(References in parentheses are to the Risk Information Table.) 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: DWSNZ Drinking-Water Standards for New Zealand – Preventive measures Checking preventive measures Corrective action Causes What to check Signs that action is needed Event: INTRODUCTION OF CONTAMINATION BY PRESSURE FLUCTUATIONS Possible hazards: Germs and chemical determinands (depending on the nature of the contamination source). Level of risk: High1 D2.2.1.1 Model network analysis to Flows. Increase in Revisit identify potential problem flow above network Mains Pressures. pressure areas. normal to identify pressure Demand. rates. potential failure Regular on hydrant problem areas Treatment elsewhere, flows or correlation of fire Pressure better. plant output. or high service data with water fluctuations. supplier’s pressure and Review Reservoir demand. flow data. pumping quality. levels regime out of Planned replacement outside zone. and/or relining of mains. normal diurnal Review Develop programmes to pattern. replacement carry out annual leak programme. detection and undertake E. coli or repairs. Record: coliforms Ensure detected in backflow customer complaints 100 ml water valves are fire service feedback. sample. installed at properties Implement water and audited to conservation policy eg, – assess correct restrictions on garden operation (see watering, public appeals Guide D2.4). to reduce demand. Modify water Increase flow rate of conservation treatment plant. strategy. Drop the pressure in the whole system or part of it. 1 Low pressure can back-siphonage. Preventive measures Checking preventive measures Corrective action Causes What to check Signs that action is needed INTRODUCTION OF CONTAMINATION BY PRESSURE FLUCTUATIONS cont’d
(References in parentheses are to the Risk Information Table.) 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: DWSNZ – Drinking-Water Standards for New Zealand Causes Preventive measures Checking preventive measures Corrective action What to check Signs that action is needed Event: INTRODUCTION OF CONTAMINATION BY PRESSURE FLUCTUATIONS Possible hazards: Germs and chemical determinands (depending on the nature of the contamination source). Level of risk: High1 D2.2.1.1 Mains pressure failure elsewhere, or high demand. Model network analysis to identify potential problem pressure areas. Regular on hydrant flows or correlation of fire service data with water supplier’s pressure and flow data. Planned replacement and/or relining of mains. Develop programmes to carry out annual leak detection and undertake repairs. Record: customer complaints fire service feedback. Implement water conservation policy – eg, restrictions on garden watering, public appeals to reduce demand. Increase flow rate of treatment plant. Drop the pressure in the whole system or part of it. Flows. Pressures. Demand. Treatment plant output. quality. Increase in flow above normal rates. Pressure fluctuations. Reservoir levels outside normal diurnal pattern. E. coli or coliforms detected in 100 ml water sample. Revisit network to identify potential problem areas better. Review pumping regime out of zone. Review replacement programme. Ensure backflow valves are installed at properties and audited to assess correct operation (see Guide D2.4). Modify water conservation strategy. 1 Low pressure can back-siphonage. Causes Preventive measures Checking preventive measures Corrective action What to check Signs that action is needed INTRODUCTION OF CONTAMINATION BY PRESSURE FLUCTUATIONS cont’d
distribution-system-pressure-feb14-v2.docx