Last Updated Nov 23, 2010 · Written by Jaclyn Fitzgerald
A rainwater tank is a valuable addition to any property, saving you water and money as well as helping the environment. If you don’t want your tank to be visible or to take up your precious backyard space, you have the option of burying your plastic or concrete rainwater tank underground. Here’s what you need to know about the pros and cons of both of these types of underground rainwater tanks.
Plastic underground rainwater tanks are a type of rainwater tank that are designed to be installed underground while still operating effectively. These tanks are made from UV stabilised polyethylene (food grade) and are specifically designed and manufactured for strength, with factors such as large ribs added to the tank walls. Plastic underground rainwater tanks are available in sizes as small as 1000 litres right up to 10,000 litres. They are available in different shapes such as donut and bagel as well as traditional shapes.
The modern plastic rainwater tanks that are designed to be installed underground are extremely strong, so much so that they are even able to be positioned underneath driveways – allowing a car to be driven over the top of the tank. You can also plant a lawn or garden over the top of the tank (allowing clear space to give tank access of course), or position your entertaining area over it. Because they are shallow in depth, they don’t require as much excavation as concrete underground tanks and they can be installed and ready to use in a matter of hours by a plumber. If you need extra water storage, multiple units can be connected to each other.
Plastic underground water tanks are available with warranties of 7 years or more and comply with all relevant Australian Standards relating to water tanks. Some plastic underground tanks will require a concrete slab while others do not.
A concrete underground rainwater tank can be a valuable addition to your property, especially now that the newer construction techniques have made them lighter than ever before. To give them the maximum strength possible, they are reinforced with steel. You have two options with concrete underground rainwater tanks – to have them precast and delivered to your site where they can be installed straight away, or to have them poured on site to your specifications.
Concrete underground tanks can be more expensive to install than their plastic counterparts as more excavation is required but they are exceedingly durable and are at very little risk of “floating” (as some plastic tanks can). Concrete tanks are also at little risk of rusting, corroding, or damage from tree roots. If damage should occur, it can be easily repaired. As you have the choice between precast or custom poured tanks, you can choose the size of tank that suits your needs the best.
Because concrete water tanks are so strong, they are ideal for placing under driveways, courtyards, sheds, or other areas where they have to take heavy loads (to be safe, always make sure you find out the maximum load they can bear).