Underground
Underground Tanks

Waterplex’s Affordable and Reliable Underground Water Tanks

Underground rainwater tanks are the perfect solution for limited space applications, or when you want to hide your rainwater storage. They can be as durable as steel rainwater tanks and carry just as much water without occupying any visible space.

Get Low Profile Underground Water Tanks for Your Home

You should consider an underground tank for rainwater storage if:

  • you have limited space available for your water tank
  • you want to hide your rainwater tank
  • you are looking for a "central storage" area that will allow you to harvest rainwater from the whole of your roof

Waterplex polyethylene underground water tanks can be used for:

  • rainwater storage for irrigation or reticulation back into the home in line with local, state and federal requirements or guidelines
  • detention of rainwater to meet local council building requirements
  • retention of water to meet local council requirements

Harvest and store water effectively with an Underground Rainwater Tank

For easier, cheaper and faster installation you should choose the lowest profile underground tank that suits your application.

If you have any questions about the selection or installation of an underground rainwater tank, call the team at Waterplex on 1300 72 66 70.

Lowest Profile
Donut 3,000 lt
Bagel 5,000 lt
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Graf Carat Tanks
Filtration and Drainage Cells

How you choose the best underground tank for you

  • Measure the available width and length of the area where it is to be installed (assume that a width of 2m x 5m is available in your back yard).
  • Divide the available area into the required capacity to get the optimal low profile underground tank height in millimetres. Assume the required capacity is 10,000 litres. The area is 10m² (2m x 5m). So for a capacity of 10,000 litres, divide the capacity by the area (10m²) = 1,000mm (or 1m) required depth.
  • If the tank is generally accessible, a lockable lid should be installed Check with the manufacturer to ensure a lockable lid option is available.
  • If the tank is to be installed in a trafficable area, the collar and lid of the tank should be certified to be load bearing. Check with the manufacturer to ensure that the an option for a load bearing lid and supporting collar is available.
  • Choose the underground tank that most closely meets the above criteria.

The most important criteria in selecting the right underground tank

  • Ensure that the manufacturer is a company that is accredited to the Australian Standard for Poly Water Tanks (AS4766).
  • Ensure that the tank is compliant with the Australian standard for septic tanks (AS1546.1). This is critical to ensure that an underground tank can withstand the weight and forces associated with being buried.
  • Where possible, ensure you install the lowest profile underground tank to minimise the cost of excavation:
  • An excavation deeper than 1500mm (1.5m) must be fenced or the sides of the excavation must be "shored up" (Worksafe’s Working at Depth Guidelines (Mines Act - Trenching) 1982).
  • If the underground tank will be generally accessible once installed, ensure that the option of a lockable lid is available for obvious safety reasons. If it will be installed under a load bearing area, ensure that the option of a lockable load-bearing lid is available.
  • Underground tanks should always be accessible for any on-going maintenance. The man hole should be large enough to install and remove submersible pumps and to remove sediment from time to time. Waterplex recommends a minimum manhole access of 300mm.

Using an underground rainwater tank as a retention tank or detention tank

The interconnection foot on each of the tanks is also the foundation of a retention / detention system. By drilling a hole to match the council-specified discharge rate (i.e. orifice plate) in the interconnection foot and positioning the overflow pipe at the desired storage level, an effective 100mm retention / detention system can be created.

If you have any questions about the selection or installation of an underground tank, or want to enquire about our flexitanks and other products, call the team at Waterplex on 1300 72 66 70.

Underground tanks from Waterplex can be used to store water in the capacities below by combining multiple tanks. For larger storage requirements, contact the team at Waterplex on 1300 72 60 70:

Underground Water Tank Capacity Configuration

Total Capacity Tank Configuration
3,000 litres 1 x 3,000 lt donut
5,000 litres 1 x 5,000 lt bagel
6,000 litres 2 x 3,000 lt donuts
8,000 litres

1 x 3,000 lt donut

1 x 5,000 lt bagel

9,000 litres 3 x 3,000 lt donuts
10,000 litres 2 x 5,000 lt bagels
11,000 litres

2 x 3,000 lt donuts

1 x 5,000 lt bagel

12,000 litres 4 x 3,000 lt donuts
13,000 litres

1 x 3,000 lt donut

2 x 5,000 lt bagels

15,000 litres 3 x 5,000 lt bagels
16,000 litres

2 x 3,000 lt donuts

2 x 5,000 lt bagels

18,000 litres

1 x 3,000 lt donut

3 x 5,000 lt bagels

19,000 litres

3 x 3,000 lt donuts

2 x 5,000 lt bagels

20,000 litres 4 x 5,000 lt bagels
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Why Waterplex

The Waterplex Group are specialists in producing innovative solutions for storing & harvesting water without taking up all of your valuable space around the home. Waterplex are a leading provider of water tanks in Australia and we have been part of the Australian water industry for over 10 years. We have built up a reliable national network of resellers and highly experienced installers that deliver a "supply and install" solution that is second to none.

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