What Is a Cross Connection In Plumbing?

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So, you turn on your tap to expect a glass of clean water. Rather, what you get in return is a mix of harmful chemicals and bacteria. Well, this is a cross connection in plumbing terms. These connections are often hidden in your plumbing system. They create a path for contaminants to enter the supply of your drinking water. This makes the water unsafe for you and your loved ones.

Cross Connection Video

Water is the lifeblood of any property, and is essential to human life. 🩸

It’s important that our water sources are safe and clean for human consumption.

But when there’s a lack of maintenance and proper protocols, water can easily be contaminated and deemed unsafe. 🦠

Leaving the property with expensive repairs, and unlivable conditions. 😔

One of the ways this can happen are through what’s called cross connections.

Cross connections are caused by a lack of proper protection between safe and unsafe water.

In order to provide proper protection of our water, we have to make sure we leave proper air gap between safe and unsafe water.

Types of Cross Connections

Direct Cross Connections

A physical link between the potable water system and a source of contamination is known as a direct cross connection.

Indirect Cross Connections

There is always a potential for contamination without a direct connection of its source to the drinking water. This is an indirect cross connection.

What Is a Source of Cross Connection?

Cross connections in plumbing systems arise from various factors:

Wrong Plumbing Practices

Incorrect installation and maintenance of plumbing systems can result in cross connections:

  • Plumbing pipes carrying hazardous water that is directly connected to a potable water line.
  • Garden hoses connected to a chemical sprayer.
  • Fixtures installed below the flood level rim of sinks, tubs, or tanks.
  • Temporary Hoses submerged in a pool, a bucket of soapy water, or a container of chemicals.
  • A lawn irrigation system drawing polluted water in case of backflows.
  • Boilers cause water to flow back into the potable water system due to pressure changes.
  • Accidental connections made during plumbing repairs or installations.


When water flows in the opposite direction from its intended path, backflow occurs and results in cross connections.

The two types of backflow are backpressure & backsiphonage.

The pressure in a non-drinking water system sometimes exceeds that in a portable one. This causes backpressure, which forces the impurities back into the drinking water supply.

There’s more to it!

A sudden drop of pressure in the potable water system sometimes creates a vacuum. This is backsiphonage that can also introduce pollutants into the drinking water. The reasons can be main water line breaks or high water demand. Water pumps can also fail and cause these backflows.

Note: Plumbing systems without backflow prevention devices like air gaps or check valves are more susceptible to cross connections.

Environmental Factors

Floodwater can enter the drinking water system of your home or business through cracks in the pipes or joints of your plumbing. Also, earthquakes can cause breaks or shifts in water lines and add pollutants to the portable water.

How Do I Stop Cross Connection?

Effective prevention of cross connections is essential to warrant the safety and purity of drinking water:

Install Backflow Prevention Devices

Backflow prevention devices can quickly overcome cross connections and resolve plumbing problems:

  • Air Gaps: An obstructed vertical space between the drinking water supply and the source of impurities. Commonly used in sinks, tanks, and fixtures.
  • Check Valves: Helps water to flow in a single direction. Suitable for simple plumbing where less backflow protection is needed.
  • Double Check Valve Assemblies: Two check valves for added protection.
  • Reduced Pressure Zone (RPZ) Assemblies: Give maximum protection by establishing a lower water pressure zone. Required in high-hazard environments like industrial spaces.

Inspections, Installations, and Maintenance

Regular monitoring and maintenance of your plumbing ensures cross conections won’t occur:

  • Scheduled Inspections: Check all potential cross connection points, backflow prevention devices, and plumbing fixtures.
  • Maintenance: Carry out periodic testing of backflow preventers to verify their effectiveness. Clean, repair, and replace them as needed.
  • Correct Fixture Placement: Install fixtures like faucets and hose bibs above the flood level rim.
  • Ensure Gaps: Maintain adequate separation between potable and non-potable systems.
  • Avoid Temporary Connections: Minimize the use of temporary connections. Also, confirm they are properly disconnected and do not pose a risk when not in use.
  • Compliance: Acquaint yourself with local plumbing codes and make sure all plumbing installations and repairs comply with these standards. 


Preventing cross connections is crucial for maintaining the safety and quality of drinking water. Contaminated water can bring on serious health issues, including gastrointestinal illnesses and other waterborne diseases. Regular inspections, maintenance, and the use of appropriate backflow prevention devices are essential for safeguarding your well-being.