UNDERGROUND WATER TANKS
Do you want to harvest rainwater but don’t have space for an above-ground water tank? Our Li-Lo flat water tanks are the perfect solution for water storage under your lawn, garden or driveway.
High quality water tanks, hidden below-ground.
Li-Lo flat underground rainwater tanks have been developed specifically for efficient underground rainwater harvesting. Li-Lo’s German engineered and patented low-profile design requires minimal excavation making installation quick and easy. Available in 1,500 L, 3 000 L and 5 000 L capacities, and backed by a 10-year warranty, Li-Lo water tanks free up space above while safeguarding rainwater below ground.
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Save rainwater and space with Li-Lo underground water tanks.
GERMAN ENGINEERED
GRAF have been developing innovative high quality water tanks for over 40 years.
LESS DIGGING
Low profile requires significantly less excavation than a cylindrical tank, resulting in faster and cheaper installation.
SELF-ANCHORING
Patented design eliminates the need for ground anchors.
EASY FILTRATION
Integrated filter technology allows water to be filtered directly in the tank without the need for a separate filter shaft.
QUICK CONNECTION
Tanks and shafts have pre-fitted sealings. Telescopic dome shaft enables immediate installation.
SIMPLE INSTALLATION
Tanks are lightweight and easy to transport. Installation is fast and simple to do without tools.
VERSATILE COVERS
Plastic covers for pedestrian areas and steel for vehicle loading if tank is installed under a driveway.
100 % RECYCLABLE
Li-Lo water tanks are fully recyclable and made in state-of-the-art facilities to minimise environmental impact.
Nationwide delivery
Talk to us to get the water tank you need, delivered when and where you want it.
Underground water tanks FAQs
Why should I choose a GARANTIA underground rainwater tank?
GARANTIA is the home-and-garden brand of Otto Graf GmbH—the German engineering company behind the world-renowned GRAF rainwater-harvesting systems. GRAF have been developing and producing plastic water tanks and containers in Germany for more than 50 years. They have amassed vast experience and expertise while developing innovative products of the highest quality over this time.
We are proud to be offering GARANTIA underground water tanks for the first time in New Zealand. There are many benefits that make these underground water tanks an excellent choice, including:
- Completely recyclable polyethylene construction.
- Maximum stability due to heavy ribbing.
- Very long service life. 10-year warranty on materials.
- Stringent quality assurance checking in the Perth factory.
- Excellent water hygiene thanks to smooth interior surfaces and use of food-safe materials (DVGW tested)
- Easy to transport and install due to low weight
- Easy and safe to install due to ready-to-plug connections
What do I need to consider before excavating?
To ensure sufficient working space, the base area of the excavation pit must exceed the tank dimensions by more than 500 mm on each side, and the distance to fixed structures must be at least 1000 mm.
Contact our team for specific dimensions and to find out which configuration best suits your property. We’ll discuss your requirements and recommend the most suitable 1,000-litre water tank option.
Can I install a Li-Lo water tank under a driveway?
Yes, the Li-Lo rainwater underground tank with the cast iron cover (Class B) and cement support ring are suitable for installation in light traffic areas (max. total load 3.5 tonne). The tanks are not to be installed in areas where heavy goods vehicles are driven. The areas driven by light traffic must have a compacted earth covering of not less than 700 mm (27.6 inch) and a maximum of 1000 mm (39.4 inch). Under no circumstances is the load caused by vehicles to be transferred to the tank.
A detention water tank is primarily focussed on controlling the flow and release of stormwater to prevent flooding and erosion. Detention tanks temporarily hold and slowly release stormwater into the drainage system at a controlled rate. This helps manage peak flows during heavy rainfall, reducing the risk of downstream flooding and erosion.
Do Li-Lo underground tanks need to be anchored?
No – the patented ribbed base self-anchors, so concrete ballast isn’t required in normal soil.
Why do I need a dome shaft or dome shaft extension for my underground water tank?
A dome shaft (and its stackable extensions) lifts the opening of your underground water tank or filter up to ground level, giving you a frost-proof yet easy-to-reach access point for cleaning, inspection and pump servicing. Think of it as the tank’s “front door”. When your tank sits deep enough to stay clear of winter frosts, its lid ends up well below the surface. A dome shaft is the vertical collar that bridges that gap, so you’re not digging every time you need to pop the lid. A dome shaft (plus any extensions) makes underground tank access simple, safe and frost-proof—so you can keep your water system healthy without the hassle.
What happens when the underground water tank is full?
Underground water tanks must be fitted with an overflow (see instruction manual), through which the surplus water can either flow directly into the stormwater network or into the groundwater through percolation.
The simplest solution, though not the best from an ecological perspective, is for the water to flow into the stormwater network through an interface. When connecting your tank to the stormwater network, you must pay particular attention to the backpressure level. The overflow must be above the backpressure level. A backpressure flap should be installed if necessary.
How do I access the tank for cleaning?
The supplied double-walled PE lid opens to 600 mm allowing easy access.
Where do you deliver and how much does it cost?
We deliver tanks to metropolitan Auckland for free and can arrange nationwide delivery. Contact us to discuss your requirements and we will prepare an estimate.
Why should I choose a GARANTIA underground rainwater tank?
GARANTIA is the home-and-garden brand of Otto Graf GmbH—the German engineering company behind the world-renowned GRAF rainwater-harvesting systems. GRAF have been developing and producing plastic water tanks and containers in Germany for more than 50 years. They have amassed vast experience and expertise while developing innovative products of the highest quality over this time.
We are proud to be offering GARANTIA underground water tanks for the first time in New Zealand. There are many benefits that make these underground water tanks an excellent choice, including:
- Completely recyclable polyethylene construction.
- Maximum stability due to heavy ribbing.
- Very long service life. 10-year warranty on materials.
- Stringent quality assurance checking in the Perth factory.
- Excellent water hygiene thanks to smooth interior surfaces and use of food-safe materials (DVGW tested)
- Easy to transport and install due to low weight
- Easy and safe to install due to ready-to-plug connections
What do I need to consider before excavating?
To ensure sufficient working space, the base area of the excavation pit must exceed the tank dimensions by more than 500 mm on each side, and the distance to fixed structures must be at least 1000 mm.
Contact our team for specific dimensions and to find out which configuration best suits your property. We’ll discuss your requirements and recommend the most suitable 1,000-litre water tank option.
Can I install a Li-Lo water tank under a driveway?
Yes, the Li-Lo rainwater underground tank with the cast iron cover (Class B) and cement support ring are suitable for installation in light traffic areas (max. total load 3.5 tonne). The tanks are not to be installed in areas where heavy goods vehicles are driven. The areas driven by light traffic must have a compacted earth covering of not less than 700 mm (27.6 inch) and a maximum of 1000 mm (39.4 inch). Under no circumstances is the load caused by vehicles to be transferred to the tank.
A detention water tank is primarily focussed on controlling the flow and release of stormwater to prevent flooding and erosion. Detention tanks temporarily hold and slowly release stormwater into the drainage system at a controlled rate. This helps manage peak flows during heavy rainfall, reducing the risk of downstream flooding and erosion.
Do Li-Lo underground tanks need to be anchored?
No – the patented ribbed base self-anchors, so concrete ballast isn’t required in normal soil.
Why do I need a dome shaft or dome shaft extension for my underground water tank?
A dome shaft (and its stackable extensions) lifts the opening of your underground water tank or filter up to ground level, giving you a frost-proof yet easy-to-reach access point for cleaning, inspection and pump servicing. Think of it as the tank’s “front door”. When your tank sits deep enough to stay clear of winter frosts, its lid ends up well below the surface. A dome shaft is the vertical collar that bridges that gap, so you’re not digging every time you need to pop the lid. A dome shaft (plus any extensions) makes underground tank access simple, safe and frost-proof—so you can keep your water system healthy without the hassle.
What happens when the underground water tank is full?
Underground water tanks must be fitted with an overflow (see instruction manual), through which the surplus water can either flow directly into the stormwater network or into the groundwater through percolation.
The simplest solution, though not the best from an ecological perspective, is for the water to flow into the stormwater network through an interface. When connecting your tank to the stormwater network, you must pay particular attention to the backpressure level. The overflow must be above the backpressure level. A backpressure flap should be installed if necessary.
How do I access the tank for cleaning?
The supplied double-walled PE lid opens to 600 mm allowing easy access.
Where do you deliver and how much does it cost?
We deliver tanks to metropolitan Auckland for free and can arrange nationwide delivery. Contact us to discuss your requirements and we will prepare an estimate.
Contact us
Ready to make room for more water storage?
Tell us about your site and water capacity needs in the form or phone our team on 09 427 5281. We’ll confirm the best Li-Lo water tank solution to get your underground rain-harvesting sorted.