1. What is Backflow?

• Backflow is the reverse flow of water caused by a loss of pressure in the system or connections to the system that have a higher pressure than the supply pressure.

2. What is back-siphonage?

• Back-siphonage is the reversal of normal flow in a system caused by a negative pressure (vacuum or partial vacuum) in the supply piping.

3. What factors can cause back-siphonage?

• Back-siphonage can be created when there is stoppage of the water supply due to nearby fire-fighting, repairs or breaks in city main, etc. The effect is similar to the sipping of an ice cream soda by inhaling through a straw, which induces a flow in the opposite direction.

4. What factors can cause a back pressure-backflow condition?

• Back pressure-backflow is created whenever the downstream pressure exceeds the supply pressure, which is possible in installations such as heating systems, elevated tanks, and pressure-producing systems. An example would be a hot water space-heating boiler operating under 15-20 lbs. pressure coincidental with a reduction of the city water supply below such pressure (or higher in most commercial boilers). As water tends to flow in the direction of least resistance, a back pressure-backflow condition would be created and the contaminated boiler water would flow into the potable water supply.

5. What is a cross connection?

• A cross connection is a direct arrangement of a piping line, which allows the potable water supply to be connected to a line, which contains a contaminant. An example is the common garden hose attached to a sill cock at the end of the hose lying is a cesspool. Other examples are a garden hose attached to a service sink with the end of the hose submerged in a tub full of detergent, supply lines connected to bottom-fed tanks, supply lines to boilers.

6. What is the most common form of a cross connection?

• Ironically, the ordinary garden hose is the most common offender as it can be easily connected to the potable water supply and used for a variety of potentially dangerous applications.

7. How can you help prevent Backflow conditions?

• Residential Properties:
  • Use anti-siphon Ball Cock assemblies in toilets.
  • Install hose BIBB Vacuum Breakers on all outside hose connections.
  • Use approved Backflow device for in ground irrigation systems.
• Commercial & Industrial Properties:
  • Use approved Backflow device to protect the cross connection.
  • Install approved Backflow device at the point of service to protect any Backflow threat from entering the public main.