FAQs • Dayton, OH • CivicEngage

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 pounds of pressure coinciding with a reduction of the city water supply below this 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.

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Backflow Prevention

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 pounds of pressure coinciding with a reduction of the city water supply below this 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 allowing the potable water supply to be connected to a line that contains a contaminant. An example is the common garden hose attached to a sill cock and the end of the hose is lying in 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?: To view the ways to prevent backflow for residential and commercial and industrial properties, please view the
Prevent Backflow Conditions page.