Backflow

Twight’s Plumbing can carry out your annual backflow testing requirements.

We can also repair or replace faulty Reduced Pressure Zone Devices (RPZD) and Double Check Valve (DCV) Devices or install new.

Just call to arrange a booking or email us your notification from the Water Corporation and we will have it sorted in no time.

What Is Backflow?

Backflow is a plumbing term for an unwanted flow of water in the reverse direction. Causes: Backflow occurs for one of two reasons, either back pressure or back syphonage 

Back Pressure is the result of a higher pressure in the system than its supply 

Back Syphonage is the result of supply pressure being lowered below that of the system. This may occur when a supply is interrupted or drained down 

Ref: Wikipedia

Some common causes of this change in back pressure include; 

  • Broken water main 
  • The water outlet at the property is higher than the water main 
  • Heavy water use downstream, reduces upstream pressure 
  • Water being pumped from the mains during a fire. 

It can be a serious health risk for the contamination of potable water supplies with foul water

Backflow Risk Rating

Backflow risk can be classed as low, medium or high as per AS/NZS 3500.1:2018 

  • Low risk – any condition, device or practice in connection with the drinking water supply system that constitutes a nuisance but does not endanger health or cause injury. 
  • Medium risk – any condition, device or practice in connection with the drinking water supply system that could endanger health. 
  • High risk – any condition, device or practice in connection with the drinking water supply system that could cause death.

How Is Backflow Risk Rating Determined?

At the time of approval of a building development application the Water Corporation of WA will determine the Property Risk Rating.  

These following building application types will be assess for backflow risk. 

  • New developments 
  • Redevelopments of existing facilities 
  • Changes to any existing water service 
  • Additions and alterations (includes where no water service applications are included, applicable only if the property has existing meters) 
  • Multiple residence and/or commercial (includes where no water service applications are included, applicable only if the property has existing meters) 
  • Any applications that involve a fire service 
  • Any applications where the minimum water service size applied for is greater than 25mm in size (except fire services, where the backflow advice applies regardless of the service size). 

Please refer to Water Corporation for further details

Backflow Regulations

All the information you require can be found on the Water Corporation of WA’s Website

Who Can Install and Test A Backflow Device

Only a licensed Plumbing Contractor can install a Backflow Device. Testable Backflow Prevention Devices at the Property Boundary must be tested annually by a Licensed Plumbing Contractor qualified to test the Devices. Reach out to Twight’s Plumbing to arrange a Backflow test or installation.

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