進行採樣和測試。

  • 提供帶有照片記錄的詳細報告，便於提交。

  • 標準和加急服務選項以滿足不同項目的時程需求。

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Get Started Today 立即聯絡我們
Ensure your project complies with WSD standards. Contact Enviro Labs for professional water sampling and testing services designed to meet your specific needs. Call us for more information.


確保您的項目符合水務署標準。聯絡 Enviro Labs 獲取專業的水質採樣與測試服務。我們樂意提供更多資訊，歡迎致電查詢！

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​References 參考資料

1. WSD Circular Letter No. 5/2023

   水務署通函第5/2023號

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