PRESSURE IS REDUCED IN THE WATER MAIN
The water supply system is designed to ensure that water flows to your property under pressure. If this pressure is not maintained, there is a chance that water could be drawn back into Yarra Valley Water’s water supply system from a customer’s premises. Water pressure can be affected when:
• there is a break in the water main
• water is being pumped from the main water supply during a fire.
• a customer is using water at a higher pressure than the pressure supplied by Yarra Valley Water
• heavy water use on site reduces water pressure within Yarra Valley Water’s supply network.
• the water outlet on the property is higher than the water main.
THERE IS A CROSS CONNECTION BETWEEN THE DRINKING WATER SUPPLY AND A CONTAMINATED SOURCE
There is a risk to public health if there is a cross connection between your water supply and a contaminated source. If there is a drop in pressure in the water main, a vacuum could be created in the water supply system. Under certain conditions this draws liquid from a potentially contaminated source back into the drinking water supply.
Some examples of cross connections where a backflow incident can occur are:
• in metal processing or chemical plants where metals in solution or chemicals used for production can come into contact with the water supply.
• in market gardens, where chemical injectors, irrigation systems and garden hoses are connected to the water supply.
• when a hose is left running in a container with chemicals such as fertilisers.
• car wash facilities, where there is a connection between the scrubber and rinse cycles.
• pipe work that allows recycled water to enter the drinking water supply.
Cross-connections can occur in a number of industries.
• Chemical plants
• Metal processing plants
• Pest controllers
• Paint manufacturers
• Market gardens
• Golf courses or sporting ovals
• Caravan parks.
A NEARBY PROPERTY USES THE WATER SUPPLY
A dangerous chemical (or contaminant), may get into the water mains and into a nearby property. When this water is used, the occupants could be seriously or fatally injured.
CONTAMINATED WATER SUPPLY
In late 2003, residents of an area in Coventry, England were warned not to drink or cook with tap water for several days. A local business accidentally contaminated the water supply with a fertiliser product that took many hours and thousands of litres of water to clean the water main of the contaminant.
WHY DO I NEED TO INSTALL A BACKFLOW PREVENTION DEVICE AT THE MAIN METER?
A backflow incident can cause health concerns for people using the water supply. A backflow prevention device installed at the main meter ensures that the drinking water supplied by Yarra Valley Water cannot be contaminated. Different types of devices if there is a cross connection can be installed depending on the hazard rating and of the processes carried out on the property.
THE THREE HAZARD RATINGS IDENTIFIED BY THE NATIONAL PLUMBING AND DRAINAGE CODE AS/NZS 3500:1 SECTION 4 ARE:
• high hazard – any condition, device or practice which in connection with the water supply system has the potential to cause death
• medium hazard – any condition, device or practice which in connection with the water supply could endanger health
• low hazard – any condition, device or practice which in connection with the water supply system would constitute a nuisance but not endanger health.
As processes differ within each business, you will need to consult an accredited backflow prevention plumber to determine your hazard rating and the type of backflow prevention device required at the main meter.
Melbourne Backflow Prevention Group is a member of the Melbourne Plumping Group.