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Tank Standards

AS/NZS 4766: 2020 is the Australian & New Zealand standard written for polyethylene water tanks to ensure they have been properly designed and manufactured to be fit for purpose.  Compliance to this standard is a requirement for most water storage tanks installed into new homes or when rebates have been applied to subsidise the cost of the tank and/or its installation.  A certification mark will confirm that a third party has checked and verified the product guaranteeing each condition of the standard has been met by the manufacturer.  We recommend you purchase a tank that has been independently certified as this will give you peace of mind and confidence that your water tank is of the highest quality.  As of yet, there are no standards written specifically for steel or concrete water tanks.


It is important to note that not every manufacturer chooses to certify their products.  With or without certification, every tank must comply with the specifications of the standard in order to meet the industry's best practice requirements.  If you are unsure whether or not your tank is certified, the following checklist will help you identify some problem areas that may help determine the overall quality of your tank.  If it appears your tank does not comply with the standard, we recommend you contact the manufacturer asking for confirmation of compliance.  If you need any help or would like us to check on your behalf, please contact us.


Checking Compliance


The curved edge at the bottom of your tank is known as a knuckle.  The radius of this knuckle should not be less than

25mm for tanks with a diameter less than 1.8m and 38mm for larger tanks.  The minimum thickness of the knuckle

radius should not be less than the maximum thickness of the cylindrical walls of your tank.


Wall Thickness


The thickness of the tank wall must be calculated by a professional engineer.  The vertical wall thickness and that of the roof should not be less than 4.5mm at any location.  The thickness of the floor should not be less than 3.5mm at any location.


Tank Capacity


The capacity of your tank should not be less than its stated capacity.  The internal volume is calculated with the tank unfilled and  in a vertical position.  The height of the tank is from the base to the invert level of the tank's overflow.  Alternatively, you can determine the capacity by filling the tank and measuring the quantity of water needed to fill it to the invert level of the overflow.  




Fitted screens should comply with the rules and regulations of the state or territory to which it is sold.




At the time of manufacture, the finished tank surface should be free from visible defects such as foreign inclusions, air bubbles, pinholes, or cracking that may impair the serviceability of the tank.  The surface of your tank should be smooth and have a homogeneous appearance.  It should not be glossy or discolored on the inside.















Your manufacturer should provide detailed instructions for the installation of the tank either on the tank itself or as a

hard copy.  These instructions will be individual to the design of the tank and should provide, at minimum, the

following information:

a) site selection criteria

b) site preparation details

c) plumbing connection instructions


Marking Requirements


Your tank should be legibly and permanently marked on the external surface of the vertical wall where it can be easily 

seen from its installed position.  These markings should include:

a) manufacturer's name or registered trademark

b) tank capacity, based on the criteria described above

c) maximum specific gravity of the contents of the tank

d) maximum design surface temperature e.g. 23°C

e) date (month and year) of manufacture

f) serial number

g) if the tank does not comply with AS/NZS 4020 and/or AS 2070, as follows:

     i) not suitable for drinking water and food

     ii) not suitable for drinking water

     iii) not suitable for food

h) number of the standard i.e. AS/NZS 4766

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