Backflow prevention - Back to basics

Backflow valves are being installed everywhere these days. It’s good business and protection for our water supplies, but plumbers need to be aware of the pitfalls, offer professional advice to their customers, and keep up to date with best practices.

Australian Standards and regulations in many areas require installation of backflow prevention valves to protect our potable water supplies. The benefits cant be seen or felt by customers, and they’re viewed as nothing more than an added cost. This has been a limiting factor in their acceptance. Thanks to many water authorities and councils, the implementation of backflow prevention policies for retrofit and new installations has opened a window to improve product competition and development, value-added services and water conservation.

Proper selection and installation of backflow prevention devices ensures ease of annual maintenance for plumbers, and protection of the customer s’ interests. When cost might be the deciding factor, a professional plumber should offer information and a range of options to the customer.

Investigate the water situation

Containment backflow devices are typically installed at the outlet of water meters and for many customers this is the first exposure to backflow prevention. While the registration and testing procedures vary in different areas, one common requirement is that medium and high hazard devices should be tested annually to comply with AS/NZS 3500.

Plumbers involved in installation, testing and annual maintenance of backflow devices have a ground floor opportunity to display their professionalism by properly investigating the water supply, and providing value added services. Even if the customer contact is only once a year to service a backflow device, a positive contact experience can lead to additional work and long-term customer relationships.

Here are some simple suggestions:-

Some major industrial and commercial water users have barely enough water to begin with, and backflow devices reduce water pressure. In addition, some industries have water needs that are critical to their business, and professional advice from a plumbing consultant can be a small cost to achieve the best outcome. Plumbers planning to retrofit backflow devices can suggest to their customers the option of employing a plumbing consultant to investigate the available water supply and customer water requirements. These investigations can involve pressure and flow data logging. They can reveal restrictions and pressure fluctuations, and can provide information for metering changes, new tappings, piping alterations and selection of appropriate backflow devices. Plumbers offering this option are placing their customers in an informed position to make decisions that best suit their needs.

There are a number of backflow devices being installed on fire / fire and general water services without any follow-up verification of the performance of fire services. Prior to installing backflow devices on fire services, plumbers should inform their customers of the requirement to have the fire services performance tested and certified after installation. Local requirements vary, so consult your local fire authority.

The annual testing of a containment backflow device requires shut down of the water supply. Unless there is more than one supply to the property, this can involve interruption of the water supply to industrial and commercial properties and it’s an ideal opportunity to look at the water meter. If the customer tells you that the water is off, but water continues to pass through the meter, it’s reasonable to wonder where it’s going. We’ve seen many instances of leaking water services, sticking float valves, leaking t & p.r. valves etc, and customers are always pleased to hear about these issues to save water and reduce their water bill.

Make the assembly easy to service

Backflow prevention devices need to be serviced annually. The best time to make the future annual service work easy is at the time of installation.

Tips for easy maintenance and testing of backflow devices:-

Some parts fail over time apart from the backflow device, such as line strainer element and downstream check valve. It’s best to install union connections or flanges in the backflow device assembly to facilitate easy removal.

Many backflow devices are installed in public areas. Theft and vandalism can be a problem. Customers should be offered the option of having locked upstream and downstream isolation valves, or a lockable protective cage. Test cocks are a common target, and devices should be installed in protective cages, particularly in schools and shopping centres.

It can be extremely difficult to access strainer elements from “Y” strainers in pits. While strainers should face downward in normal situations, it is preferable to face them upward in pits. After removing the element, the upstream isolation valve can be opened slightly to flush out any debris. Another option is to install upstream isolation valves that incorporate a line strainer that is accessible from the top.

Backflow devices being installed in pits should ideally be of a type that are accessible for servicing from above.

Line strainers on backflow device assemblies under 50 mm are generally manufactured of brass. The regular tightening of brass caps on line strainers can place stress on the short brass thread and after many services, the thread strips. It is preferable to install strainers incorporating an “o” ring cap seal, because very little tightening pressure is required, and stress on the cap thread is minimal.

A number of backflow device manufacturers are now supplying devices with attached male test fittings. Test kit hoses screw right onto these fittings without the need for teflon tape. Some manufacturers are also selling quick test fittings that have an “o” ring. These newer devices and quick test fittings make the annual service a breeze.

Testing and maintenance

AS/NZS 3500.1:2003 states that, “Where the device (backflow device) is fitted with test taps, their location shall ensure the clearance necessary for the performance of the applicable test procedure and maintenance as defined in AS/NZS2845.3”

It’s also important to note that AS 2845.3 requires that, “Test equipment used for the field testing of backflow prevention devices shall be annually calibrated and certified by a registered laboratory to Appendix I”

It is recommended that backflow prevention testers include the details of their test equipment and last certification date on test reports. This provides some assurance to customers, water authorities and councils that the accuracy of test results is valid.

Plumbing Consultant, Peter Wenning, has a background in plumbing, plumbing inspection and water utility contract management roles in metering and backflow prevention programs. Peter can be contacted at pwenning@bigpond.com.