Eliminating Cross-Flow Contamination

2 min read

What is cross-flow contamination? 

“Cross-flow” is a term used to describe two liquid circuits that become connected by liquid from one circuit flowing across to another circuit. Hence the term “cross-flow”. 

Is cross-flow contamination dangerous? 

Cross-flow should be avoided because it’s illegal and harmful to contaminate town/main water supplies. 

How to Avoid Cross-Flow Contamination 

There are many devices available to ensure cross flow is avoided. These include: 

• Double Check Valves 
• Reduced Pressure Zone Valve (RPZ)
• Air Gap (Break Tanks)
• Automatic Refill Units or Pressurisation Systems 

When is cross-flow contamination likely to occur? 

Cross-flow will occur if there is a pressure imbalance between two separate circuits. If liquid crosses over into the separate circuit, it will transfer pollutants from one to the other. 

For example, a laboratory where water is being fed from the town water supply is using that water for laboratory functions. If this water becomes contaminated by another system in the laboratory, it could backflow into the original circuit and fully contaminate the town’s water supply. 

Further to this, imagine if the pressure in the laboratory circuit was higher than the mains water circuit. Because of this difference in pressure, the liquid would flow back and contaminate the municipal water system. 

Where is cross-flow contamination most-likely to occur? 

By their very nature, closed-loop systems are an area where cross-flow contamination can occur. Such places where closed-loop systems are used include pharmaceutical laboratories, mortuaries, and HAZMAT sites. 

Cross-Contamination Codes and Standards 

Local Authorities protect their populations by issuing rules and codes to ensure installation and plumbing practices are to a high standard. 

In Australia, the standard that specifies requirements for the design, installation, and commissioning of water services from a point of connection to the points of discharge is AS3500.1:2021. This standard applies to all installations and alterations, both new and existing. 

The Masterflow Solution 

Masterflow has designed pressurisation units specifically for use in closed-loop systems. 
The units provide backflow prevention and automatic makeup in accordance with AS3500. 

Conversely, the system also provides refilling when there are minor losses in the system. In the event of major system leaks, the make-up water is regulated, limiting the potential water damage.  

The highlight of this system and what makes it ideal for high contamination risk sites is the physical air gap of the break tank. The air gap works to eliminate the possibility of backflow to the water supply system. The systems come complete with a pump, break tank, expansion tank, pressure switch, regulator valves and a wall-mounted cabinet.  

The system is self-sufficient and does not require the statutory maintenance checks that other pressurisation systems require. 

Are you curious as to whether your project might involve a potentially dangerous cross-flow situation? 

Contact us here.