Reduced pressure backflow prevention device

Double check valve device

Pressure Vacuum Breaker

Spill proof Pressure Vacuum Breaker

Air Gap

Boundary

Zone

Individual protection

Any supply downstream of a backflow prevention device should be classed as non potable, unless proven otherwise

Designers, Plumbers, Engineers, who is responsible?

What needs to be considered before installing a backflow device,

How will the installation effect the testing and maintenance of the device?

Will there still be enough water to all receiving vessels?

(fixture, fittings, appliances, plant equipment)

Degree of hazard

Where to get that information? ◦ TA inspectors?

This gives the following estimate of risk

Likelihood Consequences

Insignificant Minor Moderate Major Catastrophic

Almost certain High High Extreme Extreme Extreme

Likely Moderate High High Extreme Extreme

Possible Low Moderate High Extreme Extreme

Unlikely Low Low Moderate High Extreme

Rare Low Low Moderate High High

AS/NZ3500.1:2003 section 4 does not apply to NZ as an acceptable solution.

This Section applies to Australia only.

a) AS/NZS 3500.1 Section 2, Section 3 and Appendix C (note that Appendix C is part of this Verification Method even though it is included in the standard as an “Informative” Appendix c, Sizing method for supplying piping for dwellings

In New Zealand, reference may be made to the New Zealand Building Code Document G12/VM1, Water Supplies, for alternative information on cross-connection control and backflow prevention. Examples of potential cross connections are given in Appendix E.

Any condition, device or practice which, in

connection with the potable water supply system, would constitute a nuisance, by colour, odour or taste, but not injure or endanger health.

Dual check valve

Double check valve

Air gap

Hose connection vacuum breaker ?

Any condition, device or practice which, in connection with the potable water supply system, has the potential to injure or endanger health.

Double check valve

Reduce Pressure zone device RPZD

Air Gap

Pressure vacuum breakers

High hazard Any condition, device or practice which, in connection with the potable water supply system, has the potential to cause death.

Reduce pressure zone device RPZD

Spill proof pressure vacuum breaker

Pressure vacuum breaker

Air gap

Vacuum breaker

When looking at a property you need to consider the water system

from the point of supply to the last flowing tap.

Any water supply downstream of a backflow prevention device should be considered non potable, until you prove otherwise.

When limitations are placed on you on where the installation of a backflow device can go, the type of backflow device you need to install, will give an insight as to what type of backflow device you can use

Sticking it in the ceiling is not the answer

RPZD Installation

2 check valves with an automatic relief valve in between both checks.

Hazard Rating: High, medium and low.

Can be installed on both backpressure & backsiphonage conditions.

Typical manufacturers installation requirements for RPZD

For indoor installations, it is important that the assembly be easily accessible to facilitate testing and servicing.

If it is located in a line close to a wall, be sure the test cocks are easily accessible.

A drain line and air gap should be piped from the relief valve connection as shown where evidence of discharge will be clearly visible and so that water damage will not occur.

A. The RPZ device should always be installed in an accessible location to facilitate testing and servicing Check the local codes to ensure that the backflow preventer is installed in compliance, such as the proper height above the ground.

(G12 AS1 and AS/NZ3500 300mm and above flood level)

B. We recommend a strainer be installed ahead of RPZ device assemblies to protect the internal components from unnecessary fouling.

Do not install with strainer when backflow preventer is used on seldom-used water lines which are called upon only during emergencies, such as fire sprinkler lines.

Start Up: The downstream shutoff should be closed. Open upstream slowly and fill valve. When valve is filled, open the downstream shutoff slowly and fill the water supply system. This is necessary to avoid water hammer or shock damage.

C. Water discharge from the relief valve should be vented in accordance with code requirements. The relief valve should never be solidly piped into a drainage ditch, sewer or sump. The discharge should be terminated approximately 12" above the ground or through an air gap piped to a floor drain.

Relief Valve Discharge Rates The installation of an air gap with the drain line terminating above a floor drain will handle any normal discharge or nuisance spitting through the relief valve. However, floor drain size may need to be designed to prevent water damage caused by a catastrophic failure condition. Please refer manufacturers instructions for maximum relief valve discharge rates, size and capacity of typical floor drains.

..\..\Backflow prevention videos\Failing RPZ Backflow Preventers.mp4

This gives the following estimate of potential risk

Likelihood Consequences

Insignificant Minor Moderate Major Catastrophic

Almost certain High High Extreme Extreme Extreme

Likely Moderate High High Extreme Extreme

Possible Low Moderate High Extreme Extreme

Unlikely Low Low Moderate High Extreme

Rare Low Low Moderate High High

Reference to manufacturers instructions as an example for maximum relief valve discharge rates, size and capacity of typical floor drains.

2" (50 mm) 208 lpm 5" (125 mm) 1325 lpm

3" (80 mm) 424 lpm 6" (150 mm) 1703 lpm

4" (100 mm) 643 lpm 8" (200 mm) 2877 lpm

Drain line length, number of changes in direction, and fall, will all have an effect on the discharge from drain lines

Reference to manufacturers instructions as an example for maximum relief valve discharge rates, size and capacity of typical floor drains.

NOTE: Manufacturers have different discharge rates.

20mm device with 50 psi will discharge

approx 30 gpm = 113.70lpm same

Change that to 70psi = 482kpa the

device will discharge 38 gpm =144lpm

189 lpm

80mm device with 50 psi will discharge

200 gpm = 750lpm 1137 lpm

Change that to 70 psi = 482 kpa the

device will discharge

225 lpm = 852.75 lpm 1326.50 lpm

DCV installation

2 check valves.

Hazard Rating: Medium and low.

Can be installed on both backsiphonage & backpressure conditions.

Resilient seated isolating valves either side of the device

A line strainer must be installed upstream.

Install valve inline with arrow on valve body pointing in the direction of flow.

For indoor installations, it is important that the valve be easily accessible to facilitate testing and servicing.

Do not install in a concealed location.

End?