Cross Connection Frequently Asked Questions

1.  What is cross connection control and backflow prevention all about?

A “cross-connection” as defined by the Environmental Protection Agency, is “any actual or potential connection between the public water supply and a source of contamination or pollution”.  Such cross-connections constitute a hazard to the building occupants and can jeopardize the cleanliness and potability of the public water system, in the event of a backflow or backsiphonage event.  A cross connection control program is an organized, legally implemented and structured program to eliminate and contain the hazards to municipal potable water supply.  These programs have been implemented and are typically passed by state or local law, and enforced by the local water supplier.  In Cambridge, the designated enforcement agency is the Cambridge Water Department and a program has existed since the late 1980s.

2.  What is Backsiphonage?

A backsiphonage condition can occur whenever there is a lowered pressure between the potable and non-potable supply piping.  For instance, during the demands imposed by fire fighting operation, or in the event of a water main break, the City water pressure may suddenly drop to a pressure that is lower than that of the non-potable system.  This results in a partial vacuum being drawn on the non-potable system, and siphons the pollutants or contaminants into the potable water system.

3.  What is Backpressure?

A backpressure condition occurs whenever an elevated pressure exists between the potable and non-potable source.  These pressures can be imposed by the installation of pumps, which increase pressures above the City water supply pressure, thereby forcing non-potable water in the opposite direction of normal flow into the potable water line.  Boilers or other equipment, which heat water causing thermal expansion and resulting in pressures in excess of the incoming water pressure, also can force non-potable water into the potable water piping system.

4.  What is the Water Department's Responsibility?

As designated by the MA Department of Environmental Protection (see Regulation 310 CMR 22.22), the Cambridge Water Department is responsible for "the quality of water delivered to our consumers to the last free flowing outlet" and for the safety of the public water system in the City. To carry out our responsibility, we have State-licensed staff inspect and test all relevant backflow prevention devices throughout the City. These include double check valve assembly devices (DCVA -used primarily for fire protection systems), and reduced pressure zone (RPZ) devices.  When encountering improperly installed, maintained, or missing devices, we issue violations to the responsible party requiring that deficiencies be corrected.  We also review and approve design data sheets for the proposed new installations of backflow devices, and, after installation, we conduct the initial inspection and testing of said devices.

5.  What is my responsibility as a building owner or property manager?

The owner of any cross connection protection device shall apply for and comply with all necessary approvals and permits from the Water Department and the Inspectional Services Department; have suitable arrangements made for inspection of the facility and testing devices (including provide support staff and paying the appropriate fees); maintain a spare parts kit; and overhaul, repair or replace within 14 days (by a licensed plumber or sprinkler fitter) of the initial inspection date any device which fails a test or is found defective.   If continuous water service is necessary, two approved backflow devices shall be installed in a parallel installation. 

If you plan to remove a device, you must first obtain approval from the Water Department.

6.  Do I have adequate backflow prevention?  How can I find out?

If you have received a permit from the Water Department for backflow prevention device installation and the system was installed as permitted, you generally should have adequate protection.  However, if there is a change in use in your facility, then it is possible that the water supply may not be adequately protected.  You can arrange to have your facility inspected by a member of the Cross Connection Control group within the Engineering Division.  Please contact Tony Ippolito at 617-349-4778. 

7.  Who is legally qualified to install devices and perform maintenance on them?

Backflow preventers fall under the definition of a "plumbing appurtenance" as defined and addressed by the State Plumbing Code.  As such, these devices can legally be installed, disassembled, maintained and repaired only by a State licensed plumber or licensed sprinkler fitter.

8.  How often must a test be performed?  What is the cost?

Testing of RPZ devices occurs twice annually (generally 6 months apart), while testing of DCVA devices is once per year.  The fee for testing either type of device is $85.00 per test.