Backflow Prevention

Cross Connection Control & Backflow Prevention Explanation

The Cross Connection and Backflow Prevention Program of the Norridgewock Water District is designed to regulate, control, and prevent the contamination of your drinking water by the backflow of water or other liquids, mixtures or substances into the distribution pipes of the Norridgewock water supply system from a source or sources other than its intended source.

It is the responsibility of a public water system to provide water which is safe to consume.  Since active, unprotected, or inadequately protected cross-connections provide a real and present threat to the safety of the water being consumed, we have developed the following program to protect your drinking water.


Backflow means the reversal of water flow from its normal or intended direction of flow.  It is possible for the flow to be reversed, known as back-siphonage, and flow from the customer’s plumbing system back into the public water distribution system.  If cross-connections exist within the user’s plumbing system when backflow occurs, then it is possible to contaminate the public water system.

A cross-connection occurs when a drinking water supply pipe connects to a non-drinking water supply source or pipe.  An example of this is a connection with a residential home.  For example, if you have a hose that has a submerged end in a kiddie pool or a carwash bucket, this is a cross-connection.

Back-siphonage may occur when the water pressure within the distribution system falls below that of the plumbing system it is supplying.  The loss of pressure can be caused by a broken water main, or a fire nearby where the fire department is using large quantities of water.  Any building near the break or the fire hydrant being used will experience a lowering of the water pressure.

Where backflow occurs and cross-connections are present you have all the necessary elements for contamination of the plumbing system and, subsequently, contamination of the public water system.

As an example:  Suppose an automatic lawn sprinkler system is spraying a lawn when all of a sudden a back-siphonage occurs due to a fire truck pumping water or water rushing from a broken main.  The resulting backflow from the lawn sprinkler system will flow into the plumbing system and then into the water distribution system.  As the water backflows it can suck contaminants into the lines through the sprinkler heads (insects, pesticides, herbicides, fungicides, fertilizers, worms, etc).  Once in the distribution lines, the contamination could go anywhere in the public water system.

To prevent backflow from non-potable sources into our public water system, check valves or backflow prevention devices installed at the site of the cross-connection can protect the plumbing system from contamination.  Placed just downstream of a water meter to an establishment, they can protect the public water system from any contamination that may occur within the entire establishment’s plumbing system.

Cross Connection-Backflow Prevention Program


State Cross-Connection Rules