thisplace.com.au - Rainwater Tanks

By using water from rainwater tanks, household demand on water from the reticulation system can be reduced. Even if tank water is unsuitable for drinking purposes, it can be used for watering the garden or filling the pool.

Is a Rainwater Tank right for you and your Water Needs?

Rainwater tanks have long been a source of domestic water in Australia. At one time, they were a standard feature of suburban backyards. They gradually disappeared as town and city water supply services expanded. Today rainwater tanks are necessary for many rural and outback homeowners.

Tanks are also being rediscovered by people in urban areas searching for ways to reduce water bills and play a part in protecting the environment.

Before buying a water tank, consider:

Local council regulations and restrictions.
State regulations related to mosquito control and eradication.
Reasons for wanting a rainwater tank.
The type and size of the system you need.
Water quality.
The cost of buying and installing a tank.
The financial benefits.

Choosing a Rainwater Tank

The size of the rainwater tank needed will depend on:

Rainfall in your area.
Roof area available.
How you plan to use rainwater.
The number of people living in the house.
Water Usage.

Types of Tanks

Galvanised

The most common type of tank is the galvanised steel variety, which is available in rust-resistant laminated linings such as Zincalume or Aquaplate. It is the most inexpensive but has a limited life span.

To reduce corrosion in these tanks, a dispenser of crystals of metaphosphates is sometimes used prior to initial filling. New galvanised tanks are now available with food grade polymer lining to prevent corrosion. When cleaning older tanks it is important not to disturb the film which builds up in the inside walls of the tank, as this helps protect against corrosion.

Polyethylene

Polyethylene tanks are usually fully moulded from food grade polyethylene and are easily transported. The water held in food grade polyethylene tanks is not contaminated from the tank in any way. Being non corrosive, the tanks do not require a concrete slab to sit on and any number on inlets and outlets can be easily installed. Properly moulded tanks have a long life span.

Fibreglass

Fibreglass tanks, although more expensive, are long lasting because they resist corrosion and are not affected by chemicals or moisture.

Fibreglass tanks allow more light entry than other types of tanks, which encourages algal growth. To prevent this, tanks should be sealed with a black covering inside or painted on the outside. Some tanks are manufactured with sufficient pigment to prevent this problem occurring.

Concrete

Concrete and ferro-concrete tanks are strong and long lasting and can be installed underground. Larger tanks often have to be cast in-situ. New concrete and ferro-concrete tanks will need to be adequately flushed to remove the concrete taste from the water.

Modular

Modular tanks are rectangular in shape rather than round, and are made from galvanised sheet steel with a heavy coating. Sizes are limited as they are designed to fit under the eaves of a house.

Expenses $$$$$

The purchase price of a rainwater tank is not the only expense. Other costs to be considered are:

Transportation
Installation
Alterations to gutters and downpipes
Tank stand or foundation work
Additional plumbing
A first flush rainwater diverter
A cleaning device to filter the water collected from the roof
A pump where necessary

Installation

Installation of the downpipe should ensure no water or rubbish can remain in it between rain periods.

Water Quality

Water quality in tanks can be affected by many things:

Atmospheric pollution
Bird and possum droppings
Roofing materials and paints
Trapped insects and small animals
Rotten leaves
Dust on roof
Installation

Note: Tank water doesn't always meet microbiological guidelines for safe drinking quality water.

Tank Maintenance

Tanks are designed to filter leaf litter and prevent entry by insects and small creatures like lizards. All tanks need regular maintenance to work properly. Tank maintenance is the key to water quality, it is important to:

Keep gutters and roof clear of leaves and other material. More frequent checks are needed if there are overhanging trees.
Clean inlet strainers whenever necessary, or use self cleaning strainers.
Check for sludge every few years to remove the mud, which comes from dust settling on the tank floor.
Make sure the inlet strainers, mosquito proofing and lids are in good repair. Lids should be tight fitting.

Roofing Materials, Paints and Environmental Aspects

There are some circumstance where rainwater should not be collected or where special precautions should be taken to ensure good water quality.

Tanks should not be used to collect water from roofing where lead based paints or tar based coatings have been used.
Run-off collected from roofs with lead sources (eg flashing) or through some types of PVC pipes may contain lead.
New roofs made of fibrous cement will leach lime for a while, so any rainwater should be discarded for an entire season.
Roofs painted with acrylic paints will have dissolved detergents and chemicals in the first few run-offs, which should be discarded.
Run-off collected in some urban and industrial areas will contain pollutants and may not be suitable for drinking water.
Run-off collected in some agricultural areas may be contaminated with agricultural pesticides and residues, and may not be suitable for drinking water.

When you use a tank you have to maintain a constant vigilance in monitoring water quality. Rainwater tanks offer homeowners the chance to reduce water usage and to protect our environment for the future.

Source: WaterWise Rainwater Tanks FH6 brochure