What is Backflow?September 16, 2016
How to prevent Backflow ContaminationSeptember 16, 2016
Backflow Device Installation
Backflow is the undesirable reversal of the flow of water and other undesirable substances from any source including used water, industrial fluids, and/or gases into the distribution pipes of potable water system.
It could be in the form of backpressure or back siphonage.
There are several types of mechanical backflow prevention devices used in Australia. Some of the more common ones include Reduced Pressure Principle Backflow Preventer, Double Check Valve Assembly, Pressure Vacuum Breaker and Atmospheric Vacuum Breaker.
While installing a backflow preventer, there are many details that should be evaluated before beginning the actual work. Two basic considerations that should be evaluated in the installation process are the hydraulic conditions and the mechanical conditions.
The hydraulic conditions concern the flow of water through the piping system. The mechanical conditions involve the pipe, valves and fittings required to properly install the backflow preventer into a piping system.
To ensure an effective installation, the concerned personnel must also know the rules to comply with for the installation of such devices.
A backflow prevention assembly may be installed as a service protection assembly or an internal protection assembly. A service protection assembly is installed at the point of service to a water user and it is installed to protect the distribution system from a backflow event.
Selection of right kind of device is also important for plumbing systems. The installation depends on the kind of device.
Here are some of the things that should be taken care of while installing back flow preventers:
- For Reduced Pressure Devices:
Principle Backflow Preventers can be used with service connection and also for internal protection. There should be a minimum clearance of 12 inches above the floor or grade. This is to ensure an air gap beneath the relief valve and any water that could puddle beneath the device.
The maximum height must be chosen in a way that it is feasible to test and maintain the device as and when necessary. Likewise, if the device is in a protective enclosure or is mounted against a wall, the minimum distance must permit testing and maintenance of the device.
Once the devices are installed in conformity with the state laws, it is also important to test them before use. The devices should also be tested periodically during maintenance.
- For Double Check Valve Assembly:
A Double Check Valve Assembly can also be used with service connections for internal protection. The minimum and the maximum distances are the same as they are for the Reduced Pressure Principle device.
- For Pressure Vacuum Breaker:
The pressure vacuum breaker cannot be installed where there is a possibility of backpressure. It should only be used where there may be back siphonage. The pressure vacuum breaker can have shut-off valves down-stream of the device. The device must be installed at least 12 inches above the highest outlet or, if it is feeding an open tank, at least 12 inches above the highest overflow rim of the tank.
- For Atmospheric Vacuum Breaker:
Like pressure vacuum breakers, the atmospheric vacuum breaker cannot be installed where there can be backpressure, only where there can be back siphonage. The atmospheric vacuum breaker cannot have any shut-off valves downstream of it. It also must be installed at least 6 inches above the highest outlet or the topmost overflow rim of a non- pressure tank.