What Homeowners Should Know About Backflow

Many homeowners take potable water for granted, but faults in your home’s waterline can contaminate your water supply and put your health at risk. One notable example is backflow, and while many modern homes’ plumbing systems feature devices designed to prevent it, those devices can fail. It’s important to understand what’s at work here and how to recognize backflow issues so a Fox Valley plumbing company can help.

The Risks of Backflow

Plumbing systems sometimes contain cross-connections where potable and nonpotable water can come into contact. These can occur at, for example, garden hoses, toilets, fire sprinklers and washing machines. Backflow refers to when the latter flows in the wrong direction back towards the main water supply through a cross-connection. Left unchecked, backflow can expose you and others to various health hazards associated with contaminated water as fertilizers, cleaning products, human waste and more enter the water supply.

What Causes Backflow?

Water flow is directed by pressure differentials and paths of least resistance—it’s common knowledge that low water pressure results in a weak flow. Backflow typically occurs in one of two scenarios:

  • Back-siphonage is the reversal of flow in a system because of negative pressure upstream, generally caused by water being drawn out at a high rate. If this occurs where cross-connections exist, nonpotable water can flow back into the water supply. Possible causes include water main breaks, use of a fire hydrant or sudden spikes in demand.
  • Back pressure is an increase in downstream pressure that causes nonpotable water to flow back away from the end use point and into the rest of the water supply. Systems using water pumps, such as power washers and most heat transfer systems, can present a risk of back pressure occurring.

How is Backflow Prevented?

Several preventative devices exist that impede water and contaminants from flowing backwards in these events. The simplest is the air gap, a space between an outlet and the fixture’s flood level like a sink faucet—these are commonly used in installing dishwashers to prevent backflow from the sink. Mechanical devices often use a combination of check valves that close when the differential pressure drops to where backflow is possible—these include atmospheric vacuum breakers, which rely on atmospheric pressure, and reduced pressure zone devices (RPZDs) that include a pressure-controlled chamber as a buffer.

While plumbing codes, including in Illinois, often mandate backflow prevention measures in residential plumbing, older homes may not already have one installed or an existing device could fail. If you suspect there are backflow issues in your system, hire a certified plumber for an inspection.