There are multiple types of backflow preventers. The three most common are the pressure vacuum breaker (PVB), the reduced pressure zone (RPZ), and the double check assembly (DCA). These are all installed in the water system immediately after the isolation valve. There is a fourth backflow preventer which is also fairly common. The atmospheric vacuum breaker (AVB) is installed in each zone of the sprinkler system. After that, it immediately follows the zone control valve. Each type of backflow device is designed to provide a different level of protection for varying commercial or residential applications. For example, hospitals and morgues, which handle large quantities of hazardous wastes on a daily basis, require much heavier-duty backflow preventers than a residential irrigation system. Show Several factors must be taken into consideration when selecting a backflow device. These include local building codes regulating backflow preventers, the size of the landscape to be irrigated, and where the backflow preventer is going to be installed. It’s a good idea to familiarize yourself with the different types of backflow devices. It will help you to select the one that best meets your requirements. The first Type Of Backflow Preventer Is The Pressure Vacuum BreakerPressure vacuum breaker assemblies (PVB) are the most common, inexpensive type of whole-system backflow preventer. It consists of an inlet shutoff valve at the bottom, a single valve body consisting of a pressure vacuum breaker, a check valve, two test cocks, and an outlet shutoff valve. As well as being inexpensive, PVBs are relatively simple in design and are easy to install, maintain and repair. Some pressure vacuum breakers also offer built-in freeze protection; however, this only protects the PVB assembly. Inlet and outlet pipes can still freeze if the system isn’t properly winterized. One of the downsides of PVBs is that they will occasionally eject some water. Choose a “spill-resistant” model of PVB for indoor installations or any time spillage would create a nuisance. An air gap drain is also required if the valve is installed in a basement or other interior space. Pressure Vacuum Breaker Assemblies:
The Second Type Of Backflow Preventer Is The Double Check ValvesDouble check valves (DCV, also called double check assemblies or DCA) are a good choice for underground or indoor installations. A DCA consists of an inlet shutoff valve, two independently operating spring-loaded check valves (usually inside a single valve body), four test cocks, and an outlet shutoff valve. If local building codes allow for it, you must install Double check assemblies vertically.  The DCA is the most common type of approved backflow prevention device for use in underground or in-line installations. In-line (or below-grade) simply means that the backflow device is parallel with the piping of the sprinkler system; unlike the PVB, the DCA does not have to be installed 12 inches above the highest point in the system. Some areas do require above-ground installation, so check with local authorities before installing below ground. It is possible to build a double check valve assembly from new components, but this is not the best option as there is a high risk of built assemblies not meeting local code. A better option, for convenience, cost-effectiveness, and coding restrictions, is to purchase a pre-assembled double check valve assembly. Double Check Valve Assemblies:Installed either above ground or inline (underground) Do not use with chemigation May be installed horizontally or vertically, but horizontally is preferred May be installed where the potential for back-siphonage or backpressure is present. The Third Type Of Backflow Preventer Is The Reduced Pressure Zone AssemblyReduced pressure zone assemblies (RPZ), also sometimes called a reduced pressure principle assembly, is the most complex and expensive backflow preventer. However, when working properly, RPZs are the most secure and reliable of all backflow prevention devices. A reduced pressure zone assembly consists of an inlet shutoff valve, two independently operating spring-loaded check valves separated by a pressure differential relief valve, four test cocks, and an outlet shutoff valve. Some localities, such as Honolulu, do not allow reduced pressure zone assemblies to be installed below grade in underground lawn sprinkler systems, while others require copper pipes on both ends of the assembly. Local codes may be especially variable and stringent on reduced pressure zone assembly, so have a thorough understanding of local requirements before proceeding. The image above shows the Febco 825Y Reduced Pressure Zone Backflow Preventer. Shop for this and other backflow preventers at SprinklerWarehouse.com. Reduced pressure zone assemblies come in a variety of configurations. Choose an “inline” or “straight” configuration for installation underground. For above-ground installation, consider an “n” configuration assembly for a very small footprint. Reduced Pressure Zone Assemblies:
Atmospheric Vacuum Breaker (Anti-Siphon) Atmospheric vacuum breakers (AVB) are the simplest and least expensive backflow preventers for one or two-zone irrigation systems. An AVB must be installed on the pipe directly after every control valve, so for systems with more than about six control valves, AVBs are not cost-effective. AVBs are also the least reliable and least often recommended. Most large cities and suburbs do not allow the use of atmospheric vacuum breakers in lawn sprinkler systems. Do not use AVBs in areas of constant pressure. This includes where shutoff valves would be located downstream where there is a potential for back pressure, or on any system that incorporates chemigation techniques. Atmospheric Vacuum Breaker Assemblies:
At Green Planet Plumbing we have found that many of our customers are unfamiliar with the problem of backflow. They unsure why and how it needs to be prevented, how backflow prevention testing works, and who can install, commission and test backflow prevention devices. With this in mind, we have compiled this blog to answer all the questions you never knew you had about ‘backflow prevention’. What is Backflow?Backflow refers to the unintended reverse flow of water from a property back into the drinking water supply. Backflow can occur if there is a drop in water pressure or the water pressure on a property is higher than the pressure at the water main, or via cross connections in a user’s premises and is considered a serious issue because it can result in used or potentially contaminated water entering the supply of drinking water. What controls are in place for Backflow Prevention?To safeguard public health and protect drinking (potable) water stores and its supply system, there are several controls in place to prevent backflow, including the requirement for backflow prevention devices being fitted to a sites’ connection to the water supply system. The requirements for backflow prevention are set out in various laws, regulations, and standards, which may differ from one region to another, depending on the water supply authority. When designing and building premises that are connected to mains water, the water supply authority generally requires that the plumber, building consultant or property owner complies with the backflow prevention measures set down in one, or all, of the following documents: What is a Backflow Prevention Device?Every property that is connected to mains water is required to have an appropriate site containment backflow prevention device installed and maintained at the property’s boundary, immediately downstream of the property’s water meter. Backflow prevention devices must not be buried underground or installed in a chamber or pit – rather they should be easily accessible, to allow proper testing and maintenance. The backflow prevention device is fitted to the mains fresh water supply pipe, generally on the water meter, to stop used or contaminated water flowing back into the water supply system. Backflow prevention typically utilises one of three methods:
There many kinds of backflow prevention devices within these categories, including:
Which Backflow Prevention Device do I need?The hazard rating determines the level of backflow protection device required. Many water authorities require that properties connected to their water infrastructure be inspected by an accredited person, risk assessed, and assigned a site containment hazard rating – low, medium, or high hazard. The backflow plumber who installs and commissions the backflow prevention device must advise the property owner of the property’s backflow prevention requirements, install a backflow prevention device appropriate to the property’s hazard rating and advise the property owner of the maintenance and testing requirements for the device that has been fitted. The team here at Green Planet Plumbing are able to fit and test backflow prevention systems for you. What is Backflow Testing?Backflow testing is the testing carried out on backflow prevention devices installed to properties with medium to high risk hazard ratings. Initial testing is carried out when the device is first installed and commissioned for use, and then annually thereafter to confirm the device is operational and complies with AS2845. Backflow devices are not infallible – they contain seals, valves and moving parts that are subject to wear and fatigue. Testing that the device is operating as intended is an important part of backflow prevention, along with checking that all water in the home is running in the right direction. When testing your backflow prevention system, your accredited plumber will:
Please note that the customer is responsible for ensuring the site containment backflow prevention device is properly maintained and, where a medium or high hazard backflow device has been installed, is required to have the device routinely tested on an annual basis. Who can install Backflow Prevention Devices?Many smaller water meters, appropriate for installation at properties with a low hazard rating, are fitted with a simple, non-testable backflow prevention device (generally a dual check valve that is incorporated in the water meter). These simple backflow prevention devices may be installed by a licensed plumbing company, such as Green Planet Plumbing. Larger water meters usually require a separate backflow device to be fitted by a licensed plumber or plumber with backflow prevention accreditation issued by a registered training organisation (a ‘backflow plumber’). Only accredited backflow plumbers are authorised to test and commission backflow prevention devices and to submit an approved test certification report with the water supplier, to verify that the device is effective. Properties with an unmetered water connection must have a backflow prevention device appropriate to the property’s hazard rating installed and maintained by a licensed plumber at the point of connection to the water main (at the property boundary). Those properties with medium or high hazard backflow prevention devices installed to their unmetered water connection must be checked by an accredited backflow plumber annually. Who can commission and test Backflow Prevention Devices?After installation, a testable backflow prevention device must be commissioned and certified by an accredited backflow plumber within seven days, and the accredited plumber who initially tests and commissions the device must submit the test results to the local water authority. Following installation and commissioning, the device must be tested annually by an accredited backflow compliance plumber. The results of these annual tests must be submitted to, and registered with, the local water authority, to confirm that the device is operational and compliant with the local water authority’s Site Containment Backflow Prevention Standard and Australian Standard AS2845.3:1993. Green Planet Plumbing have an unbeatable reputation as Newcastle’s most environmentally friendly plumbers, with timely and reliable service and the highest standards of workmanship. Our licensed plumbers and accredited backflow compliance testers are here to help you meet all your backflow prevention and testing requirements. Green Planet also offer a wide range of plumbing and home maintenance services – check out our Services page for more information! For peace of mind knowing that you are getting the best (and greenest) backflow prevention and testing services in Newcastle, contact Green Planet Plumbing Newcastle today by calling 02 4911 9402. Alternatively, send an email to or complete our Enquiry form and one of our friendly team members will contact you back. |
What is the most reliable form of backflow prevention device?
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