What is Cross-Connection and Backflow?

Why does this matter to me?

A cross connection is a point in a plumbing system where the potable (drinking) water supply is connected to a non-potable source. Pollutants or contaminants can enter the drinking water system through uncontrolled cross connections when back flow occurs. Cross connections are found in all plumbing systems It is important that each cross connection be identified and evaluated as to the type of back flow protection required to protect the drinking water.

Some cross connections include: 

  • wash basins and sinks
  • hose bibs
  • irrigation sprinkler systems
  • swimming pools
  • reuse water lines

A backflow is just what it sounds like: the water is flowing in the opposite direction from its normal flow. With the direction of the flow reversed, due to a change in pressures, backflow can allow contaminants to enter our drinking water system through cross connections. There are two types of backflow: backsiphonage and backpressure. Backsiphonage is caused by a negative pressure in the supply line to a facility or plumbing fixture. A few ways backsiphonage may occur are during waterline breaks, when repairs are made to the waterlines, and when shutting off the water supply. Backpressure can occur when the potable water supply is connected to another system operated at a higher pressure or has the ability to create pressure, etc. Principal causes are booster pumps, pressure vessels, and elevated plumbing. Of particular concern are homes on our system that also have private wells, customers with reuse water hook-ups, or yard irrigation systems where backflow or backsiphonage can occur. Interconnection through plumbing errors is sometimes found to be a cause of cross-contamination.

Why Should I be Concerned?

Backflow can cause contaminants to enter our drinking water system. The Florida Department of Environmental Protection categorizes possible contamination hazards as either high or low:

High - any substance that, if introduced to the public water system, could cause illness, death, or spread diseases. Examples include industrial fluids or waste. 

Low - any substance that, if introduced to the public water system, would not be a health hazard but would constitute a nuisance or be aesthetically objectionable. Examples include pollutants which would affect the color or odor of the water. 

What Can I do to Prevent Contamination?

  • Keep the ends of hose clear of all possible contaminants.
  • Buy and install hose bib type vacuum breakers on all threaded faucets in and around your home (if not already equipped with a built-in vacuum breaker.
  • Install an approved back flow prevention assembly on all undergroun dlawn irrigation systems. 
  • Don't leave hoses on the ground, or submerge them in buckets, pools, tubs, sinks, ponds, etc. 
  • Don't use spray attachments (like lawn fertilizers or herbicides/pesticides) without a backflow prevention device. 
  • Don't connect waste pipes from water softeners or other treatment systems to the sewer, submerged drain pipe, etc. 
  • Don't use a hose to unplug blocked toilets, sewers, etc. 
  • Don't connect reuse lines to the drinking water supply.