If you're like me and live in a townhouse or a unit, you probably assume you don't have the space for a water tank. Not so! There's plenty of space saving water tank option on the market. Stroll into your local Bunnings hardware and take a look around, there's plenty of options to choose from at relatively affordable prices including these slimline rainwater tanks.

There are rainwater tanks of all shapes and sizes to fit in a small court yard. The Waterwall, for example, can fit across a back fence or sideway, while the Rain Reviva make a water bladder that fits under your house.

Water tank experts have expressed concerns over the safety of some water tank instillations. Experts are suggesting that if rainwater tanks have not been installed on a solid base, the footing may become unstable causing safety issues around homes.  They have also suggested that plastics used in imported tanks may degrade quickly in harsh Australian conditions.  Full report in the Sunday Mail.

Tankmasta has a great little rainwater calculator to help you calculate how much water could be collected from your roof into a rainwater tank annually. I was out in an industrialized area near Melbourne recently and I was amazed at the about of roof area some factories had with no sight of a rainwater tank.

Some of these factory roofs would literally cover hectares. Tankmasta's raineater calculator suggests that a 1 hectare (1o,000 sq meters) roof in Melbourne would collect 5,877,000 litres of water annually. That's not to be sneezed at!

You can find the rain water calculator at the bottom of Tankmaster's home page.

The ABC reports that Hill Industries, the people that make Hills Hoist, has just turned over $1b in revenue. No doubt due to the good old Australian company's water tank division called Team Poly.  Team Poly manufacture a huge range of polyethylene water tanks in all shapes and sizes.  Included in their water tank range are:

• Corrugated Water Tanks
• Drink Water Tanks
• Modular Water Tanks
• Slimlie Water Tanks
• Septic Tanks

You can check out the range at the Team Poly website.

Taking environmentally friendly to a new level, the VersiTank rainwater tank from Elmich is made from recycled plastics and manufactured in Australia.  The VersiTank storm water tanks store run-off from roofs and are suitable for domestic rainwater storage and commercial developments.

Lightweight, high strength interlocking panels clip together to make up the water tank assembly, assembled on site.

You can find out more at the Elmich VersiTank product page.

The Brisbane Times reports that the residents in Brisbane will have to ensure their rainwater tank is plumbed into their laundry and toilet to be eligible to receive the $850 water tank rebate.

"Lord Mayor Campbell Newman said the change was needed because the rebate program would not conserve the city's water supplies unless people started using rainwater inside their homes."

Brisbane has been struggling to keep water consumption down to 140 L per person and although this change to the rebate rules may hurt the hip pocket, it will go a long way to helping Brisbane reach the consumption target.

Rain water tanks come in all shapes and sizes and materials. So what material should your water tanks be made from?

This all depends on your budget and whether the tank is above or below ground. Currently Polyethylene tanks are the most cost effective, but you may wish to consider other materials.

Polyethylene rainwater tanks are light, durable, easy to transport and come in a wide range of colours. They can be used above or below ground, however they generally don’t last as long as a concrete tank.

Fibreglass water tanks tend to be more resistant to rust and chemical corrosion and generally best suited to above ground instillations.

Concrete rain water tanks are long lasting, durable and can be built above or below ground. Above ground, concrete has the advantage of keeping water cooler and reducing algal growth.

Metal rain water tanks, like polyethylene, are light, durable and easy to transport. Bluescope Steel offer a great rang of metal tanks.

You can buy a huge range of rainwater tanks through ebay.

How much should you expect to pay for a rainwater tank? The old adage regarding a piece of string comes to mind for the answer to this question. Here are four main factors which will contribute to the cost of your water tank:

• Water tank size
• Instillation requirements
• What material the water tank is made of
• Delivery

You can purchase a 1000 Litre tank for as little as $300, or for something smaller, Australian Waste Management sell wheelie bins, 120 Litres from $65. Now a days you can order rain water tanks in all shapes and sizes (and costs) but you can pick up a larger tank of 5,000 Litres for as little as $1500. Need something a little larger? A 100,000 Litre tank will cost you around $8000.

Add to this the cost of tank instillation and plumbing by a registered plumber which will vary depending on whether or not you’re going to use your tank water for the toilet and laundry. Typically, a small above ground tank will cost you around $300 to install plus the cost of a pump – starting at around $200.

Check out rainwater tanks for sale through ebay.

No space for a whapping big rainwater tank in the back yard but keen as mustard to harvest the rainwater from your roof run off?  Than check out the eco sac.  The eco sac is like a large flexible water bladder that fits under your house.  Water stored in the eco sac is suitable for safely fill swimming pools and fish ponds without fear of contamination from the bladder.  Eco sac configurations can store from 2,600 litres up to 50,000 litres and qualifies for government rebates where they apply.

Check out the Eco Sac website for details.

If you’re wanting to “get off the grid” altogether and not rely on mains water for any of your water needs then you’ll need a 50,000 – 100,000 litre rain water tank. However, it’s not recommended that you use rainwater for drinking in built up suburban areas.

If you’re aiming to keep your garden green all year round then you’ll need a 2000 to 4000 litre rain water tank depending on the size or your garden. You’ll also need a pump fitted to your water tank if you’re using a sprinkler system.

The toilet and laundry consume the greatest amount of water in the home, so if you’re plumbing a rainwater tank into these areas, you’ll want to go for a larger tank.

You can find cheap rainwater tanks through our Water Tanks ebay listings page . Just remember, in most cases you'll have to pickup the water tank or pay for delivery so buy a tank from a local distributor.