Tanks for the Advice – A guide for Rainwater Tank Retailers

Helen Tuton from Sustainable Gardening Australia has contributed this retailers’ guide, to ensure you’re equipped to help customers make the right decision when it comes to purchasing rainwater tanks. Read the breakdown of commonly used, currently available rainwater tanks and their features. Oh, and remember to point people towards licensed plumbers for installation (or make installation a value-added service offered by your store) as it’s the only way to claim Government rebates on the purchase price.

Retailers Guide to Tanks

Bladder Tanks

Size/Capacity Range: 300L – 20,000L

What’s it made of? Flexible reinforced PVC (Polyvinyl chloride) geomembrane

What’s the deal? Essentially, bladder tanks are like large, water filled wine casks. The inflatable tanks are designed to be located on top of the ground, under the floors or decks of houses, and are essentially long and thin, perfect for sitting between stumps and foundations. Many of these types of tanks are enclosed in a steel or metal frame and storage capacity can be increased by installing a number of these tanks in sequence (space permitting). Why we like it: They are fairly cost effective and more easily transported. Bladder tanks are also a great option for people who have difficulties with access for larger, rigid tanks (bladders can be rolled up and carried through the house!). They slot away nicely ‘out of sight’ under the house, which has the added bonus of making it easier to direct downpipe water to them.

Why we don’t: They are pretty tough, but are definitely not unbreakable (or untearable), and users run the risk of voiding the warranty on a few brands if they are exposed to direct sunlight too long. All of them need an under house clearance of 750mm as a bare minimum, and installers must make sure the tank is not blocking access to utilities (like S bends and underfloor piping). Oh, and as they’re like a water filled jumping castle, some serious kid-control is required!

Environmental footprint and overall sustainability: Like all tanks, it’s important to have a look at the warranty period. Many bladder tanks have fairly limited warranty lengths (about three years), which isn’t great, and this means there is the potential for a great deal of PVC to end up in landfill in a relatively short space of time. This is made more significant by the fact that PVC can take a long time to degrade, and even then it just ‘granulates’ (big bits become smaller bits). In fact, PVC is often regarded as a contaminant in many waste streams, and less than 1% is recycled, or able to be recycled. The manufacturing process is another issue, with key ingredients being oil and chlorine, two products with really big environmental footprints. It has to be said, while these tanks are cheap, the long term cost to the planet may far outweigh the potential savings.

Poly (Plastic) Tanks

Size/Capacity Range: 600L – 50,000L

What’s it made of? Food Grade High Density Polyethylene (HDPE)

What’s the deal? Available in a massive range of colours, shapes and sizes, they are the plastic equivalent to the traditional Aussie corrugated tank. There are a load of companies manufacturing these, both in Australia and overseas, so be sure you know where your tank range was made and what the warranty period is. (And don’t forget the potential to upsell to products with longer warranties.) Why we like it: The flexibility in colour and size is astonishing, with one to suit just about every property. Got a customer with a smaller landholding? Don’t worry. Poly tanks are now available as flat, ‘wall’ type tanks, designed to run along property boundaries, the side of the house, shed or garage. And the price is pretty decent, even if round tanks will always be cheaper than a wall type tank of the same capacity.

Why we don’t: Some unscrupulous operators are flogging inferior foreign tanks, manufactured to a different (much lower) food grade level than Aussie-made tanks. Inferior plastic moulding + two tonnes of water = potential disaster! Unlike bladder tanks, poly tanks need a base specially prepared before they are installed. Generally, a crushed rock and sand base is recommended for the round units, while wall style tanks can normally sit on a flat, stable concrete or tiled base. Freestanding wall tanks often need to be braced to something to prevent them tipping over when full, so remind customers to check the strength of their bracing structure (eg: the fence or shed) before attaching. The only thing worse that a tank tipping over is one tipping over and taking the shed or fence with it. Oh, and for folks in bushfire areas, an added issue is that plastic tanks do not perform well in the heat of a fire event.

Environmental footprint and overall sustainability: HDPE tanks have a pretty negative environmental impact, due to their high embodied energy and the greenhouse gas emissions from the manufacturing process. Non-renewable fossil fuels are used in the manufacture of plastics (including HDPE), which also gives them a bit of a thumbs down. That said, their embodied water (the amount of water used to make them) is pretty low, especially in comparison to some other types of tanks. Can these tanks be recycled? The jury is still out at the moment, mainly due to the possibility that long exposure to sunlight has the potential to render these tanks un-recyclable.

Steel Tanks

Size/Capacity Range: 300L – 20,000L

What’s it made of? Corrugated Steel (often lined with a polymer)

What’s the deal? These are the quintessential Aussie tank, the corro number many of us grew up with. They have had a serious facelift in the last few years and are now available in a range of colours, sizes and even shapes. Although there size range can be somewhat limited, they are pretty good looking – and the range of colours allows them to fit quite nicely into most domestic settings. Why we like it: Instead of being hidden away behind the back of the shed, steel tanks can make a great (and useful) feature in gardens. Due to their smaller size, they are easier to manoeuvre, and many come with their own stand, negating the need for preparation of a special base (as long as they’re placed on a level surface).

Why we don’t: These tanks can corrode over time. Smaller sizing means that, in order to be useful, users may need to install more than one. And they can be fairly expensive when compared to other options. Environmental footprint and overall sustainability: Steel tanks have the lowest environmental impact of any type of modern tank, due to the low embodied energy, greenhouse gas emissions, embodied water and nitrous oxide emissions during manufacture. To be truly sustainable, make sure your range includes a locally manufactured steel tank, to also cut down on transport related emissions. The planet (and your sustainably-minded shoppers) will thank you.

Concrete Tanks

Size/Capacity Range: 3,700L – 500,000L

What’s it made of? Concrete (with internal steel reinforcement)

What’s the deal? They’re big, heavy, (generally) built onsite and can have a massive capacity. Why we like it: The biggest advantage to concrete tanks is their larger capacity. Essentially, concrete tanks can be hand built (or pre-cast) to just about any size, from about 3700L to 500,000L. They can be installed either under or above ground (and can be painted). They are wind, vermin, sun, fire and rust proof, and the concrete keeps the water cool, clean and algae free. They can also often be repaired if damaged.

Why we don’t: Well, admittedly they are pretty ugly and, even when installed underground, the large access area and tank roof is still quite visible. Being concrete, they are porous and can occasionally crack. They have a pretty limited warranty period (about 15 to 20 years) and, if used for drinking water, may need to be flushed out several times to get rid of the ‘taste’ of concrete.

Environmental footprint and overall sustainability: Concrete tanks are generally considered to be a bit of an environmental nightmare, based on a number of lifecycle assessments conducted by respected universities and organisations. For one, they’re manufactured with both concrete and steel, meaning their inputs are pretty high. In fact, a 5000L concrete tank has about 160kg of steel reinforcement (and weighs about 2600kg all up). This means that, of all the commonly available tanks, concrete models have the highest embodied water, embodied energy and greenhouse gas emissions. There is also often a large environmental impact associated with their transportation, due to the associated weight and the fact that they cannot be stacked in transit. On the flipside, there is the potential to recycle elements of the tank at the end of its useful life, particularly the steel framing.

For more top notch info on sustainable rainwater capture, visit www.sgaonline.org.au.