Buying A Tank

Plastic, or polyethylene, water tanks are now the biggest selling sector of the booming water tank market.  This page includes a range of information to help you make the right decision on a tank to meet your own personal needs.  Buying a water tank might seem like a daunting task, but it is as easy as 1, 2, 3!

 

1. Deciding how you plan to use the water

When it comes to harvesting rainwater, the first thing you need to consider is how you plan to use the water you save.  Many tank owners use their tanks to combat water restrictions and to reduce water usage costs, allowing for a lush, green garden all year-round.  Rainwater may also be redirected back into the house for use in the kitchen, bathroom, and laundry.  The more uses you plan for your water will help you determine the size of the tank you will need.  Government guidelines differ between local authorities and some will have specific rules about whether tank water can be used in the entire house, only for washing and toilets, or only for the garden.

 

2. Calculating how much water you are capable of capturing

Weather patterns vary, so it’s a good idea to store as much water as possible, in case it’s a long time between rainy days.  Take a look at the rainfall in your area by checking out your local weather website.  Many tank suppliers can help provide you with this information too. You will need to know the approximate measurements of your roof available for channelling the water into your tank.  Additionally, the more downpipes you have, the more water you will be able to capture when it rains.  As a general rule, 1mm of rain over 1 square metre of roof area will result in 1 metre of rainwater entering your tank.

There are many things you can do to ensure the best quality water flows into your tank.  It is important to find out if your roofing material or the paint used on your roof or in your gutters etc., could contaminate rainwater.  For example, tar-based coatings can bind other harmful organic chemicals to the roof or gutter and can be difficult to clean. Rainwater should not be collected from parts of the roof that incorporate a chimney from a wood burner, discharge pipes from roof mounted appliances such as evaporative air conditioners or hot water systems, chemically treated timbers; or lead-based paints or flashings.  First Flush Systems and leaf guards can also prevent unwanted contaminants from entering your water tank.  Click here to find out more about additional tank fittings.

 

3. Choosing your tank

Finally, you will need to decide which type best suits your space.  Above ground, cylindrical tanks are the most common and come in straight wall or corrugated sides.  There are various models available, including those that will fit under the eaves of your house or those that can be used as fences or walls in your outdoor areas.  If space is an issue for you, there are a range of slimline tanks available.  These tanks are usually ovular or rectangular and are best suited to homes where outdoor space is highly valued.  Alternatively, underground tanks are a great option if space is limited.  If you value esthetics highly, then poly tanks may well be your first choice as they have clean, smooth lines and come in a huge range of colours and styles including modern straight wall designs or the more traditional corrugated styles.  

10 TIPS FOR BUYING A TANK

This section is designed to help you make an informed decision and choose the best tank for your needs, ensuring that it continues to do an effective job for many years to come.  It's also vital to know that a water tank is made of the right material for your family's health and local conditions.  Ask your agent or manufacturer if your poly tank meets Australian & New Zealand Standards - is it certified to AS/NZS 4766: 2020 Polyethylene Storage Tanks for Water & Chemicals? They will be able to show you a copy of their certificate or the tank will be clearly marked as being licensed to the standard.  

The standard isn't mandatory, or necessarily applicable depending on your tank. Here are some great questions to ask when buying a tank to ensure you're getting a quality product:

Where was the tank made? 

Some imported tanks are made from material that isn't suitable, might not have a warranty, or include fittings that are difficult and expensive to replace.

Is the plastic used in the tank certified as safe for drinking (potable) water? 

Whether it's just the lining or the entire tank, properly certified polyethylene is safe for drinking water. Unfortunately, some imported tanks may not be made from material which has been properly tested.  It is important to note that some councils do not allow tank water to be used for drinking.

Does the manufacturer maintain a product trace system? 

Good manufacturers will be able to trace your product to its source materials and will hold records of when and where it was made.  They will also be able to provide details of the tests it underwent before leaving the factory.

Does the tank have a warranty? 

Don't be seduced by lengthy extended warranties. Ten years is a very reasonable warranty period for plastic tanks.  Steel and concrete tanks typically have longer warranty periods. Carefully read the conditions and installation instructions before you buy so that you know your rights and obligations should you ever need to make a claim.

Has the tank design been tested? 

Like any material, plastic has some limitations when it is placed under stress (by filling). It's important that your tank has been well-designed and properly tested to ensure its suitability for purpose.  Although steel and concrete are stronger materials, it is still important to make sure the design is suitable.

Is the stated capacity of the tank calculated according to the standard? 

The calculation in the standards ensures that manufacturers can only state the actual amount of water that can be stored in the tank once fittings have been installed.

How should I maintain my tank and installation to ensure my warranty remains valid? 

Your manufacturer should provide you with written guidelines to help you maintain the base fittings and installation of your tank so it will last and continue to provide excellent quality water storage.

Has the thickness and colour of the plastic been calculated according to the standard? 

The Standard sets strict guidelines concerning the thickness and colour of the material to prevent light entering the tank as this can lead to algae growth.

Does the plastic contain UV protection specifically for our climate? 

Our local climate can be incredibly harsh.  Polyethylene is ideal because it contains UV-stabilising ingredients. 

Is the tank made by a member or supporter of the Association of Rotational Moulders? 

The Association of Rotational Moulders (ARMA) is a representative body of the majority of leading poly tank manufacturers in Australia, New Zealand and the Pacific region. We help our members to maintain their status at the forefront of the industry and to set the leading standards in the water tank marketplace.

FREQUENTLY ASKED QUESTIONS

Tank manufacturers want your business and, in an attempt to do so, some may advertise information about water tanks that can be confusing. We advocate that our members sell their products on their own merits and do not indulge in criticising other people’s products to sell their own. We’ve included lots of information in this section to help you understand the issues involved in providing home water storage.

Are Mosquitoes a problem?

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.

Do poly tanks cause cancer?

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.

Can my tank split at the seams?

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.

How long will my tank last?

There are tanks that have been giving loyal service storing liquids for over 30 years. 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.

What kind of problems can bushfires cause?

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.

Can my tank fail?

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. 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 the 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 organisation.

What does a UV rating mean?

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 plastic's resistance to sunlight. Poly tanks which have been in service in very harsh environments for long periods of time may contain no more UV stabilisers but will continue to hold water for many more years. There are minimum requirements for how long the UV has been tested for, but double the UV rating does not mean the tank will last twice as long.

Will my tank leach chemicals into the water?

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.

Is my tank water safe to drink?

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.  

Can you taste the tank material?

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 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. 

Can my tank be recycled?

If you have a plastic or steel tank, it 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.