Risk Information Table Reliable information about water quality is essential for the proper management of a water supply. Knowledgeable and skilled staff are also essential for minimising the public health risks associated with water supplies. Please read the staff training (Guide and the G1) monitoring guides (Guide While we haven’t pointed out every detail of how these G2). documents are linked with the present document, the links are many and are important. Abbreviations: MAV Maximum acceptable see Drinking-Water Standards for New Zealand:2000 – – Preventive measures Checking preventive measures Corrective action Causes What to Signs that action is needed Event: WATER PRESSURE IN THE DISTRIBUTION SYSTEM LOWER THAN PRESSURE IN SUPPLIED PREMISES Possible hazards: Germs; chemical determinands. Level of risk: High D2.4.1.1 Installation of one of Testing and Reports by Determine the following inspection consumers of reasons for A pressure drop backflow prevention records. gross low system in the devices depending pressure and reticulated on the of risk to of tapwater. rectify if system. quality. the supply:1 possible. Unexplained Chemical reduced pressure fluctuations in Identify the determinands backflow chemical and premises from (when there is prevention device which reason to water quality. backflow non-testable suspect occurred and double check contamination E. coli or install valve coliforms appropriate detected in testable double device (see 100 mL water check valve D2.4.2). sample. air gap. Annual inspection of targeted and testing of chemical backflow prevention determinands devices. are more than 50% of their MAV. D2.4.1.2 See D2.4.1.1. See D2.4.1.1. Identify the premises from An elevated which pressure in the backflow premise(s) occurred and supplied as install compared to the appropriate reticulated device. system. 1 See Risk Assessment Table. Preventive measures Checking preventive measures Corrective action Causes What to check Signs that action is needed
Risk Information Table Reliable information about water quality is essential for the proper management of a water supply. Knowledgeable and skilled staff are also essential for minimising the public health risks associated with water supplies. Please read the staff training (Guide G1) and the monitoring guides (Guide G2). While we haven’t pointed out every detail of how these documents are linked with the present document, the links are many and are important. Abbreviations: MAV – Maximum acceptable – see Drinking-Water Standards for New Zealand:2000 Causes Preventive measures Checking preventive measures Corrective action What to Signs that action is needed Event: WATER PRESSURE IN THE DISTRIBUTION SYSTEM LOWER THAN PRESSURE IN SUPPLIED PREMISES Possible hazards: Germs; chemical determinands. Level of risk: High D2.4.1.1 A pressure drop in the reticulated system. Installation of one of the following backflow prevention devices depending on the of risk to the supply:1 reduced pressure backflow prevention device non-testable double check valve testable double check valve air gap. Annual inspection and testing of backflow prevention devices. Testing and inspection records. quality. Chemical determinands (when there is reason to suspect Reports by consumers of gross contamination of tapwater. Unexplained fluctuations in chemical and water quality. E. coli or coliforms detected in 100 mL water sample. of targeted chemical determinands are more than 50% of their MAV. Determine reasons for low system pressure and rectify if possible. Identify the premises from which backflow occurred and install appropriate device (see D2.4.2). D2.4.1.2 An elevated pressure in the premise(s) supplied as compared to the reticulated system. See D2.4.1.1. See D2.4.1.1. Identify the premises from which backflow occurred and install appropriate device. 1 See Risk Assessment Table. Causes Preventive measures Checking preventive measures Corrective action What to check Signs that action is needed
distribution-backflow-prevention-feb14-v2.docx