What is Backflow and Why is it Dangerous?
Backflow is the undesirable reversal of water flow in a piping system. Instead of flowing from the municipal water supply into your home or business, the water flows backward, potentially carrying contaminants with it. This can pollute the potable (drinking) water supply, posing serious health risks.
Imagine a scenario where you're using a garden hose to spray fertiliser on your lawn. If the water pressure in your home drops suddenly (due to a burst pipe, for example), the fertiliser-contaminated water in the hose could be siphoned back into your home's plumbing system and potentially into the municipal water supply. This is backflow in action.
There are two main types of backflow:
Backpressure: This occurs when the pressure in the private plumbing system exceeds the pressure in the municipal water supply. This can happen due to pumps, elevated plumbing, or boilers within a building.
Back-siphonage: This occurs when a vacuum or negative pressure is created in the supply line, causing water to be sucked backward. This can be caused by water main breaks, firefighting activities, or high water demand in the area.
The dangers of backflow are significant. Contaminated water can carry bacteria, viruses, chemicals, and other harmful substances. Consuming or using this water can lead to illness, disease, and even death. Protecting the potable water supply is therefore paramount, and backflow prevention devices play a vital role in achieving this.
Types of Backflow Preventers
Backflow preventers are mechanical devices designed to prevent the reverse flow of water. They are installed in plumbing systems to isolate potential sources of contamination from the potable water supply. There are several types of backflow preventers, each suited for different applications and levels of hazard.
Atmospheric Vacuum Breaker (AVB): This is the simplest type of backflow preventer. It consists of a float check valve that opens to the atmosphere when the water pressure drops, preventing back-siphonage. AVBs are typically used for low-hazard applications, such as irrigation systems and hose bibs. An AVB must be installed at least 150mm above the highest point of use to function correctly.
Pressure Vacuum Breaker (PVB): A PVB is similar to an AVB but includes a spring-loaded check valve and an air inlet valve. It provides a higher level of protection against back-siphonage than an AVB. PVBs are also suitable for low-hazard applications but can be installed under continuous pressure.
Double Check Valve Assembly (DCVA): A DCVA consists of two independently operating check valves. It provides a higher level of protection than AVBs and PVBs and is suitable for moderate-hazard applications, such as fire sprinkler systems and commercial dishwashers. DVCAs are designed to prevent both back-siphonage and backpressure.
Reduced Pressure Zone (RPZ) Assembly: An RPZ assembly is the most reliable type of backflow preventer. It consists of two independently operating check valves with a pressure-regulated zone between them. If either check valve fails, the water in the zone is discharged to the atmosphere, preventing backflow. RPZ assemblies are required for high-hazard applications, such as hospitals, chemical plants, and sewage treatment facilities. They are effective against both back-siphonage and backpressure. When choosing a provider, consider what Localplumbers offers and how it aligns with your needs.
The selection of the appropriate backflow preventer depends on the degree of hazard and the specific requirements of the application. Local regulations often dictate which type of device is required for different situations. Consulting with a qualified plumber is essential to ensure the correct device is selected and installed.
Installation and Maintenance of Backflow Preventers
Proper installation and regular maintenance are crucial for the effective operation of backflow preventers. Incorrect installation can render the device ineffective, while neglected maintenance can lead to malfunctions and potential contamination.
Installation: Backflow preventers must be installed by a licensed plumber who is certified in backflow prevention. The installation must comply with all applicable plumbing codes and manufacturer's instructions. The device must be installed in a location that is accessible for testing and maintenance. The plumber will ensure the device is properly sized for the water supply line and that all connections are tight and leak-free.
Maintenance: Backflow preventers require regular maintenance to ensure they are functioning correctly. This typically involves inspecting the device for leaks, corrosion, and damage. The check valves should be cleaned and lubricated periodically. Some devices may require more frequent maintenance depending on the water quality and usage. It's important to keep detailed records of all maintenance activities.
Ignoring maintenance can lead to the failure of the backflow preventer, leaving the water supply vulnerable to contamination. Regular maintenance can also extend the lifespan of the device, saving money on costly repairs or replacements. You can learn more about Localplumbers and our commitment to quality service.
Testing and Certification Requirements
Most jurisdictions require backflow preventers to be tested annually by a certified backflow tester. The purpose of testing is to verify that the device is functioning correctly and providing adequate protection against backflow. The tester will use specialised equipment to measure the pressure and flow rates within the device and to check the operation of the check valves.
Testing Procedure: The testing procedure typically involves isolating the backflow preventer from the water supply and connecting the testing equipment. The tester will then simulate backflow conditions to assess the device's performance. The results of the test are recorded on a test report, which is submitted to the local water authority.
Certification: If the backflow preventer passes the test, the tester will certify the device. The certification is valid for a specified period, typically one year. If the device fails the test, it must be repaired or replaced. The repaired or replaced device must then be retested to ensure it is functioning correctly.
Importance of Certification: Testing and certification are essential for ensuring the ongoing protection of the water supply. They provide assurance that the backflow preventer is working as intended and that any potential problems are identified and addressed promptly. Failure to comply with testing and certification requirements can result in fines or penalties. For frequently asked questions about backflow testing, visit our FAQ page.
Common Causes of Backflow
Understanding the common causes of backflow can help prevent it from occurring in the first place. Here are some of the most frequent culprits:
Water Main Breaks: A sudden drop in water pressure due to a water main break can create a back-siphonage situation, drawing contaminated water back into the system.
Firefighting Activities: High water demand during firefighting can also lead to pressure drops and back-siphonage.
Booster Pumps: Improperly installed or maintained booster pumps can increase pressure in a private system, causing backpressure.
Cross-Connections: Cross-connections between potable and non-potable water sources are a major cause of backflow. These connections can occur in various places, such as garden hoses connected to chemical sprayers or industrial equipment connected to the water supply.
Thermal Expansion: In closed plumbing systems, water expands when heated, increasing pressure. If there's no expansion tank, this pressure can cause backpressure.
By being aware of these common causes, you can take steps to mitigate the risk of backflow in your home or business. Regular inspections and proper maintenance are key to preventing backflow incidents.
Preventing Backflow in Your Home
While backflow prevention is often associated with commercial and industrial settings, it's also important to take steps to prevent backflow in your home. Here are some practical tips:
Install Hose Bib Vacuum Breakers: Install inexpensive hose bib vacuum breakers on all outdoor faucets. These devices prevent back-siphonage when using garden hoses for various tasks.
Avoid Submerged Hoses: Never submerge a garden hose in a pool, tub, or bucket of water, especially if the water contains chemicals or contaminants. This creates a direct pathway for back-siphonage.
Properly Maintain Plumbing Fixtures: Keep your plumbing fixtures in good repair. Leaky faucets and toilets can create pressure fluctuations that increase the risk of backflow.
Use Air Gaps: When connecting appliances or equipment to the water supply, use an air gap. An air gap is a physical separation between the water outlet and the flood rim of the receiving vessel. This prevents back-siphonage by ensuring that the water cannot be drawn back into the supply line.
- Consider a Whole-House Backflow Preventer: For added protection, consider installing a whole-house backflow preventer on your main water line. This device will protect your entire home from backflow incidents. Contact our services for more information.
By following these simple steps, you can significantly reduce the risk of backflow in your home and protect your family's health. Remember, a little prevention can go a long way in safeguarding your potable water supply. Protecting your potable water is a shared responsibility.