Backflow & Cross Connection


Protecting the Water Supply after Delivery

Harwich Water Department works very hard to protect the quality of water delivered to our customers, from the time the water pumped from the aquifer using deeply set gravel-packed wells, to the when it reaches our customers.  Is there still a need to protect the water after it is delivered? The answer is “yes”!

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 utilizing equipment, 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.

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:

Contamination as a Result of Cross Contamination

Serious illness, even deaths, 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:

Condominium Complex – Water treated with hexavalent chromium from a cooling tower backflowed into the drinking water system through an unprotected water line.  More than 600 residents relied on bottled water for three days.

High School – Chromates were pumped into the drinking water system from a boiler.  Fortunately, the custodian noted yellow-colored water in a drinking fountain.  The school was closed for five days to flush and chlorinate water lines and install a backflow preventer.

College Athletic Field – Eight-three football team members and coaching staff were diagnosed with infectious hepatitis after drinking water from a fountain on the field.  Water backflowed from the irrigation system in to the water line when a local fire reduced water pressure.

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 facility or the surrounding neighborhood is not contaminated. 

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:


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:


The Massachusetts Plumbing Code (248 CMR 2.14) and Massachusetts Drinking Water Regulations (310 CMR 22.22) both require installation of backflow preventers at all cross connections.  In addition, backflow preventers at cross connections are to be inspected once a year by a certified backflow preventer inspector.  Local water suppliers are also required by the Department of Environmental Protection (DEP) to inspect cross connections twice a year.  Please contact the Harwich Water Department at 508-432-0304 if you have a device that needs inspected.