When you’re running a business, it’s difficult to focus on anything that isn’t at the top of your priority list. That doesn’t leave much time for making sure you don’t unknowingly break one of the hundreds of laws that apply to businesses in Australia. So, if you’re unfamiliar with the Victoria Water Industry Regulations 2006 and what they say about backflow prevention, you’re not alone. Here’s what you need to know:

What is Backflow?

Put simply, backflow occurs when water in a system of pipework flows the opposite way to its correct direction – into the main reticulation system, and particularly into the drinking water supply. When the backflow is from a contaminated or polluted source, the outcome can be serious. Severe sickness is the likely outcome, with death a possibility in extreme cases.

It’s not hard to see why the law requires every business owner or manager to have a licensed plumber fit and maintain backflow-prevention devices in the drinking-water supply. This is particularly important if you have more than one water system on your premises – for irrigation or industrial processing, for example – and there is any possibility of cross-contamination between the two systems.

Backflow doesn’t affect only you and the people on your premises. If contaminated water ends up in the main potable (drinking) water supply, it can flow into any other property connected to the water main. Large numbers of people can become ill.

What Causes Backflow?

Backflow usually happens for one of two underlying reasons – either:
• the supply pressure drops because of a leak or a fault (back-siphonage); or
• the downstream pressure at your premises increases unintentionally (back pressure).

Back-siphonage and back pressure are more likely to occur when you have a second water system connected to your potable water main – known as a cross-connection. Any organisation that uses water in its day-to-day business – including hospitals, universities, laboratories, farms, market gardens and nurseries, industrial plants and commercial kitchens – may have a cross-connection, either deliberately or inadvertently.

Let’s take a look at why back-siphonage and back pressure occur.


If your supply pressure drops, the cause may not be obvious; you may not notice anything other than a slight reduction in the water flow from your taps. A leaking water main – maybe as a result of excavation damage – or a failed supply pump are typical causes.

Less often, another local user taking an excessive amount of water, particularly from a water main that isn’t big enough for the job, can also cause a significant reduction in your supply pressure.

In the absence of a backflow-prevention device, low supply pressure causes water from your premises to be drawn back into the main water pipework. If your water pipes are cross-connected to a secondary system, particularly one with a booster pump, the risk increases.

Back Pressure

Causes of back pressure are numerous. Anything that increases your water pressure, including secondary water pumps, pressure intensifiers, industrial machinery and laboratory equipment, is capable of causing back pressure.

If you’re using any of these (or anything similar) on your premises, you must not connect it directly to the water main – whether deliberately or accidentally. If you do, you will pump water back into the reticulation pipework, contaminating the supply.

Inadvertent cross-connections are one of the most common causes of back pressure. Many industrial processes reduce overall water consumption by using a mixture of mains water and recycled (or grey) water. If recycled water is pumped into the processing equipment and is not prevented from entering the mains water feed, a cross-connection exists.

A Word About Cross-Connections

Cross-connections are not always obvious. A cross-connection is “any actual or potential connection between a water-supply installation and a source of actual or potential contamination or pollution”. Note the words “or potential” – a clear indication that you should always be on the lookout for possible sources of contamination.

Some potential cross-connections are easy to eliminate. Flexible hoses left trailing instead of being stowed can end up dangling in stormwater, river water or seawater, providing an easy route for pollution to enter the water main. Storage tanks with top-fitted filler pipes that are too long end up with the mouth of the pipe below the surface when the tank is full – a classic path for back-siphoning.

Perhaps the most avoidable cause of cross-connection is the well-intentioned but incompetent bodge … don’t be tempted to tinker with your plumbing just because you can. Get a professional to assess and carry out any modification or extension to your pipework.

Where Does that Leave Me?

The Water Industry Regulations 2006 state that if you have a water service to your property, you must “cause a licensed plumber to fit the service with a backflow prevention device.” In essence, a backflow-prevention device is a one-way valve that only allows water to flow in the correct direction.
The type of device required depends on the hazard rating of the premises, which is set out in Australian Standard AS 3500.1:

  • “High” hazard rating applies when there is “any condition, device or practice within the water supply system and its operation which has the potential to cause death.”
  •  “Medium” hazard rating applies when there is “any condition, device or practice within the water supply system and its operation which could endanger health.”
  • “Low” hazard rating applies only when there is no risk to health.

Depending on the hazard rating, the required backflow-prevention device ranges from a simple fit-and-forget dual check-valve to a complex reduced-pressure-zone device requiring regular inspection by a qualified technician. You must ensure that your system is installed, commissioned and tested by a “suitably qualified person”.

It’s all set out in the Standard and the responsibility for getting it right lies with you, the property owner or occupier.

Licensed Plumbers and Testers

Plumbers who install or test backflow-prevention devices must be licensed in backflow according to the standards set by the Plumbing Industry Commission. They must understand the relevant codes and standards for selection, installation, commissioning and testing.

Critically, they must be able to give professional advice about the suitability of specific backflow-prevention devices for individual premises. They also require a clear understanding of the legal responsibilities of installers and testers.

Overwhelmed? Can We Help?

At Reliable Plumbing, we employ qualified and accredited installers and testers for backflow-prevention devices and we can help you comply with your legal obligations. Remember, we’re only a phone call away. If you need further information or advice, call us on 1300 78 20 40 any time. We’re there to help.