One of the biggest risks to our water supply is from backflow caused when water pressure drops in the water distribution system. When backflow occurs, water can flow in the opposite direction from residential or commercial premises back into the public water supply network. Contaminants could be back-siphoned or injected by back-pressure into the public water supply.

A back-siphon occurs due to a loss of pressure in the public water distribution system. This can occur when large volumes of water are being drawn for fire protection or during a water main or plumbing system break or during a shut down of a water main or plumbing system for repair.

During a back-siphon, a reduction of pressure creates a vacuum in the piping and the water flows in the reverse direction. For example, if a hose tap is open when the end of the hose is submerged in a contaminated container of water, the contaminated water in the container is siphoned into the premises plumbing and back into the public water supply.

Back-pressure occurs when water is being pumped at a pressure higher than, the town mains or pressure within the building.

When backpressure occurs, water flows in the reverse direction to normal flow. For example, if a pump supplying water from a non-drinkable source, such as a landscape pond, is accidentally connected to the plumbing system, the contaminated water can be pumped back into the drinking water supply. It is important to understand that, when coupled with a reduction in mains water pressure, the water source only needs to be slightly elevated above the public water supply pipe pressure to push the water back through the premises into the water mains.

Because both homes and businesses use chemicals and other potential contaminants, backflow can be a major threat to the health and wellbeing of you, your friends, family and workmates. At It’s worst, backflow contamination of the water supply could cause death or serious injury, so we all have a responsibility to help reduce this risks.