Best type of Water Tank
In Australia, BASIX rules make it compulsory for every new house to have at least one water tank, depending on the size of the house as well as the balance of BASIX points that need to be made up.
So what do you do when you’re struggling to stay within a budget? - look for the cheapest tank of course. However, the cheapest tank on the market, Zincalume, is not the prettiest and doesn’t have much of a warranty.
ZINCALUME, STEEL or GALVANISED TANKS
There are some other issues with this tank as well. Zincalume, made from raw zinc plated metal, corrodes quite quickly. In general, these tanks will corrode to perforation within 4 to 8 years. As rainwater tends to be acidic, you’ll be getting metallic water long before this.
Cost 22,000 litre (5000gal) Zincalume tank: $1,700
AQUAPLATE or COLORBOND TANKS
An improvement on Zincalume is the Aquaplate tank – which is made from plastic lined (food grade) galvanised steel. It comes in some attractive colours and blends well with a colorbond roof. The idea of the plastic lining is to prevent corrosion of the metal underneath, but the problem is, the lining can be easily scratched, during manufacturing or cleaning. Furthermore, the lining is not UV stabilised, and is sensitive to sunlight and heat. According to the manufacturers, this tank should not be exposed to temperatures >70 degrees Celsius, meaning the tank lining would not withstand a grass fire or bushfire.
Fibreglass tanks are also lined with this so-called "food grade" plastic lining. Although the lining conforms to Australian Standards #AS2070 - that is, "plastic material for food contact use", that's not exactly what it's being used for. We now know that this easily damaged lining releases bisphenol A (BPA) into the water. This suspected carcinogen and reproductive toxin which has been found in the urine more than 90% of people tested in a recent study by the US Centers for Disease Control laboratory.
Cost 22,000 litre (5000gal) Aquaplate Tank: $2,600
Poly Tanks are made of plastic – usually UV stabilised Polyethylene. They do not corrode, come in range of colours and are extremely affordable. On the down side, they readily absorb heat and as the are usually placed on the Western side of a house to act as a heat sink, the water also heats up. Algae and bacteria love warm water and plastic tanks are always coated with green slime (biofilm) – try leaving filtered water in a plastic drink bottle in the sun for just a few days.
Even UV stabilised plastic eventually breaks down when exposed to prolonged sunlight. As the tank’s colour fades on the outside, the interior is also breaking down, contaminating your water with phthalates (water soluble plasticizers), now known to disrupt the body's endocrine system, and BPA. Plastic infused water tastes pretty bad too.
Cost 22,000 litre (5000gal) Poly Tank: $2,500
Concrete tanks will eventually crack, some within 10 years, and are extremely difficult to repair. Small cracks on the inside of concrete tanks make perfect homes for the dreaded E Coli bacteria, which is virtually impossible to dislodge with cleaning. Lime will continuously leach into the water, making the water more alkaline but not necessarily more healthy. Concrete tanks are sealed with rubber (PVC) to stop water leaking out. PVC is another problem child as it also leaches plasticisers into the water. Unfortunately, our municipal and household water pipes in Australia are also made from PVC!
Cost of Good quality 22,000 litre (5000gal) Concrete Tank: $3,500
STAINLESS STEEL TANKS
Stainless Steel is the safest tank for storing water. It does not require a plastic lining, does not easily acquire a biofilm and does not leach metals, phthalates, BPA or lime into your water. Stainless tanks last the longest – up to 50 or 60 years, and can be readily recycled if need be. Good quality stainless tanks are made from 304 stainless steel and have no rivets or screws.