What is Backflow?
Backflow can be described as "a reversal of the normal direction of flow within a piping system or as "the flow of water or other liquids, mixtures or substances into the distribution pipes of a potable water supply from any source other than the intended source of the potable water supply.
The potential for a backflow condition occurring in a water system is all too likely in many of our homes, factories and public buildings. The existence of improper plumbing connections presents cross-connections that may, under backflow conditions, permit the water to flow the wrong way within the piping.
The probability of backflow taking place at any given outlet may actually be very small. But in view of the large number of service connections, the multiple cross-connections at each service connection and the potential for cross-connections to be created, then the probability becomes very significant and must be dealt with in a positive manner.

What is Cross-Connection?

A cross-connection can be described as “any arrangement whereby backflow can occur”, or as “any arrangement of pipes, fittings, fixtures, or devices that connects a non-potable water system to a potable water system”. It is the point at which a water-using fixture is connected to the water user's potable water system.

An unprotected cross-connection provides the path or route through which backflow can occur.

It can be:

  • Permanent or temporary
  • Actual or potential
  • Direct (subject to backpressure & backsiphonage) such as a boiler or indirect (subject to backsiphonage only) such as a toilet tank fill valve


Some of the more common examples are:

  • boiler make-up lines
  • chiller make-up lines
  • fire protection systems
  • spray hoses
  • suction tees or aspirators  
  • urinals    
  • tanks or vats with a submerged inlet
  • X-ray & photo developing equipment
  • irrigation systems
  • commercial grade dishwashers
  • hand-held lawn sprayers
  • pressure washers
  • commercial grade garbage disposals or grinders
  • soap, sanitizer or wax eduction systems
  • a janitor's sink with a hose attached
  • hose bibs with a hose attached
  • toilet tanks