Cross-Connection Control: The Basics Every Small System Operator Needs

A cross-connection is any actual or potential link between the public water supply and a source of contamination. The contamination doesn't have to be reaching anyone right now for the risk to be real: the connection just has to exist for conditions that allow backflow to make it a problem.

For most small public water systems, cross-connection control gets less attention than it deserves. The issues tend to be invisible until something goes wrong.

How Backflow Happens

Water in a distribution system flows in the intended direction as long as system pressure is greater than the pressure at the service connection. Two conditions break that assumption.

Back-pressure occurs when pressure on the customer's side exceeds system pressure: this can happen with booster pumps, elevated tanks, or thermal expansion. Back-siphonage occurs when system pressure drops below atmospheric pressure, typically during a main break, high demand, or firefighting operations nearby. Either condition can draw contaminated water from a connected source back into the distribution system.

Common Cross-Connections in Small Systems

The most common cross-connections found during surveys of small public water systems:

• Garden hose connections: a hose submerged in a bucket, pond, or sprayer creates a direct cross-connection. Hose bib vacuum breakers are the fix and they're inexpensive.
• Irrigation systems: any in-ground irrigation system without an approved backflow preventer is a cross-connection.
• Boiler systems: commercial and industrial customers with chemical treatment in their boiler water are a high-hazard cross-connection risk.
• Chemical storage and mixing operations: any facility that mixes chemicals using a water connection.
• Medical and dental facilities: equipment that connects to the water supply and uses it in proximity to potential contaminants.

Your Cross-Connection Control Program

EPA and most state primacy agencies require community water systems to have a cross-connection control program. At minimum this includes identifying high-hazard service connections, requiring installation of approved backflow prevention assemblies at those connections, and maintaining a testing schedule for those devices.

Reduced pressure zone (RPZ) assemblies are the standard requirement for high-hazard connections. Double check valves are acceptable for lower-hazard connections in many states. Atmospheric vacuum breakers work for non-continuous pressure applications.

All mechanical backflow prevention devices require annual testing by a certified tester. Keep your test records. This is a sanitary survey item and a common finding when records are incomplete.

Customer Communication

Your customers generally don't know what a cross-connection is or that they might have one. Including a cross-connection awareness item in your CCR or a periodic customer newsletter reduces your risk and builds credibility as an operator who takes public health seriously.