Precast Concrete Water Tanks – Absolute Concrete

Precast Concrete Water Tanks

A T5000 Fortress® tank from Absolute Concrete is New Zealand’s Toughest Water Tank and at 22500 litres actual storage (5000gallons) will satisfy all your water storage requirements.

While these tanks are commonly referred to as 25,000 litre tanks, no-one actually makes a precast tank that holds 25,000 litres, we prefer to be up front and honest about that.

Fortress® Tanks are the only tanks made with our special high tensile welded reinforcing mesh system that makes them intrinsically very, very strong.

Options are available for complete burial, vehicle surcharge, extra cover surcharge, anti-flotation bases, and because Fortress® Tanks don’t rely on the lid for side wall strength, they can even be used as plunge pools.


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Rainwater from your roof is the most common and best method of water collection in Northland.

In Northland a 120m2 roof should collect approximately 110,000 litres of water in a dry year.  For a four person household this equates to around 75 litres per day and the average usage is about 150 litres.  This sounds like a lot but we all know conserving water is important especially when you throw in a particularly dry Northland Summer!  Absolute Concrete Water tanks will meet your storage requirements.

Fortress® Tanks may be fully buried, completely out of sight so as not to disturb play areas or views.


      • The Fortress® Tank is a one piece round monolithic precast concrete tank.
      • This form of construction means no joins or weak points.
      • Reinforced with engineered high tensile welded steel mesh for maximum strength where its needed most.
      • 25% thicker in walls and base than our biggest competitor’s product.
      • 125mm thick base means you save on preparation costs for most install types.
      • Concrete tanks are designed to keep your water cool (up to 9° cooler than some alternatives)
      • Fortress® tanks keep the water in the dark that helps prevent algae growth.
      • Concrete water tanks are a reliable and convenient water storage in the event of fire.
      • Concrete water tanks do not require additional restraints in high wind zones.
      • An Absolute Concrete Fortress® Water Tank does not require a building consent.
      • Options for vehicle surcharge or additional cover surcharge.

Manufacturing standards

Absolute Pre-cast Fortress® Water Tanks are manufactured to standards NZS 3106 and use material that conform to NZS 3422 and NZS 3109:1997.  Fortress® Tanks are manufactured using high strength concrete and fabricated circular steel reinforcement (welded steel mesh) not fibre like some other manufacturers.  This gives us the ability to engineer more strength where it’s needed most and means that our steel is housed well within the concrete away from the elements, reducing the risk of rust in your water and creeping tank failure in years to come.
The T5000 Fortress® tank comes with a 125mm thick steel reinforced base so for installations where the lid is above ground, there is no need for compacted aggregate in your tank pad, just clean level ‘good ground’ along with 75-100mm of fines for bedding.
The tanks have ‘Swift-Lift’ lifting anchors cast into the concrete walls.

A range of tanks are available to suit your situation:

T5000 Fortress® water tanks may be completely buried and the standard lids are designed for pedestrian traffic only along with a up to 100mm of light free draining material such as bark, scoria or mulch. Tank lid sealing and manhole risers are optional depending on your style of installation so you’re not stuck with paying for something you don’t need.
Heavy Duty Tanks are available on request. Heavy Duty lids are designed to withstand pedestrian and up to 200mm of earth cover and we can also cater for tanks where light vehicle loads are needed.

For an engineered tank with maximum strength, no other tank comes close so make sure you specify a Fortress® T5000.

After installation of the water tank we advise that you make sure it has a load of water added to minimise any chance of flotation.

Siting Instructions for Water Tanks

Our tanks are delivered using our trucks each with a 15 tonne crane positioned at the back of the
deck. The site for the truck to park to offload must be level and allow for the truck to back up to the
tank site. The truck must then be able to put out the outrigger/stabilising legs to extend a total of 8.5 metres. The stabiliser legs can not be put onto fill, they must be supported by solid ground. The truck cannot unload off the side or on uneven ground. The crane is able to reach out approximately 2.5-5.0m from the rear of the truck depending on tank model and size and only
if these conditions have been met.

Please make sure:

      1. There are no overhead wires, branches, gate posts, etc blocking the access of the loaded Tank and Truck. The driver will take as much care as possible not to damage property but will not be held accountable for damage due to restricted access.
      2. The ground is firm enough for the truck. Make sure there are no holes, drains etc to fall into. If you have a wet site please have a digger or appropriate machinery on site.
      3. Siting requires a level site and a good foundation so that all the weight is distributed evenly on solid ground. The truck will not be stable on fill. Please ensure the digging material has been placed so that the truck can access the site.
      4. Crane legs must be able to be extended on flat level ground that is solid virgin country – not fill, preferably in accordance with NZS 3604.
      5. Each tank pad should be on level good ground with roughly 75mm of evenly spread uncompacted bedding fines such as Pap7. (Sand should only be used if it is captive or it will likely wash out and undermine the tank over time). If good ground cannot be achieved, a base of compacted aggregate will need to be installed before the bedding fines are added.

Please have your site prepared for our truck as we allow 30 minutes per tank on site. Please note:
Site preparation is the purchasers’ responsibility however we happy to carry out a site visit prior to
delivery to assist in your preparation. Any site work carried out by our company will be charged additionally.