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April 18, 2019

Why Rotational Moulding of Poly Water Tanks is a Big Deal

Agriculture, Water Tanks

<span id="hs_cos_wrapper_name" class="hs_cos_wrapper hs_cos_wrapper_meta_field hs_cos_wrapper_type_text" style="" data-hs-cos-general-type="meta_field" data-hs-cos-type="text" >Why Rotational Moulding of Poly Water Tanks is a Big Deal</span>


It has been said before, that the very fact that poly water tanks are made using rotational moulding gives them a huge advantage over other types of water tanks like steel and fibreglass.


But do you know exactly why?

We decided to make a comprehensive list of the full spectrum of advantages roto-moulded poly water tanks provide that its counterparts couldn’t. It’s almost unfair!

What is rotational moulding of poly water tanks?

In a nutshell, rotational moulding, or rotomolding, is the process of creating durable products made of plastic by ‘cooking’ raw polyethylene material (which is in powder form) in a hollow mould that rotates around two axes.




Low Linear Density Polyethylene (LLDPE) is the main ingredient of Coerco poly water tanks and is responsible for their one-piece construction. LLDPE produces flexible and impact-resistant water tanks that stand the test of time.

Raw material polyethylene undergoes a period of heating during rotation, gradually transforming the powder inside the mould into plastic that sticks to the walls, eventually forming a water tank. The water tank then goes through a period of cooling before it’s ready to be taken out.

There are other types of moulding technique like injection moulding and blow moulding. However, when it comes to constructing poly water tanks, rotational moulding is by far superior.

Benefits of roto-moulded poly water tanks on your farm:


  • Low initial cost on the side of the manufacturer benefits the consumer

On the whole, plastic is less expensive than other types of material used to make water tanks. Additionally, not a lot of equipment or tooling is necessary to produce roto-moulded, seamless poly water tanks. Manufacturing lead time is also significantly reduced as roto-moulding is a straightforward process that allows for a one-piece construction without the need for joints and screws.

All of the above contributes to a low initial cost that is an advantage on the side of the manufacturer, helping them produce some of the cheapest rainwater tanks in the market without necessarily sacrificing effectiveness and durability of the final products.


  • Rust-resistant and corrosion-free

Plastic/poly cannot, and will not, rust. It’s not prone to soil-side corrosion as is common in some types of water tanks. Even stainless-steel tanks are still prone to localised corrosion (which is, by the way, difficult to spot). Joints and screws in stainless-steel tanks are not immune to corrosion either.

The fact that a poly water tank is 100% resistant to rust and corrosion saves you on repair cost in the future.


  • Overall strength

We know it is kind of paradoxical. Poly is lightweight compared to other water tank material - it’s plastic after all – yet it’s also tough. How is this so?

One-piece construction contributes to poly’s impact resistance      

Whereas other types of water tank might easily sustain dents or cracks, poly water tanks are flexible and don’t have a problem bouncing back to shape with impact. Meaning, their structural integrity is maintained far longer than other more expensive water tanks.

Also, parts such as bolts, screws, etc. are themselves prone to damage. These components are like the Achilles heel of steel, concrete and fibreglass tanks.

Wall thickness

One of the things that is responsible for the strength of a quality poly water tank, apart from its one-piece construction, is the adequate thickness made possible by rotational moulding. It's the rotation motion of a roto-moulding machine that ensures all sides of the tank have no weak parts. 


Seamlessness and adequate thickness both contribute a great deal to the overall strength of poly rainwater tanks. 

This strength is in stark contrast to poly’s counterparts like steel and fibreglass, which are thinner and have seams and joints. 

  • Aesthetic strength

Superficial colouring or surface finishes are not necessary with poly water tanks. Colour is added to the polyethylene powder before the roto-moulding process begins. The colour added needs to be durable in the long term.

When the right colour is chosen, the result is a poly water tank that is UV stabilised, possessing colour that doesn’t fade or peel with time even in harsh weather conditions.


  • Greater safety

Roto-moulding helps produce seamless water tanks bereft of any sharp corners or weld parts that might cause injury.

Moreover, Coerco poly water tanks utilise Australian-made materials that pass AS/NZS 4020:2005 testing, which means that they are ideal and safe for storing water intended for human consumption.

12 Critical Mistakes People Make  When Ordering Water Tanks

  • Design flexibility

Polyethylene is one of the easiest thermoplastics to weld. Because of this, modifications are easier to achieve should you require a customised poly water tank better suited for your farm’s needs. Note that fittings and connections must be welded by a certified installation specialist.


poly water tank configuration


  • Environmentally conscious

Plastic, at times, can get such a bad rap. But the truth is that rotomoulding polyethylene is environmentally-friendly. That is, during production of poly water tanks, no harmful substances are released into the environment.

Moreover, polyethylene is recyclable. In fact, Coerco has established a regular recycling program that turns waste polymer material back into poly products.


recycled plastic to be used for poly septic tanks

Polymer material on its way to being recycled to other poly products.


  • Mobility

Coerco poly water tanks are lightweight and easily repositioned and transferred -- something that is difficult to achieve with concrete or steel. This is significant because Australian farming is subject to extreme changes in weather and other rapidly changing conditions that makes adaptability an asset.

Furthermore, because poly is lightweight, the overall cost of water tank installation can be significantly lessened. For example, you don't necessarily need to spend a lot on tank pad preparation because poly doesn't corrode or rust, which means that it can be placed on compacted sand, gravel, and crusher dust. In this aspect, poly rainwater tanks are low-maintenance. 




  • Versatility

Poly water tanks can be set up above ground or underground without sacrificing durability either way. The lightweight quality of poly also aids in the installation process.

Coerco water tanks are also made to adapt to fluctuating Australian climate. Even in high temperatures, Coerco poly water tanks can stand their ground. That is because polyethylene is an insulator which is good at barring heat from the surrounding environment.

Moreover, Coerco manufactures water tanks using only the highest quality, food grade polyethylene. Our vertical water tanks (corrugated, flat walled & slimline) and underground water tanks are made in accordance with Australian standards and boast a 20-year repair or replace warranty.

Related topics: 
Key Differences You Need to Know About Water Tanks
Australian Standards for Reliable Poly Water Tanks
Water Tanks Cost and Pricing Guide

Take your pick among cut-above-the-rest Coerco poly water tanks.  Contact us today. Let’s see how we can help you! 

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