It should be noted that fire services installed before May 2010 were not required to have installed a boundary device unless the fire service was being altered at the property boundary.

For maintenance and testing purposes, isolation valves must be located either side of a testable backflow prevention device.  A line strainer is also required to be installed upstream of the device (except on fire service installations).  Isolation valves installed on services of 80mm and larger must be gear activated.

Power and Water Corporation is committed to providing safe drinking water (potable water) to their customers.  Part of the process to providing safe drinking water involves analysing the various hazards to the safety of the water supply and ensuring that there are barriers to control or eliminate those hazards.

The rating for risk of backflow is normally advised at the time the building development application is approved.  The final risk rating may be determined by the activity of a specific site survey.

High Hazard – Any condition, device or practice in connection to a drinking water supply system has the potential to cause death.

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The policy ensures that appropriate site containment backflow prevention devices are fitted to drinking water supply for the protection from unintended cross connection and backflow of contaminants into the drinking water supply system.

Normally a family bottle of water should work (5 or 6 liters). A drum is another option but I suggest you to get a transparent one for simplicity of testing it.

This Standard specifies requirements for the design, performance and testing of backflow prevention devices, used for the protection of potable water.

If a building does not have a backflow prevention device installed it is the owner’s or occupier’s responsibility to ensure one is installed.  Check your risk rating and arrange to have an appropriate backflow prevention device installed.

The Office of the Technical Regulator Plumbing (OTR) manages backflow prevention to meet the AS/NZS3500 Plumbing and Drainage Standards.  For further information visit www.sa.gov.au/otrplumbing or call OTR on 1300 760 311.  The information in provides an overview of SA Water and customer obligations to protect the public water supply.

Based on the assessed hazard rating, a suitably rated backflow prevention device must be installed immediately downstream of the drinking water connection.  The device will need to be supplied and installed by a licensed plumber.

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Since you need to place reed switches inside so for this 3d printed cap to work in needs ~11 mm inner diameter but you can seal it with any other thing really.

If a bore pump is cross-connected to the internal water plumbing system and the pump is at a higher pressure than the water mains pressure, a backflow can also occur.

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“Water distribution systems should be fully enclosed and storages should be securely roofed with external drainage to prevent contamination.  Backflow prevention policies should be applied and monitored.  Also, there should be effective maintenance procedures to repair faults and burst mains in a manner that will prevent contamination.  Positive pressure should be maintained through the distribution system.  Appropriate security needs to be put in place to prevent unauthorised access to, or interference with, water storages.”

https://www.sa.gov.au/topics/water-energy-and-environment/electrical-gas-and-plumbing-safety-and-technical-regulation/plumbing-trades/plumbing-installations/backflow-prevention-requirements

The Office of the Technical Regulator in the SA Government authority specifies the test report format required.  The Commission Inspection and Maintenance Report is the form required and is online from their website.  This is the only acceptable form and must be saved on your computer if you want to retain the data.

Service providers usually determine their own backflow prevention requirements to protect their water supply system, but check with government offices in your State and the appropriate regulations to clarify specific responsibilities.

So here we are, a simple level indicator using magnets. From here there are countless things you can do with it, the only thing I do not recommend is to drink this water since it will be in contact with glue and 3d printed plastic, but there are many other things to try and play, I'll be working on some projects using this, if they make sense to share I'll be creating a second instructable.

Further information can be obtained from the Power and Water Corporation authority (PowerWater) in the Northern Territory on 8951 7312 (Southern Region) and 8995 5801 (Northern Region).

Protection of the potable water supply from backflow contamination and to ensure it is safe to, requires backflow prevention devices to be installed at the property boundary.

Most common way is using the water as a conductor, so if there is water between 2 wires you will get the close circuit, but main problem on conductive indicators is the water must have salts cause that's what gives the water the conductivity and that wasn't working for me because one of my projects was to have an alarm inside my disposal bottle of my air conditioner when it was full but since that water is from condensation it has no conductivity at all :(

Fire hose reels may also require backflow protection dependent on the risk rating as assessed by the plumbing contractor or qualified person.

Normally applications to build include an assessment for backflow prevention at the time of application.  But you should check yourself that this assessment has been included.

For new water connections, or when alternate water supplies have been reticulated to or within the property, the owner of the property, or responsible entity, must engage a qualified contractor to assess the proposed use and potential hazard level of the proposed on-site activities, in compliance with AS/NZS3500.1 (eg, low, medium or high hazard).

A buoy (which has magnets inside it) will float in water which means it will be keeping magnets at water level and since we have a Reed Switch (at some specific height inside the pipe) it will be activated (closing or opening the circuit) and if we know how many liters are at that height we know how much water is in the bottle.

These Guidelines are published by the National Health and Medical Research Council and provide an authoritative reference for safe, good quality water, how it can be achieved and how it can be assured.  The Guidelines are concerned with safety from a health perspective and with aesthetic quality.  The Guidelines require backflow prevention policies to be applied and monitored as a preventative measure to maintain the integrity of the system and to protect water quality.

You can use an independently suitably qualified licenced plumbing contractor or hydraulic consultant and lodge an appeal to the Water Corporation.

A person must not pollute with any substance a reservoir, dam, reservoir or dam catchment area, groundwater recharge area, bore, borefield, aqueduct, water storage tank or infrastructure that is used or constructed to hold or supply water for human consumption.

Low Risk – where the water supply system poses a nuisance but does not endanger health or cause injury. Medium Risk – where the water supply system could endanger health. High Risk – where the water supply system could cause death.

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All properties connected to the public water supply system must be assessed to determine the level of the hazard the property presents to the water supply system. Australian Standard 3500.1 has the following hazard rating system:

The reversal of the normal direction of water flow in a water supply plumbing system is called backflow. This occurs as the water delivery main is at a lower pressure than the internal plumbing system (back siphonage). This can occur where there is a burst or rupture in the water main, due to excessive demand during fire-fighting or other high demand situations.

The Hunter Water authority has the policy to ensure they exercise their required duty of care for the protection of the drinking water supply system and the safeguarding of public health.

For drinking water connections 25mm or larger a plumber must assess the hazard rating of onsite activities and install a suitably rated backflow prevention device.  The backflow prevention device needs to be situated at the property boundary adjacent to the water meter.

A mechanical way is another option; we all have seen that inside our bathrooms, almost every toilet flush system works with a mechanical switch which consist in a buoy that closes the water entry. This method was a good approach but I wanted to keep my current simple bottle without having to create huge modifications on it by cutting it out and then having to seal it.

Our final step is to get a visual signal for testing the device, it can be anything I've chosen leds cause it's the easier and faster way of doing it, but normally this is a first step to a bigger project where we will be doing something with that signal and a led won't help much in there.

The hazard rating and backflow prevention requirements for a property may change if another water supply is present or there is a change in the onsite activity.  The level of protection will need to be  Assessed by a licensed plumber

The completed report and the certificate of compliance must be sent to the Office of the Technical Regulator by the plumber within seven days.  All fields are mandatory for completion with the Plumber’s, Gas Fitter’s or Electrician’s number quoted.

Regulations exist with penalties of up to $5,000 and $500 per day for incidents where the need to fit backflow prevention devices have not been complied with.

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Licenced plumbing contractors with appropriate accreditation are the only persons who can install backflow prevention devices.

Offences can also result in the restriction or disconnection water services.  The protection of the drinking water supply is paramount.

A note: notebook HDD magnets didn't work for me I guess they don't have enough strength, so use a desktop pc HDD magnets

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Connections here are pretty straight forward, one common cable for all reed switches and another on each end, if you choose to use 5 reed switches you will end up having 6 cable ends.

I have placed instructions on each pic here, the most important thing is to seal the buoy since we need air inside for it to float so don't be cheap on the hot glue and fill every gap on outside

NT’s Power and Water Corporation Customer Handout No 7 provides a brief overview of the backflow requirements for government agencies, developers, consultants contractors, property owners, business owners and people involved in the water industry.

An important thing, there is cap at the bottom of the pipe because we don't want water to be inside the pipe, the main idea of this method is to not use the conductance of the liquid to measure. Having water inside the pipe could lead into false indications by bypassing a reed switch.

I went a little overkill here with the amount of reed switches, my first idea was to test this method by placing a reed switch per liter (distance of 5 cm in that bottle) and I could tell the half state by getting 2 sensors activated at same time, so in short I could know every half liter the water level.

If you feel the risk rating for your property is higher than site-specific activities carried out you may appeal that rating.

That's when I came across those simple buoy switches that uses Reed Sensors inside; keeping in mind that I wanted a simple solution I came up with this concentric pipe which holds reed switches inside it and has a moving buoy with magnets attached.

I used magnets taken from an old hard drive breaking just one will give you the 2 magnets needed here which I later split each at half having a total of 4.

The South Australian Government water, energy and environment authority has a concise backflow prevention requirement on their website. It follows the AS/NZS 3500.1 Standard, the national plumbing standard.

“Despite anything in the Act, a licensee does not have an obligation to connect or supply water supply or sewerage services to a customer’s premise if the connection or supply is, or needs to be, interrupted –

The Office of the Technical Regulator in SA Water audits the test kits for backflow prevention.  Because these kits are precision instruments they need to be treated with appropriate care.  Hence the instruments need to be calibrated and certified every 12 months.

Another instance of backflow can be where a property drinking water supply is inadvertently connected with a source of pollution allowing these pollutants to enter the drinking water.  The overpressure at the private property side (for instance a swimming pool) forces the pollutant into the lower pressured drinking water supply.

Medium Hazard – Any condition, device or practice in connection to a drinking water supply system has the potential to endanger health.

For my experiment I've used 5 switches at 5 cm of distance from each since for this Bottle each liter is 5 cm of height.

Backflow Prevention is required for all builders and developers.  The installation of an approved backflow prevention containment device at the boundary of every water service connection to a property (including fire services) is specified in Australian/New Zealand Standard 3500.1.

Low Hazard – Any condition, device or practice in connection to a drinking water supply system constitutes a nuisance but does not endanger health.

Everyone has the right to clean uncontaminated water. Contaminated water can be the result of a backflow incident and can cause health problems or even death. Legislation requiring the installation of backflow prevention is:

SA Water’s new 20mm drinking water meters contain a low hazard (containment) backflow prevention device  (dual check valve) installed in the meter assembly.

This Standard specifies requirements for air gaps and break tanks used as backflow prevention devices for the protection of potable water supply.

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The only restriction is size cause it has to fit inside the buoy which has 4 places of size 2 mm x 10 mm x 15 mm height. If you're buying magnets I recommend you to have the buoy in your hand first.

PWC’s Back Flow Prevention Policy and Backflow Prevention Manual specifies requirements for the installation, maintenance and testing of backflow prevention devices for new and existing services.

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The domestic Power and Water Corporation (PWC) in the Northern Territory has a Backflow Prevention Policy that aims to provide good quality, safe and reliable drinking water;  similar to many other States in Australia.  This Backflow Prevention policy:

Builders or developers who have been advised at the time of application of the backflow risk rating should advise the owners or occupiers of their property’s initial backflow risk rating if customers are unsure of the rating process.

Fire services must have a single spring-loaded testable check valve with certified resilient seated gear activated isolating valves installed on either side of the check valve to permit maintenance and testing. The valve must be installed on the internal pipework within 3 metres of the property boundary in accordance with plumbing installation standards.

Serious risk exists in most major water supply systems with the possibility of backflow of contaminated water from hazardous sites into the potable water supply system.  Backflow events in Australia and overseas have previously resulted in fatalities and serious cases of poisoning.

What I did was to get a network cable and took 6 cables from inside (they have 8 in it). Measure the height you want to get your reed switches at and solder them like the picture trying to keep them vertical along with the cable, so it will be easy to insert into the pipe.

Cross connection is defined as “a connection to the PWC potable water supply from an alternative water supply that may enable non-potable water and other substances to enter the drinking water system”

There are sections within the WSSSA that are relevant to the implementation of backflow prevention. The first relates to the potential pollution of the water supply. The second relates to the specific cause of pollution via cross-connection allowing the potential for backflow. The third relates to circumstances where a backflow hazard may or does exist.

Contact the Service Development Section of the PWC for a copy of their Connection Code and associated activities.  Included is the asset creation process and Backflow Prevention Policy for the Corporation’s water supply and sewerage infrastructure.  The Connection Code and Backflow Prevention Manual internet pages are also available on their internet site.

You don't need to go that precise, you can put 1 or 2, at bottom and top to know if is full or empty, the cool thing is you can get a switch at any level you want without destroying the bottle!