Lined Steel water tanks vs Poly

Should I purchase one single Steel water tank or multiple Poly tanks?

Are you looking to purchase a rainwater tank for your home and need to make a decision regarding what type of tank to buy? Working through this can be confusing due to the variety of different rainwater tank options available. Hopefully we can can help you make the right choice of water tank for your needs.

Determining which size tank you will need to suit your needs is important. An average family uses approximately 219,000L of water per year in the household (Excluding the garden). In order to provide at least this volume of water, you will need a minimum tank holding size of 110,000l, assuming a 750mm rainfall, with a roof catchment area of 350m2 (Average home and shed). These variables can be vastly different in the wide range of climate zones we experience in Australia. If you would like to learn about how much water you can catch each year in the rainfall zone where you live, you can use our online Harvest Calculator or visit the Tankulator website to calculate your household water demand and capacity to harvest water.

Why have this?

Water bottles

When you can have this

Pale Eucalyptus water tank

One tank instead of multiple

The maths is pretty simple to understand and so are the benefits. If you purchase a 110,000L Steel-Liner water tank, you will need to purchase at least 4 Poly tanks to come close to being able to harvest and store the same volume of water each year. With an approximate cost of $4,000 for an average 25,000l Poly tank, you would need to outlay $16,000 for 100,000l storage capacity, whereas a lined-Steel tank of 110,000l will set you back approximately just over half of this amount!

Poly vs Steel

As you can tell from the table, the smaller tanks are more commonly manufactured with Polyethylene as it’s light and can be made relatively cheaply. For tanks between 1,000 Litres and up to 17,000 Litres, a poly tank is often your best choice and will set you back between $500 and $4,000. Things get a bit more complicated as tank sizes increase and this is where lined steel tanks become the more logical and common choice, particularly in high fire risk zones. Read more about Managing your water tank in a bushfire situation HERE.

The reason for this is is that for tanks up to around 17,000 litres, the price per litre of poly water tanks decreases as they get larger, as you might expect. At around this range, as tank sizes increase, the scales tip back the other way and the cost of poly tanks actually begins to rise again, making steel the better choice.

The main reason for this is the logistics and complications related to transporting tanks to site. Poly tanks in excess of 24,500 litres are considered oversize loads in many places in Australia and this places an increasing cost on delivery. Also, Poly tanks are made in moulds and it becomes impractical and expensive to manufacture moulds over a certain size.

Steel tanks, on the other hand are transported on a flat-pack pallet and are fully assembled on-site, which makes them easy to get to even the most remote and inaccessible sites.

Fire Resistance - Poly vs Steel

No tanks are completely fire-proof, however, steel tanks offer better fire resistance than other products. Low heat bush-fire exposure can make steel tanks turn black on the outside, however, many steel-liner water tanks have remained intact when exposed to bushfire incidents throughout Australia.

Of course, prolonged exposure to high temperatures (such as experienced in an extreme fire-front) will eventually destroy most water tanks, depending on how much water is in the tank and the intensity of the fire.

Plastic tanks are known to catch on fire when there is a sustained ignition source, such as in a high intensity bush fire. Also, plastic-coated steel tanks, contrary to what some tank manufacturers state, are also sensitive to temperature. In an intense fire, the plastic coating inside the tank will separate and render the tank useless.

In research conducted by the CSIRO into Fire Impact, steel liner tanks performed better than Aquaplate®, with the steel-coating melting at about 200 degrees and fibreglass tanks also failed extensively.

Heritage Water Tanks are designed to resist damage to their structural integrity and retain water during and after exposure to a fire front. Examples of this were observed following catastrophic bush-fires in Victoria in 2009.

Lined steel water tanks are seen more and more widely in rural, domestic and commercial and industrial contexts and are available in all sizes, from smaller household tanks from 17,000l, through to tanks of up to several megalitres.

Prices - Poly vs Steel

For a quick overview, we’ve put together the table below which will give you a ballpark number for different tank sizes. It’s important to note, however, that prices do vary based on a range of different factors such as the location of installation, colour and fitting selection.

Size Best Material Useful for Average Starting Price **
1,000 Litre Poly Small households $500-$1,000
5,000 Litre Poly Small households $800-$1,500
10,000 Litre Poly Small households $1,700-$2,500
25,000 Litre Steel Small households $3,000 - $4,000
55,000 Litre Steel Low demand rural $6,500
110,000 Litre Steel Medium demand rural $8,500
160,000 Litre Steel Medium demand rural $11,500
220,000 Litre Steel Medium/high demand rural $15,000
250,000 Litre Steel High demand rural $16,000
285,000 Litre Steel High demand rural $19,000
375,000 Litre Steel High demand rural $22,000

** Actual price will vary depending on State and location of installation. For an accurate price, talk to one of our sales advisors or request a quote online.

Superior ARMA Liner

All tanks intended for storing potable water, including steel tanks with plastic liners must be constructed of materials that are food-grade. For domestic use, materials that come into contact with water must be compliant with Australian Standard AS2070, ‘Plastic materials for food contact use’ and AS/NZS4020, ‘Testing of products for use in contact with drinking water’. See our AquaFresh Liner information. Heritage Water Tanks’ liners are made of chemically inert material, with exceptional strength, durability and elasticity and retain these properties for greatly extended periods of time, even under the most harsh environmental conditions.

This is why out tanks are so well suited to the harsh climate and extreme temperatures experienced in much of Australia. Not only can our tank materials stand up to rigorous lab testing, but they also stand up to the true Aussie bush test, performing outstandingly well on many pastoral stations in central and northern Australia.

The Heritage Water Tanks Arma Liner is manufactured to the highest standards. In independent testing, our liners were rated on lineal weight or weight per square metre, which is a measure of density. Our liners weigh 700 g/m², where our closest competitor’s liner weighs under 500g/m². See the comparative test results here

This testing identified our ARMA Liner as the best in relation to Shear Strength, Tear Strength and Density, compared to the liners of our competitors at that time.

Independent liner test results:

Heritage Water tanks – ARMA liner

For more information about this testing, please view our YouTube video here: ARMA liner independent testing

Steel Tank Walls

Our walls are made from proven, highly corrosion resistant, long lasting BlueScope Steel. The steel used in the production of our water tanks is a minimum of 1mm bmt, which is thicker than material used by most of our competitors. Our wall profile was also designed in consultation with engineers to provide superior strength and exceptional durability.

Value for money and Warranty

Some tanks may be cheaper upfront, but lose out on durability, so are more expensive in the long run. Even if the upfront price exceeds a cheaper alternative, it’s important to look at the overall lifespan of the tank. If you’re going to be needing to pay for another water tank in 10 years, it’s probably better to invest the extra money for something that will last for over 20 years.

Heritage Water Tanks offers a 20-year pro-rata conditional warranty. This means that we will replace the cost or repair of any of your water tank parts covered under the warranty terms and conditions. Most Poly Tank companies only offer a 10 or 15-year warranty at best. You should also be careful of ‘Too good to be true,’ product warranties that some water tank companies sometimes offer. Whilst a longer 30 year Warranty might sound good, often the conditions state that the value of the repair or replacement of the components is based on the price that as paid at the point of sale, therefore in 30 years time, your Warranty will not be based on the current value of the item being replaced and will be virtually worthless.

Other subjects you can learn about on our website include: Selecting a site for your tank, where to place your fittings, independent liner testing, water tanks sizes and much more.

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To find out more about our special offers, please call 1800 155 552