Backflow Prevention & Cross Connection

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Protecting the Water Supply after Delivery

Harwich Water works hard to protect the quality of water delivered to our customers, from the time the water is pumped from the aquifer using deeply set gravel-packed wells, to when it reaches our customers, there still a need to protect the water after it is delivered. Water distribution systems are continuously jeopardized by cross connections and this is a major concern amongst public water suppliers and regulators.  Although regulations exist, all customers hold the responsibility for identifying cross connections and ensure that appropriate valves, known as backflow prevention devices, are installed and maintained.


When public water supplier piping connects to various plumbing fixtures or water equipment, a cross connection is created.  If improperly protected, contamination can result when a backflow even occurs; allowing contaminates to reverse flow from the fixture/equipment back into the drinking water piping and supply.

Backflow; Back-Pressure and Backsiphonage

Water of questionable quality or chemicals used in a system or equipment can end up in the drinking water line as a result of back pressure or backsiphonage.  Back-pressure occurs when the pressure in the equipment or system (A/C, boiler, etc.) is greater than the pressure in the drinking water line.  Backsiphonage occurs when the pressure in the drinking water line drops (main breaks, fires, heavy demand) and contaminants are sucked out of the system into the drinking water line.  Backflow is a problem that many water consumers are unaware of, a problem that each and every water customer has a responsibility to prevent.

Cross Connection Culprits

A cross connection is formed at any point where a drinking water line connects to any equipment or system containing chemicals or water of questionable quality.  Cross connection can occur at boilers, air conditioning systems, fire sprinkler systems, Irrigation systems, laboratory equipment, planting tanks and chemical vats to name a few.

Contamination as a Result of Cross Contamination

Serious illness, and even death, have been caused by backflow contamination incidents that could have been prevented.  Various contaminants entering drinking water distribution systems as a result of backflow have been known to cause such hazards as outbreaks of hepatitis A, gastroenteritis, legionnaire’s disease, chemical poisoning, and body lesions (from exposure through showering); and exploding plumbing fixtures.   Below are just a few other examples of Case Histories in Massachusetts:

Customer Responsibility

As an owner of one or more cross connections, it is your responsibility to maintain the system so that drinking water at your location or the surrounding neighborhood is not contaminated. If you have a backflow device on the system, have it inspected and tested every year by a certified tester to insure it is working properly.


Without the proper protection, something as simple as a garden hose has the potential to contaminate or pollute the drinking water lines in your house.  In fact, over half of the country’s cross connection incidents involve unprotected garden hoses.  These are very simple steps that you as a drinking water user can take to prevent such hazards:

It is imperative that you follow the above criteria to ensure that the drinking water in your facility and the surrounding neighborhood remains safe for consumption.

Commercial, Industrial and Institutions

If you are the owner or manager of a property that is being used as a commercial, industrial or institutional facility, you must have your plumbing system surveyed for cross connections.  If your property has not been surveyed for cross connections, contact the Harwich Water Department for scheduling.

In summary, as an owner of cross connections you bear the following responsibilities:

If you have any questions or would like additional information, please contact call the department at 508-432-0304.