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AQUAPLATE Steel Water Tanks vs Poly Tanks

When looking for a rainwater tank for your property you will find many tanks on the market that are made from different materials. If you have investigated steel tanks in particular, then rainwater tanks fabricated from BlueScope’s AQUAPLATE® steel is one that you’ve probably stumbled across.

This article aims to provide an analysis of AQUAPLATE steel tanks compared to poly water tanks. What is AQUAPLATE steel? How does it compare to poly water tanks? What are some important differences to be aware of? These are some questions that will be explored below.

What is AQUAPLATE Steel?

Aquaplate Steel Water Tanks vs Poly Tanks

AQUAPLATE® steel is available in unpainted and laminated/pre-painted COLORBOND® steel forms.

In laminated or painted form, the steel is comprised of ZINCALUME® steel hot-dipped in 275g/m2 of zinc. The outer side is laminated or coated with a COLORBOND® colour, while the inner side is laminated with a thin poly coating.

In unpainted form, the product consists of ZINCALUME steel hot-dipped in 450g/m2 of zinc. Different finishes are available for the exterior side, and the inner side is again coated with a thin poly layer to help protect the steel from water corrosion.

What makes AQUAPLATE steel is the paper thin interior coating of food-grade polyethylene which is about one-fifth of a millimetre in thickness.

What are Poly Tanks?

Poly water tanks made in Australia today are often made to withstand the Sun and are safe to use for drinking water. To verify this is the case ensure that your tank is made from food-grade UV-stabilised polyethylene approved to Australian Standards for products used for drinking water (AS/NZS 4020).

Poly tanks are fabricated through a rotomoulding process where plastic resin is heated up, rotationally spun inside a cast and then cooled and allowed to set. Poly tanks are either rotomoulded:

  1. as two pieces that are then joined together through a plastic welding process; or
  2. as one piece without any side seams.

The Australian Standard for polyethylene tanks (AS/NZS 4766) requires that quality poly tanks be rotomoulded as one piece.

There are also other features this standard specifies when building a quality poly tank that will reliably store liquids under Earth’s normal atmospheric conditions. If you are looking into a poly water tank, it is important to ensure your tank is certified to this standard (AS/NZS 4766) and that the manufacturer is also certified for a quality controlled manufacturing process such as ISO 9001.

Poly Tanks and AQUAPLATE Steel Compared

  • Price: AQUAPLATE steel tanks are often a bit more expensive than poly water tanks with about a 25% increase in cost depending upon seller, size and style.
  • Sizes: Larger sized steel tanks can be purchased, whereas poly tanks are only available up to around 50,000 litres but can be joined together.
  • Styles: Both tanks are available in a range of colours and in round and slimline models. Poly tank models are also available for under decks, underground or even partially buried below the surface.
  • Strength: Steel might be harder than plastic, but the thin inner poly lining with AQUAPLATE can be easily damaged during installation or cleaning which then allows corrosion to occur and/or voids warranty. Poly tanks are much more impact resistant where hard objects like a hammer will literally bounce off, whereas steel tanks will become dented and require repair.
  • Corrosion Resistance: AQUAPLATE cannot come into direct contact with moisture, and chemical agents and other substances or corrosion will occur. This includes soil, ash, fertilizer, moisture-retaining substances, lead or copper of other dissimilar metals sometimes found in roofs, gutters or fences, water from copper flashings or copper pipes, green or wet timber or treated timber. Poly tanks that are UV-stabilised will withstand the Sun and plastic also obviously does not rust. So you have less to worry about with a poly tank.
  • Warranty: Depends upon the model of tank, but AQUAPLATE steel often carries a 20 year warranty, and poly tanks can be found in warranty up to around 25 years. Important to note, AQUAPLATE steel carries a detailed list of conditions to be aware of to avoid your warranty being voided. Ensure you compare the warranties between the tanks you are deciding upon carefully.