Rainwater tanks can become breeding sites for mosquitoes that can cause severe nuisance and carry serious diseases.  To prevent mosquito breeding and contamination, it is vital guttering and pipework should be self-draining or fitted with drainage points.  Water should not be allowed to pool under the overflow outlet or tap of the tank as these can become mosquito breeding sites.  The tank should be a sealed unit with the lid preventing sunlight from reaching the water.  Sunlight encourages the growth of algae that may taint the water.  A good tank design prohibits vermin from entering the tank by ensuring all the inlets are covered with screening too small to allow them in, however holes and spaces created after or during installation could allow mosquitoes to enter, so be careful.  The inlet should incorporate a mesh cover and a strainer to keep out leaves and to prevent the access of mosquitoes and other insects.  The overflow can also be covered with an insect proof cover such as plastic insect mesh wired around the pipe.  Most government agencies have specific guidelines about the maximum size of mesh aperture allowed.

The material used to manufacture poly tanks is not the same as that used to store water in small bottles (PET), which has been studied by scientists in relation to leaching back into the water.

There is absolutely no evidence that polyethylene leaches any chemicals into the water that could cause cancer.

Plastic tanks have no seams.  Lines that may be visible on the outside of the tanks and look like joins are actually where the two parts of the mould join together, however the product itself isn't made from two sides joined together, but rather one solid piece. Steel tanks and many concrete tanks are made by joining sections of the material together, creating one or more seams.  This is the weakest part of the tank and thus is more prone to damage or splitting.  In steel tanks, the seam is created and may be repaired by soldering.  Concrete tanks will require a sealant to repair any cracks or splits.

There are tanks that have been giving loyal service storing liquids for over 30years, however there is no definite "life" period for a water tank.  As with any other product you buy, its "life" will depend on how you install and maintain it, after it leaves the factory and what the service environment is like. Most tanks will far outlive their warranty period, however the Australian & New Zealand Standard for poly tanks requires a design life of 10 years minimum.  Steel tanks typically come with a warranty of 10 to 20 years while the concrete alternatives will last between 20 and 30 years.

If you are in a rural area, or even the urban fringe, you should take into account the effects of bushfire on your water tank.  Contamination of tanks from floating ash can be a big issue, and a first-flush device can reduce this problem considerably.  Poly tanks can melt down to the waterline if a bushfire gets too close, but in severe fires even metal and concrete tanks can become unusable, so if you are in a fire prone area then underground tanks might be your best bet.

Every manufacturer of tanks may experience a failure.  It’s exactly why manufacturers offer a warranty, to ensure your product will be repaired or replaced should it fail.  Industry wide figures confirm the failure rate of polyethylene tanks is less than 1% of all tanks sold in 2005. Your local consumer organisation will also be able to provide verified information about complaints made in relation to tank failures of all kinds, not just poly. Members of Association of Rotational Moulders Australasia (ARMA) agree to abide by a Code of Conduct and ARMA is available to help consumers reach an agreement with any manufacturer who is a member of the organization.

No matter what you read, every material used to make water tanks has an expected life span that will be affected by its manufacture, quality, and exposure to the environment.  Unlike steel and concrete tanks, polyethylene tanks are subject to UV degradation.  Special additives are included in the plastic during the manufacturing process to help to extend its life by protecting it from UV degradation. The UV rating shown for the material used to make a tank, refers to a standard test that gives a measurement of the plastics resistance to sunlight. Poly tanks which have been in service, in very harsh environments for long periods of time may contain no more UV stabilizers but continue to hold water for many more years. There are minimum requirements for how long the UV has been tested to, but double the UV rating, does not mean the tank will last twice as long.

There are existing studies regarding the leaching of substances from PET into water (like clear plastic water bottles you buy everywhere), however these are inconclusive and a completely different material to that used in poly tanks. Plastic tank materials are made to meet strict guidelines for potability (safe water storage) and food contact.
Steel tanks made from galvanised steel may leach excess concentrations of zinc into the water and this can alter its taste.  It's important to note that this is not a health risk.

Concrete tanks may leach minerals such as calcium into the water.  This is similarly not considered a health risk.  New tanks may impart lime and should be flushed before first use.

While most people who live on farms in Australia drink rainwater that has been caught and stored in tanks many local authorities have rules about drinking water in urban areas.

It’s also important to remember that while many Australians were raised on tank water, they have had an opportunity to develop immunities to organisms that it contains that your urban family may not have. Governments recommend water tanks in urban areas for use outside the home and for use in areas of the house where it’s not used for drinking.  Depending on your particular circumstances, you should always install a first flush type device, even if you don’t intend to drink the water.  For more information on first flush systems and other tank additions, please click here.

No matter what you may have been told, water stored in poly tanks or tanks with plastic lining should have no taste.

Of course, this depends on the maintenance of your roof, gutters and the tank itself. You should be aware however, that most rainwater tanks are not approved for drinking water by the local authorities in cities.  This policy is not based on any "fears" about any of the materials used to manufacture tanks and relates back to the possibility of unclean drinking water from poorly maintained roofs and other contaminants that may enter the tank.

Steel tanks made from galvanised steel may leach excess concentrations of zinc into the water and this can alter its taste.  It's important to note that this is not a health risk.

New concrete water tanks may leach lime thereby increasing the pH of water.  This can also alter the taste.  Concrete water tanks may need to be flushed before first use.  Many find the taste of water from concrete tanks to be superior due to calcium and other minerals imparted by the concrete walls. 

If you have a plastic or steel tank, they can be completely recycled.

Polyethylene is already regularly recycled and used again in different products. The poly tank industry has shown a real concern for our environmental future by working with Auckland University on finding new ways to make it easy for tank owners to recycle their own tanks at the end of their product life.

Steel tanks can be similarly recycled.  In fact, steel is one of the world's most recycled materials as it can be easily melted down and transformed into new products from cars to paper clips.