If water is under pressure how can I have backflow?
The water supply in our homes is normally under pressure, but occasions can arise when the pressure drops. For example, if there is a fire in your neighborhood and the fire department begins to pump large amounts of water; the water pressure in the surrounding area can drop.

This low pressure or no pressure can contribute to conditions that allow water to flow backwards. If at the same time, a fixture in the house is open and submerged in water, water can be siphoned back into the water supply. Or if at the same time as the fire in the neighborhood, you were using a garden hose with a sprayer jar attached to the end of the hose filled with fertilizer, that fertilizer (or whatever was in the jar) could be sucked back into the household water supply.

The next time water was drawn from a fixture inside the house that fertilizer would be in the water. This is the reason that modern plumbing codes require anti-siphon protection to be installed on the water lines that lead to garden hose connections.

Show All Answers

1. If water is under pressure how can I have backflow?
2. My outside faucets are new and have vacuum breakers built in, are there other things I need to be concerned about in back flow protection?
3. What is cross connection?
4. Why is the City doing this program now?
5. Is this an ongoing program?