Installations

STEP 1: SELECT AN APPROPRIATE SITE

Selecting the most appropriate site for your water tank will be based on a number of factors. 

Access to Site
The available access to a proposed site will often limit the size of the tank or the location of the site itself.  Plenty of people have room for a 10,000 litre tank in their backyard but cannot get the tank there because of side boundaries or structures such as garages or pergolas. In such cases it might be necessary to consider the front of the property. 

Catchment Size
The catchment size is the area of roof that services the tank.  In most cases only a proportion of the roof will suffice as the catchment.  An area of 50 square metres will usually have one to two downpipes that allow the water to escape from the gutters.  This sized catchment will catch 500 litres for every 10mm of rain and is often enough to service a tank up to 10,000 litres.

Internal Appliance Location
To keep the internal plumbing costs to a minimum it’s a good idea to place the tank as close as possible to the toilet or laundry if the tank is to be plumbed internally.

Council Boundary Restrictions
Many local councils have boundary restrictions that determine where a tank cannot be placed.  The Brisbane City Council, for example, requires you to apply for a relaxation of the boundary restriction if you wish to place a tank within 6metres of the front boundary when a tank is to be placed at the front of the property.

STEP 2: PREPARE THE SITE
A water tank needs to sit absolutely level when properly installed.  This means the proposed site might need a little work.  It is always better to excavate to level rather than build up with road base or crusher dust.  This will ensure the tank won’t lean when it is full of water.  Where a lot of excavation is needed the site might also need some retaining so the excavated earth won’t collapse onto the base. 
 
Site preparation can be time consuming and expensive.  If you’re feeling fit enough you can dramatically reduce the cost of installation by doing it yourself.

STEP 3: CONSTRUCT THE BASE

Concrete Slab
The no compromise solution to base construction is a reinforced 100mm concrete slab.  A slab can be square or round.  The base should always be 100mm larger than the diameter of the tank.

Crusher Dust
In many cases a retained, compacted crusher dust base may be all that’s needed.  You can use 100mm treated pine railings, screwed together at the ends to retain the crusher dust but many other materials are appropriate.  The crusher dust should be anywhere from 50mm to 100mm high.    

A crusher dust base is considerably cheaper than a concrete slab, but may need to be augmented over time.  Heavy rainfalls can erode a crusher dust base and may cost you extra if it needs to be repaired. 

Crusher dust is available from any landscape material suppliers.
 
Pre Cast Concrete Slabs
A series of pre-cast concrete slabs on a sealed bed of crusher dust is an appropriate base for a Slimline tank.  A 3,000 litre tank measuring 2550mm in length and 850mm in depth can be placed on five (5) pre-cast slabs that measure 900mm x 600mm x 40mm.

STEP 4: PLUMB FROM THE GUTTERING

Down-Pipe Location
For best results the down-pipes to be diverted to the water tank should be no more than five (5) metres from the tank site.  The ideal fall should be approximately 300mm from the top of the inlet pipe to the top of the tank.  Ideally you want to position a tank as close as possible to the house to avoid overhead pipes.  Overhead pipes need to be supported every 2m so they don’t bow when full of water. 

Wet Systems
A wet system is such where the inlet pipe runs from the house to the tank via an underground trench.  The water will find its way to the tank as long as the inlet height of the tank is below the height of the gutters.  A siphon effect will ‘pull’ the water through as it finds its own level.  It is called a wet system as there is always water in the pipes up to the height of the tank.  Wet system lines need to be flushed out regularly to keep the water clean.
Wet systems are particularly useful when the water tank is situated some distance from the house.  Many rural properties with large tanks have wet systems that harvest the water from the entire roof.

Overflow
All installations need to give some consideration to the water tank overflowing.  In fact most councils insist the overflow be piped back to the existing stormwater or a rubble pit.

Ideally the overflow will be piped back to the existing stormwater system.  If there is no existing stormwater system, or the size or position of the tank precludes the overflow returning to the stormwater, a rubble pit may be required.  A rubble pit is a cubic metre excavated from the ground and filled with drainage gravel.  The overflow pipe will be directed to the rubble pit.

STEP 5: CONNECT THE PUMP

In most cases you will need a pump to get the water out of the tank.  Ideally the pump will be located as close as possible to the tank and on the same level as the base and will either sit on its own concrete slab or mounted to the tanks concrete slab.  A pump is usually plumbed to a tank via a 25mm non-return valve and a small length of 25mm suction hose. A length of 25mm poly pipe then extends from the pump to a mounted garden tap.  This is a standard pump installation.  Pumps can also be connected to irrigation systems and internal appliances such as toilets and washing machines.  A licensed plumber is always required to plumb to an internal appliance.  

While pumps are made to handle all weather it is a good idea to keep the pump covered. Pump covers are available in a range of colours and materials.