FAQs

What is the difference between steel and plastic water tanks?

There are a number of important differences between steel and plastic (polyethylene) water tanks:

• Steel water tanks are 100% UV-proof.  This means they will not degrade in sunlight. Plastic water tanks (polyethylene) are affected by Ultra Violet light and will break down over time.
• Steel water tanks can be made to almost any dimension. This means you can have a water tank for your home that fits perfectly in any available space, maximizing the amount of rainwater you can harvest.  Plastic water tanks can only be made in a small range of sizes.
• The strength of steel water tanks means they will not bulge or stretch when full of water. As a result, the slimline range of steel water tanks take up considerably less space on your property than plastic tanks.
• Steel is the most environmentally friendly material from which to make water tanks. Not only are they fully recyclable but the environmental impact of steel water tank production is less than that of tanks made from any other material.
• Steel water tanks offer a much more attractive alternative to plastic. The iconic steel water tank is often specified by architects to provide a design element to new homes and renovations. They are also available in a range of Colorbond colours. 

What size water tank should I install?

The general rule is to install the largest tank possible as the bigger the tank, the less it costs you per litre of water harvested.  However, the optimum size of a water tank will be determined by a number of factors:

• The available space on your property.  This includes any restrictions with access to the site like fences, retaining walls, trees, air conditioning units etc. 
• The intended use of the harvested rainwater. When used as a complementary water source (where the property is also serviced by mains water) it is important to consider the intended use of the harvested rainwater.   A lot more water is required for watering lawns and gardens and topping up pools than for flushing toilets and filling up washing machines (see “Cycle of Usage” notes below).
• The size of the catchment area.  This refers to the total roof space that will be used to catch the rainwater.  As roofs are generally comprised of sections, the catchment area is determined by the sections of the roof that services the downpipes that are directed to the water tank.  The larger the catchment area the smaller the water tank that is required, as it will fill more often. 

Cycle of Usage
This refers to how often the harvested water in a rainwater tank is used and replenished by rain events.  The most efficient use of rainwater, from a conservation perspective, is to use it as a complementary water source for flushing toilets and filling up washing machines.  This can account for a large portion of the water used inside your house.  By using the rainwater in this way your water tank is constantly being depleted then topped up each time it rains.  If rainwater is not used frequently it will just overflow to the storm water drain at each rain event.

How much water can I catch?

The size of the catchment area will determine the amount of rainwater harvested with each rain event.  One mm of rain will harvest one litre of rainwater for every one square meter of catchment area (roof space).   For example, if you have a catchment area of 50 square meters, you will catch 500 liters of rainwater whenever you receive 10mm of rain.  (Keep in mind we generally experience about 10-20% loss, so it might actually be about 400L per 10mm of rain).

Where is the best place to put a water tank?

Again, this is determined by a number of factors:

• The slope of the site. The most appropriate site will be on level ground, away from retaining walls. Extra installation expense may be incurred if your site needs to be excavated to make a level foundation.
• The downpipe location.  You should aim to connect as many downpipes to feed your tank as is practical. The closer the water tank is to your downpipes, the more efficient the water harvesting system will be. If downpipes need to be diverted and run horizontally over long distances then the installation expense will increase and the efficiency of the system may be compromised.
• Aesthetics.  While a well positioned water tank can add a design element to your home, most people are not likely to install a water tank where it is highly visible. This is an important consideration.
• Proximity to laundry or toilets. Where a water tanks is used to feed a toilet or washing machine it must be installed by licensed plumber. Again, the shorter the run of pipe work from the tank site to the internal appliance, the less expense will be incurred in installation.

What does the water tank need to sit on?

The most appropriate base for a water tank is a concrete slab.  Ideally this would be a minimum of 100mmin depth and 100mm larger than the width and length (or diameter) of the water tank.  Reinforcing steel mesh should be used in the slab.

Another method of constructing a base is with pre-cast concrete slabs on a bed of crusher dust.  It is a good idea to seal the crusher dust in with concrete pointing or treated pine railings so it doesn’t wash away.

Compacted crusher dust bases can be used for round water tanks. The crusher dust should be retained to prevent erosion.  Over time, it may be necessary to augment a crusher dust base.

You can find more detail about tank base preparation here.

Can I drink the water from my water tank?

Wherever there is a town supply of mains water it is not recommended that you drink the water from your tank. Tankworks water tanks are made from a food grade AS4020 certified material, so they can be used for storage of potable water. There are filtration devices available that can help to ensure that your tank water safer for drinking. Please Ask an Expert if you have more specific questions about water filtration.