Why do water suppliers need to control cross-connections and protect their public water systems against backflow?
Backflow into the public water system can introduce contaminates, making the water in the system unusable or unsafe to drink. Every water supplier has a responsibility to provide water that is usable and safe to drink under all foreseeable circumstances.
Furthermore, consumers generally have absolute faith that water delivered to them through a public water system is always safe to drink. For these reasons, each water supplier must take reasonable precautions to protect its public water system against backflow.
What is a backflow and cross-connection?
Back flow means water flowing backwards into the water supply system. With the direction of flow reversed (due to changes in pressure), backflow can allow contaminants to enter the potable water system through cross-connections. Without proper backflow devices, something as useful as your garden hose has the potential to contaminate your home’s water supply and the public water system.
A potentially hazardous cross-connection occurs every time someone uses a garden hose sprayer to apply fertilizer or herbicides to their lawn. Without a backflow prevention device between your hose and the spigot, the contents of the hose and anything it is connected to can backflow into the home’s water system and contaminate your drinking water.
A cross-connection is any temporary or permanent connection between the potable (e.g., drinking) water system and another source containing non-potable water or other substances that could contaminate your drinking water if a backflow condition occurs.
An example of a temporary connection could be a garden hose attached to a sink or a spigot with the end of the hose submerged in a tub full of detergent. An example of a permanent connection could be the water supply line to the boiler of a hot water heating system.
How can a backflow occur?
Backflow can occur 2 different ways, by back-pressure or back-siphonage.
- Back-pressure is when a pump, elevated tank, boiler, etc. in a private system creates pressure that is greater than the pressure provided by the city water system. This can reverse the direction of flow, pushing contaminates into the drinking water system.
- Back-siphonage occurs when there is a sudden reduction in the water pressure in the distribution system, such as if a water main breaks or if the Fire Department uses a large amount of water to fight a fire. When this occurs water flow can be reversed. This can create a suction effect; drawing contaminates into the drinking water system.
How can backflow into the FWD water system be prevented?
FWD recognizes 3 methods of backflow prevention:
- Air Gap (a physical separation with disconnected and capped plumbing/piping)
- Double Check Detector Check Assembly (commonly used with Fire Systems)
- Reduced Pressure Assembly
The method of backflow prevention required is based on the degree of hazard that the property and the various uses within the property represent to the district water supply.
What is a backflow prevention assembly?
A backflow prevention assembly is an approved, testable assembly which uses spring loaded valves to prevent potential contaminates from backflowing into the city water system.
How can I prevent a cross-connection?
There are a couple of easy ways you can prevent a cross-connection:
Never place the end of a hose where it can suck contaminates into your home’s water system. For example, do not leave the end of the hose submerged in the swimming pool or a tank when filling. Always maintain at least a 1-inch gap between the end of the hose and the pool, tank or other source of potential contamination.
Use proper backflow protection devices. Each spigot at your home should have a hose-bib vacuum breaker installed. This is a simple and inexpensive device that can be purchased at any hardware store and screwed directly onto each spigot (as easy as attaching your garden hose).
How do I prevent a cross-connection with my recycled water or rainwater irrigation system?
Recycled water and rainwater should not be placed in storage containers that are connected to piped landscape irrigation systems or to a drinking water supply. Recycled water and rainwater storage containers may only be connected by hose to separate irrigation systems (i.e., hoses connected to above ground drip irrigation systems or sprinklers that are disconnected from potable water supply). Additionally, all equipment (hoses, etc.) and storage containers that come into contact with recycled water or rainwater should be dedicated for use only with non-potable water.
For instances where different systems (potable, rainwater, or recycled water) could come into contact with each other, these must be inspected by the District or County and verified to have an air-gap separation to prevent cross-connection to the drinking water supply.