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Plumbing Overview: 4 Types of Backflow Prevention Systems

Residential and commercial plumbing systems are prone to many day-to-day problems such as leaks, blocks, low water pressure, and backflow. These plumbing issues can start small, but if they aren’t attended to immediately, there’s a big chance they will evolve into major problems. These repairs would then be complex and expensive to fix.

How Do Backflows Happen?

When it comes to the main water supply line in your home or workplace, potable water should only flow in one direction toward the building. However, pressure changes and other issues within the pipes can cause contaminated water from nearby irrigation systems and sewers to flow backwards into the supply line.

For example, a break in the water main can cause a pressure vacuum in the local plumbing system. Groundwater from a nearby irrigation system can then be pulled into the water system shared by the community, which leads to contaminants in water used for drinking, hygiene, cooking, and other daily functions. 

When backflow occurs, your potable water supply is contaminated with human waste, chlorine, cleaning solution residue, fertilisers, and many other dangerous substances. Backflow prevention is crucial because the ingestion of these contaminants can lead to severe illnesses and even death. 

How Can Backflow Be Prevented?

Backflow prevention devices allow water to flow only in the right direction. They are installed on residential and commercial water pipes and act as a one-way gate for your water supply. They enable water to flow into the house or building and block it if it tries to divert back into the public water supply. These devices are crucial in preventing the contamination of potable drinking water.

Low-hazard buildings and residences are the sources of pollutants that do not pose a health hazard. In contrast, high-hazard industries use contaminants that are dangerous to the public. Legal standards and local regulations set standards for all backflow prevention systems in residential, commercial, and industrial properties connected to the drinking water supply.

There are four types of backflow prevention devices, and each of them provides different levels of protection. 

  1. Atmospheric Vacuum Breaker (AVB): These breakers use the most basic form of protection against backflow: the gap of air between the contamination source and the water system. This relatively simple device consists of a check valve member and a closed air vent.
  2. Double-Check Valves (DCVs): These valves are used in properties that regularly use low-toxicity substances such as commercial disinfectants and cleaners. DCVs have an upstream shut-off valve, two spring-loaded control valves, four test cocks, and a downstream shut-off valve.
  3. Double-Check Detector Assembly: They work hand in hand with DCVs, and are generally used for fire line installations. It is also used to prevent the backflow of non-health hazards.
  4. Reduced Pressure Zone Device: These are the backflow prevention devices used in high-hazard commercial and industrial properties such as sewage treatment plans, hospitals, and gas production warehouses.


Backflow occurs when pressure changes in the local water line cause contaminated water to flow into houses and hospitals. Fortunately, local regulations mandate that backflow prevention systems be installed in every property connected to the potable water supply. However, if you aren’t sure about your backflow prevention system’s condition, contact local plumbers for an inspection.

If you’re looking for plumbing services on the Sunshine Coast, Sunny Coast Plumbing and Gas is the best choice for you. We provide preventative plumbing maintenance for residential and commercial properties. For high-quality maintenance, repairs, installation, and inspection, contact us today!

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