Backflow is when water flows the wrong way and contaminates the clean supply. Devices stop this from happening.

How it happens

A drop in mains pressure can pull water back from a garden hose in a dirty pool or a tank.

Where devices are used

Irrigation systems, rainwater tank connections, fire services and some commercial sites.

Testing

Many devices need regular testing by a qualified plumber.

Cost of skipping it

Contaminated water is a health risk, and some properties have to meet testing and maintenance requirements for their backflow devices. Your water retailer and the Victorian Building Authority explain which rules apply.

Ask us

We can check what your property needs.

Types of backflow devices

There are several types, from simple dual check valves on a hose tap to testable devices on irrigation and commercial lines. The right device depends on the level of hazard. A low hazard might be a garden tap. A high hazard might be a chemical dosing system.

Why it matters at home

Leaving a hose in a pool or a bucket of fertiliser and then having the mains pressure drop can pull dirty water into the house supply. A hose tap vacuum breaker is a cheap fix.

Testing and records

Testable devices usually need yearly testing by a qualified person, and the results are recorded. Ask your plumber what applies to your site.

Irrigation systems

Garden irrigation connected to mains usually needs a backflow device. Fertiliser injectors and chemical additives raise the hazard level.

What we can do

Ask your plumber what backflow protection your property needs, and whether any device needs testing.

Does your home need one?

Some taps and fittings include a basic backflow device, and a plumber can tell you what your property has. The ones that matter most are on irrigation systems, fire services, pools, rainwater tank top ups and anywhere a hose can sit under water. If you have a garden irrigation system or a tank connected to the mains, ask your plumber whether the right device is fitted.

Some devices need testing at regular intervals, and the rules depend on the hazard rating of the site. Commercial properties often have stricter requirements than homes. If you are unsure, ask your water authority or a licensed plumber what applies at your address.

Practical backflow habits at home

You can reduce risk without any special gear. Do not leave a hose end under water in a pool, bucket or pond. Do not connect a hose to a chemical sprayer without the right device. Do not connect a tank directly to the mains. If you have irrigation, make sure it has the right device and that it has been tested when required.

If you are not sure what you have, ask a licensed plumber to look at the connections around the meter and irrigation. It is a short job, and it protects your own household water as well as the street supply.

What backflow actually is

Your home is supplied with clean drinking water under pressure. Normally that water only moves one way, from the street main into your pipes. Backflow is when it moves the other way. It can happen when there is a sudden drop in mains pressure, for example during a main break or when a fire crew draws a lot of water nearby. It can also happen when the pressure on your own side is higher than the mains, such as a pump or a heated system pushing water backwards.

When water flows backwards, whatever the pipe is connected to can be pulled into the supply. A hose sitting in a bucket of pesticide, a pool, a fish pond or a dirty trough is the classic example. That is why the rules are strict about connections between drinking water and anything that could contaminate it.

Everyday places it matters at home

Most homes have a few spots worth checking. Garden hose taps are the most common. A hose left lying in a puddle, a pool or a bucket can siphon that water back into the pipes if the pressure drops. A simple hose tap vacuum breaker screws onto the tap and costs little. Other spots are toilet cisterns with faulty inlet valves, bidets and handheld sprays that can sit under water, and irrigation systems that connect to the mains.

Never leave the end of a hose under water, and do not use a hose to top up a pool without a proper air gap or approved device. If you have a rainwater tank topped up from the mains, the connection needs an air gap or an approved device so tank water cannot enter the mains supply.

Business and larger sites

Commercial properties carry a higher risk. Cafes, car washes, salons, medical practices, farms, workshops and anywhere that uses chemicals or has fire services need to think about backflow. The device used depends on how dangerous the possible contaminant is. Testable devices, such as reduced pressure zone valves, are used where the hazard is higher and they need to be tested regularly by a qualified person.

If you own or manage a site like this, ask your plumber to list the backflow devices on the property, when they were last tested, and what is due. Keep the test records. Water authorities and insurers can ask for them.

Signs a device is not working

A valve that drips continuously from its relief port, water hammer, a change in pressure, or a device that has never been tested are warning signs. These devices have moving parts that wear. Debris in the water can stop the seals closing. Frost and heat can damage them. If a device is dripping, do not block the relief port. It is meant to release water if something fails. Call a plumber.

Next steps

If you are not sure whether your home or business needs a device, call us. We can walk through your taps, irrigation, tanks and any chemical connections and tell you what is needed in plain terms. For testable devices, we will explain what testing involves and how often.

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