File images, USA 2007

Advertisement, Santa Cruz Sentinel, April 2007

Fire Protection, Backflow Prevention Frost Protection, Auburn California, April 2007










PVB center median strip, Santa Cruz California, May 2007

RPZD center median strip, Santa Cruz California, May 2007

Backflow Incident - Melbourne

An incident occurred at a Melbourne Service Station, where car wash waste water and sewer was drawn into the internal potable water supply system.

Due to a blockage in the sewerage system, sewer backed up and filled a car wash below ground recirculation tank. At the same time the water supply had been turned off at the meter -apparently as a prank.

Arriving on a Saturday morning with an anticipated rush of car wash customers, the service station attendant immediately opened the car wash and turned on the pumps.
As usual, the pumps were started by priming with water from the mains supply.
With some difficulty in priming the pumps, the operator left the supply on, and opened other areas for business.

With the arrival of cars to the car wash, the pumps appeared to be operating and so business continued throughout the morning. At the same time there was water at the tap outlets, and there was no indication that the main supply had been turned off.

At around lunchtime, a customer complained that the water from a tap at the petrol filling area had a “funny smell and taste”. The attendant was busy, but a few more complaints from customers raised the attendants concerns, who then checked the problem and called a plumber. The plumber resolved the problem on Saturday evening by turning on the water at the meter, unblocking the drains and fitting a check valve to the pump priming line.

It appears that throughout Saturday, there was enough waste water to run the car wash and, pump waste water back through the potable water supply system. Of course water for flushing toilets was being recycled, entering the drainage system, recirculation tanks and back into the potable supply lines.
Equipment connected to the potable water supply system included taps at petrol filling areas which could have been used to fill customers drink containers, a coffee machine and flavoured ice machine.

Concrete lined ductile iron backflow assy - Mornington Peninsula

New assembly
In progress
Before

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.

Wilkins visit - Paso Robles, California

In March 2003, we visited the Wilkins factory in Paso Robles, California.
Images posted for interest.

Testing and more testing

Backflow prevention test rig

Setting up new demonstration trailer

Backflow Prevention Programs - A Wholistic Approach

Protection of the water reticulation system requires a wholistic management approach. Backflow prevention and cross connection control is one part of that wholistic approach.

Here we look at one project, and the “closed” system objective, and some features of a good backflow prevention program.

A major steel manufacturer on the Mornington Peninsula recently completed reconstruction of its water meter stations. The project took three years of planning, design and construction to ensure no loss of production, and seamless shut down.

South East Water requested installation of backflow devices at five water meter stations as part of its’ containment backflow prevention program. The water had not been shut down for 20 years. The steel piping was deteriorating, and this presented a perfect opportunity to exchange the water meters and replace the old valves and piping.

From a plumbing perspective, the project was interesting because there are few above ground ductile iron water meter assemblies of 200 to 375 mm in size for fire and general water. The piping was replaced with flanged piping spools constructed of cement lined ductile iron to provide a heavy duty, impact resistant solution capable of withstanding high thrust and pressure.

One of the critical issues was to keep pressure losses to a minimum. This was achieved by removing the old meter valves, check valves and above ground steel piping. The internal diameter of old steel piping had reduced significantly due to the build up of rust and scale.

Reduced Pressure Zone backflow prevention devices were installed. This type of device can reduce the pressure by as much as 100 kPa. It was important to select backflow valves with low head loss characteristics, and after comparing a number of products; the Wilkins Model 375 was selected. The valve head loss is around 65 kPa at 75 litres/second.

At the same time, there was an increase in supply pressure. An open reservoir was decommissioned and supply was then from an adjacent reservoir of higher elevation and this resulted in a pressure increase of 50 to 60 kPa. And so with the combination of increase in supply pressure and careful valve selection, the static pressure loss to the site was negligible. If anything, water flows were improved.

The water industry and South East Water in particular have led the way in backflow prevention and recognized that backflow prevention plays an important role in protecting the potable water supply. Containment backflow prevention at the outlet of water meters is one small but important part of the South East Water HACCP system. This system “Hazard Analysis and Critical Control Point” is a standard developed for the food industry but adopted by South East Water for the supply of potable water.

Cross connection control and water mains of the future

Most water utilities in Australia have developed and implemented backflow prevention policies to reduce the likelihood of cross connections and backflow to the mains water supply. However, “a lot more water will pass under the bridge” before there is full and uniform acceptance and understanding of backflow prevention.

Some water utilities have only implemented backflow prevention policy for medium to high-risk industrial and commercial properties. There are other risks such as:-

1. Fire services that are unmetered and unmonitored, and have defective check valves.
2. Private water main extensions.
3. Low-level fireplugs.
4. Hydrants and hydrant standpipes.
5. Filling stations and water cart vehicles

In addition, the national drive for greater water efficiency through offering incentives, tightening regulations and increasing cost is creating more non-potable water sources and potential cross connections with rainwater tanks, greywater and greywater systems and recycled water schemes.

Water utilities with backflow prevention policies that address all actual and potential cross-connections in concert with a retrofit plan are moving to a “closed” water reticulation system. This is a system where there is a reduced likelihood and entry points for potential contaminants and pathogens; and all connections are “controlled”.

A good backflow prevention program

The relevant Australian Standards are:

AS/NZS 3500.1 Part 1, Water Services, This is an installation standard for plumbers

AS.2845.1, 2 and 3, Water supply – Backflow prevention devices, These are standards for materials, design and performance requirements of backflow devices, Air gaps and break tanks, and Field testing and maintenance

Generally, registered or licensed plumbers are required to complete a course in backflow prevention to become accredited to test and maintain backflow devices.

Water utilities can apply the above standards and plumbing qualification in implementing the backflow prevention program, however there are issues to be considered in the structure of a good program and information to the customer.

1. The customer must understand that the water will need to be shut down annually to clean the line strainer and test the backflow device. There have been problems with properties having critical water supplies but only one backflow device. Eg- manufacturing operations using water for product or cooling; pressure operated valves. The customer may need two backflow devices installed in parallel to ensure no disruption to their internal processes and equipment.
2. A plumber without the testing accreditation can install the device, but only an accredited plumber can inspect and test the installation. AS/NZS 3500.1 states that, “Testable backflow prevention devices shall be commissioned and tested after installation and prior to service”. The customer should be informed that the device should be tested after installation, before the water supply is turned on.
3. The device is required to be commissioned and tested by an accredited plumber, and thereafter tested annually. There may be some reluctance to fail the first test if the customer might choose to engage another plumber that will pass the first and subsequent tests. A solution is to audit some passed test reports and all failed test reports.
4. The purposes of water use and connections at properties are constantly changing. Random audit surveys of low to medium risk property connections may reveal elevated risk and the need to install high hazard containment backflow prevention.

A good backflow prevention program identifies all actual and potential cross-connections, has set policy for new connections and a timetable for assessment and retrofit of existing connections. Also important, are a competitive market for installation and testing, and an audit system for verification of compliance.

Peter Wenning is director of Wenning Technical Services. As a Plumbing Inspector with Melbourne Water 15 years ago, he attended several incidents of backflow and contamination of the potable water supply. He later gained experience in water meter management. Now a Hydraulic Services Consultant he has experience in designing backflow prevention for industrial and commercial properties, cross connection surveys, and implementation of backflow prevention programs at South East Water and Yarra Valley Water.
Email Peter at pwenning@bigpond.com

Thanks to Plumbing Connection Magazine for their kind permission to reproduce the above article