Avoid Cross Connections Using Air Gaps

by Frank G. Ross
 

We all know how important water is to life.  Here in America we take a clean water supply for granted.  However, we all have a certain responsibility to maintain this level of quality.  Incorrect plumbing installations can compromise the water supply and result in real health hazards. One little known health-related plumbing concept of which everyone should be aware is cross connections.

According to the Utah Chapter American Backflow Prevention Association (ABPA) website “a cross-connection is an unprotected actual or potential connection between a potable water system used to supply water for drinking purposes and any source or system containing unapproved water or a substance that is not or cannot be approved as safe, wholesome, and potable.”  In many cases the non-potable source can contain harmful toxins or bacteria.

Cross connections become problematic when conditions create backflow. Backflow occurs when the flow of water in the system is reversed due to a drop in pressure. “Water distribution systems are designed with the intention of the water flowing in a certain direction-- from the distribution system to the consumer,” states the ABPA website. “However, hydraulic conditions within the system may deviate from the "normal" conditions, causing water to flow in the opposite direction. Therefore, it is possible (and common) for the water to flow in the opposite direction in unprotected systems.”  A drop in pressure may be caused by breakages in water mains or nearby firefighting.

Any time there is a possibility for the supply water to come in contact with drain water or any other non-potable water, a cross connection exists.  Potential cross connections around the home include hoses lying in puddles, faucets below the flood rim of a sink or tub, underground sprinkler system piping, handheld shower heads lying in tubs, and pesticide nozzles that attach to the end of a hose.

Generally appliances and fixtures are designed to eliminate the potential for cross connection when properly installed.  For example, sink and tub faucets should be installed so that a gap exists between the end of the faucet and the flood rim of the tub or sink.  This gap makes it practically impossible for the water in the sink or tub to flow into the faucet.

In some cases, however, it is up to the installer to understand and take proper precautions to avoid cross connections. During the process of home inspection, I most commonly encounter cross connections at water softener installations.  The minimum required air gap is one inch. All too often this requirement has been overlooked.  In the unlikely event of a sewer line backup, sewage may be forced backwards up the drain and into the water softener corrupting the water supply. There is also the possibility for bacterial growth to follow a path up such drains causing contamination even without a backflow incident.

Homeowners can take precautions to avoid cross contamination such as:

• 1. Never leave the end of a hose where contaminants can be drawn back into the drinking water.

• 2. Never leave handheld shower nozzles lying in the bottom of the shower or tub.

• 3. If you have a short hose attached to the faucet of a utility sink, do not leave the hose lying in the bottom of the sink.

For more information (and links to even more information) on this topic visit www.nobackflow.com.

Frank Ross is a Certified Utah Home Inspector for Pillar to Post Professional Home Inspection a full member of the National Association of Certified Home Inspectors and a member in good standing with the Utah Better Business Bureau.  Readers may contact Mr. Ross at (435) 867-6400 or frank.ross@pillartopost.com