Safety & Quality

Reliability and quality go hand-in-hand when it comes to your water. CPWS is committed to providing safe, quality drinking water to its customers located in the City of Columbia and other parts of Maury County.


Clean, safe drinking water. It is something we take for granted, but every home may have potential hazards that threaten to contaminate our drinking water. Ensuring that water is safe is everyone’s responsibility.

Cross Connections – A Potential Health Hazard

The Problem

Cross Connections – What is a cross connection?  A cross connection is a direct link between a household water line and a contaminated source such as a garden hose, toilet tank, or laundry tub. The most common contaminants, such as pesticides, sewage, and detergents, can enter your drinking water system through cross connections in home water lines.

Back Siphonage – Most household cross connections are created by hoses.  Under certain conditions, the flow in household water lines can reverse and siphon contaminants into the water supply. For example, using a garden hose to spray pesticides is normally harmless, but if the city’s water supply is interrupted while you are spraying, you may have a problem. If water main pressure is reduced due to a water main break or nearby firefighting, a back siphonage effect is created.  This can draw water from your garden hose into your home water supply.  So if you have a pesticide or fertilizer sprayer attached to your garden hose, the chemicals can contaminate your water supply.

Back Pressure – Your drinking water can also be contaminated by an effect called back pressure.  Back pressure results when your water supply is connected to a system under high pressure such as a hot water boiler for home heating or a portable automobile pressure washer.  Since the pressure in these devices is higher than your home water supply, water can sometimes be forced backwards.  Contaminants in these systems, such as cleaners or soaps in a pressure washer, can then enter and contaminate your drinking water supply. For more information on cross-connection and backflow prevention, please call (931) 388-4833 ext. 7661.

The Solutions

You can easily prevent back siphonage by installing inexpensive safety devices or taking a few simple precautions.

Solution #1 Anti-Siphon Ballcocks – For example, toilet tanks contain a ballcock device which allows water into the tank after flushing. Older-style ballcocks do not have an anti-siphon feature and can allow water from the toilet tank to backflow into your drinking water line. A simple anti-siphon ballcock installed with a 25mm (1″) air gap above the overflow tube will prevent contaminated tank water from entering your water supply.

Solution #2 Hose Connection Vacuum Breakers – You can also prevent back siphonage by using an inexpensive, easy-to-install hose connection vacuum breaker.  This 1-way valve allows water to flow from the tap, but not back in.  (Drainable vacuum breakers should be installed on taps which could freeze.)

Solution #3 Air Gaps – Leave a gap of at least 1 inch or 2 times the pipe diameter (whichever is greater) between the end of a hose and a source of contamination.  This eliminates a link between the two.  Never leave a hose where it can suck contaminants back into the drinking water supply, such as in a swimming pool, bathtub, sink, or fish tank.

When to Call the Experts

Hot water boilers for heating homes, underground lawn sprinkler systems, and automobile pressure washers form cross connections which need proper control.  Due to the complexity of these systems, a qualified plumber who is a certified Cross Connection Control Specialist should be called for advice and assistance.

Safe Drinking Water is Everyone’s Responsibility

Federal and provincial governments are responsible for setting high standards for water quality. Columbia Water System is responsible for producing and supplying drinking water which meets or exceeds these standards. Homeowners are responsible for ensuring that drinking water does not become contaminated as a result of cross connection.   Remember, you are not only protecting your own water supply, but your neighbors’ as well.


CPWS works around the clock to provide top-quality water to every customer’s home and business.  Over a growing number of years, CPWS has been dedicated to producing drinking water that meets all state and federal standards.  We continually strive to adopt new methods for delivering the best-quality drinking water.  As new challenges to drinking water safety emerge, we remain vigilant in meeting the goals of source water protection, water conservation, and community education while continuing to serve the needs of all of our water users.

Each year, CPWS produces a detailed report on the status of our water quality.  Please let us know if you have any questions or concerns with the information presented.

Annual Water Quality Report (PDF)