Next level underground tank technology is here.
When your retention or detention tank has to fit underground, either very deep, in a shallow space, and/or for vehicles to drive over, APD’s StormLite3® has your ideal solution. Its unique modular rectangle system is extremely durable and watertight, using the same reliable 6mm polyethylene sheet that is used on our hazardous-rated chemical tanks. Installation has never been this easy, arriving on-site complete and ready-to-go. All you have to do is specify your requirements, then fill-in over the top of the highly durable delivered tank.
When you need underground stormwater detention or retention but are constrained by:
Our newest Tank Solution StormLite3® does it all with its unique APD design.
Designed to support loads up to 28 tonnes/sqm.
Solutions strong enough to support up to 2m of ground cover and/or withstand heavy traffic loads, so long as the overall 28 tonnes/sqm load limit is not exceeded.
As New Zealand’s leading plastic tank fabricators we know what it takes to make a robust tank shell.
We’ve combined our expertise and high quality materials to produce a 6mm thick shell that securely holds the modular tank elements together and is over 7x the thickness of the protective layer used by other modular systems. Every weld on every tank is leak tested during production.
So it can be installed quickly and safely, our StormLite3® tank is delivered complete with spigots for an inlet and vent pipe ready to connect to a manhole.
Tanks are supplied with lifting lugs, to simplify handling on site.
Fast installation saves costly additional man hours on site, keeping the time spent in the excavation site to a minimum; making for a safer and efficient work environment.
Minimum Tank Height: 458mm (1 Module)
Maximum Tank Height: 2150mm (5 Modules)
Maximum Buried Depth: 3m from base of tank
Maximum Cover Over Top of Tank: 2m
Maximum Tank Width: Approx. 4500mm (Requires Special Transport)
Maximum Tank Length is dependent on the height and width. Please contact APD for advice.
Minimum Cover to Finished Ground Level:
Non-Trafficable Install: 300mm
Driveway/Trafficable Install: 600mm
The StormLite3® tank must be connected to a manhole chamber as per the diagram, to limit silt intake into the tank and as a connection point for all inlets, overflow and orifice/outlet.
Modular tanks that fit any environment and give you the flexibility you need.
The internal structure of StormLite3® is composed of ProTank modules, arranged to utilise space effectively, fitting your volume requirements and site layout.
ProTank modules have a void space ratio of 0.95 and lock together vertically, up to 5 high, and pack together horizontally to form the shape of the tank.
Standard with all StormLite3® tanks are a tank connection spigot and a vent spigot for connection of the tank to a manhole chamber as shown in the illustration above.
Add on options are:
APD StormLite® Detention and Retention tanks can be installed under house or decks where space permits. Key requirements for this type of installation are for the tanks to not undermine any of the structural support of the building or for the tanks to be placed anywhere that a surcharge load can be applied to them by the building structure.
If the tanks are not to be completely buried then the minimum burial depth for the tanks is half the height of the cylindrical tank diameter. The tank shown in these images is a 1000mm diameter tank and it has been buried to a height of 500mm from the tank invert.
The Taupiri Development Project required that Storm water Detention Tanks be installed to detain storm water draining from the carpark area, prior to controlled discharge to the local stream. The Detention Tank design agreed on, was to have two underground Detention Tanks joined together to create a combined volume of 16.5 cubic metres (16,500 Litres) of storm water detention.
The StormLite® Storm water Detention Tanks were manufactured by APD as a matched pair, with built in 250mm outer diameter spigots to allow easy connection of the tanks during installation by Comins Plumbing & Gas Ltd. The Storm water Detention Tanks were each 10.8metres long and easily handled on site during installation, by a small digger.
To cope with the potential storm water flow, a 250mm outer diameter inlet spigot was added. Holes were pre-cut for overflow and outlet pipes and a pre-drilled orifice cap was supplied to minimise installation time on site. Contact APD during the design phase of your next project to discuss your requirements.
The Sunnynook Park Development project required the establishment of new toilet blocks adjacent to the carpark in Sunnynook Road, with rainwater being collected and then reused for flushing toilets in the new toilet block.
A 6150 Litre APD StormLite® storm water tank was selected and installed by Wiltek Maintenance Ltd to retain the storm water until required.
To meet site requirements, the Storm Water tank was manufactured by APD from polyethylene to the following dimensions: 1 metre diameter by 5.6 metres long. Weight: 350 kg.
The StormLite® Detention Tank was easily handled on site during installation by the A.J. Tutill & Sons Ltd HIAB truck. The tank was lowered into position using a single strop. Try doing that with a concrete tank of similar size. See our article concrete vs. plastic for more information.
Contact APD during the design phase of your next project to discuss your requirements.
There was no easy to use off-the-shelf tank that could meet the requirements for this site. QDC Works Limited needed to be able to detain 3,000L of storm water as part of their project but because of site restrictions they needed a tank less than 500mm high, buried 1.6m underground.
APD were approached to provide a cylindrical style StormLite© tank for this project but because of the depth of cover required and tight constraints on the tank height, this wouldn’t work.
We needed to deliver a tank inherently strong enough to withstand the load resulting from 1.6m depth of cover that was less than 500mm high. Like our other tanks it had to be optimised to contain the volume required while keeping the tank as small as possible; minimising the cost.
StormLite® with its modular design that can be easily scaled up or down to suit a residential or commercial site. Rectangular in shape to optimise water capacity in the space available the StormLite3 with its unique design can withstand the pressures of increased soil cover and/or heavy traffic loads. The tank was fabricated and available within 15 days.
What makes StormLite® stand out is that, unlike any other modular tank solution on the market, it is delivered to site pre-assembled and ready to go straight into the ground.
Modular systems are typically built on site and wrapped in layers of geofabrics and a membrane. APD Stormlite3 tanks have a 25 year design life and are pre-assembled undercover in our production facility regardless of the weather conditions to:
Everything was fabricated and delivered for QDC on time and on budget providing a solution with:
Meaning QDC received a practical, cost effective solution that they know they can rely on to drain storm water safely for years to come.
Make the affordable choice, with made to order economy.
Call APD now on (09) 263 7741.
StormLite® cylindrical tanks are made to order and delivery is normally within 3 – 5 days.
APD can supply PS1 documentation and project specific producer statements on request.
At around 250 kilograms, a 5000 litre StormLite® water tank is a mere fraction of the weight of concrete tanks. This means it can be moved around site with only a small digger. Designed strong, StormLite® can go under driveways, carparks, and grass. Tell us your volume requirement, and our make-to-order service will ensure your StormLite® tank adheres to Council regulations, while making your drainlayer’s job a breeze. Make the affordable choice, with made to order economy.
Our design keeps the tank outlet level with the tank invert, and tank overflow level with the crown, giving you maximum volume of the tank is used while still meeting council regulations.
The installation is very easy, tanks are supplied complete ready to install. A Silt Trap replaces the separate chamber that might otherwise be required and where storm water retention is called for, it doubles as a pump sump. See our Rain Harvesting Systems.
Volume is customised for your site – 1m3 to 30m3 (1,000 to 30,000 Litres) and each tank is made to order to the volume specified by council.
You don’t pay for, or install more tank than you require.
Available in 4 diameters – 645mm, 800mm, 1000mm and 1200mm.
Lengths are calculated to provide specific volumes and tanks are made from tough environmentally friendly polyethylene (PE). This material never rots or corrodes and is easy to handle. All fittings are supplied – including seals, outlet end cap to drill orifice in, and leaf trap/screen.
Where space and or fall are an issue we recommend StormSlim® above ground tanks or our StormSlab® in slab tank. Above ground Rectangular tanks are also available from APD for those projects where standard detention tanks just won’t work. Great for placing under houses and decks, these tanks can be custom made to fit between piles and structural supports. Tanks can be partly buried if required.
Baradene College Gymnasium
Client: Watts & Hughes Construction
System: StormLite® Underground Detention System
Total Capacity: 56,400 L
Project Overview
Watts & Hughes Construction partnered with APD to deliver a stormwater detention system for the new gymnasium at Baradene College.
The original design called for four joined StormLite® tanks (4 × 12,700 L) installed under a landscaped lawn area, providing a combined storage capacity of 50,800 L.
After the tanks were ordered, the project scope changed — the school decided to build a car park directly above the tank area.
This change introduced several structural and engineering challenges:
APD proposed an alternative configuration — three longer StormLite® tanks — which reduced the overall system width while maintaining structural integrity for the concrete slab above.
Two additional design adaptations were required:
Final configuration:
3 × 18,800 L StormLite® tanks (1,200 mm dia × 17 m long)
Total capacity: 56,400 L
Through careful redesign and collaboration with the engineering team, APD delivered a cost-efficient and structurally compliant solution.
The revised configuration enabled the car park construction to proceed safely above the installation — without increasing the project’s footprint or significantly impacting cost.
This project demonstrates APD’s ability to adapt designs quickly while maintaining compliance, performance, and client confidence.
“You have been exceptional to work with… extremely pragmatic, refreshing.
Simply put, for suppliers like yourself and APD — this is how you obtain repeat business.”
Understanding the role of retention tanks in smart water management.
As sustainable development becomes increasingly important, managing how water is collected, stored, and reused on-site is more than just good practice — it’s often a council requirement. One of the most effective ways to achieve this is by installing a retention tank. But when exactly is a retention tank the right solution?
Let’s explore the key scenarios where a retention tank is not just recommended – it’s essential.
A retention tank is an underground or above-ground water storage system designed to hold stormwater or rainwater for reuse. Unlike detention tanks, which slowly release water into the stormwater network, retention tanks store water permanently for non-potable uses such as irrigation, toilet flushing, or wash-down.
If your project involves rainwater harvesting for re-use in the home, garden, or commercial facility, a retention tank is ideal. It stores clean water that can be filtered and reused, reducing reliance on mains supply and lowering water bills.
Many local councils now include water reuse or retention targets in building consents for residential and commercial developments. Installing a retention tank helps meet these requirements and demonstrates commitment to sustainable water practices.
In areas where connection to public stormwater systems is limited or non-existent, retention tanks offer an on-site solution. By capturing water for later use or slow release, they help prevent surface flooding and reduce runoff.
Retention tanks are a great way to align your build with green building standards or environmental certifications. They also support climate resilience by making properties less dependent on external water sources during dry periods.
Our retention tank systems are designed for New Zealand conditions. Whether you need a standalone tank or a combined retention + detention system, we can help you size, design, and install a solution that works for your site.
APD’s retention tanks integrate seamlessly with our full range of underground systems — including StormLite®, StormSlim®, and StormSlab® — delivering a flexible, durable, and compliant solution for any project.
Detention tanks are an essential part of modern stormwater management systems, especially in urban and developed environments. Designed to temporarily store stormwater and release it slowly, detention tanks help reduce the pressure on public infrastructure, minimise flooding risks, and support environmentally responsible water management.
In cities and suburbs, impervious surfaces like roads, roofs, and driveways prevent water from soaking into the ground. This increases surface runoff, which can overwhelm stormwater networks. Detention tanks are used to slow the release of this runoff and manage peak flow rates effectively.
Local councils often require detention tanks for new residential or commercial buildings to meet consent and compliance standards. These tanks help prevent overloading the existing drainage systems, particularly in high-density areas.
Sites with poor drainage, steep slopes, or flood risk benefit from detention tanks. They control the flow of water and reduce the likelihood of erosion and property damage during heavy rainfall events.
When multiple properties share drainage infrastructure, detention tanks help regulate the collective outflow and maintain stormwater compliance at a catchment-wide level.
Slowing stormwater discharge protects pipes, culverts, and public waterways from sudden surges of water, which can cause damage and long-term wear to community infrastructure.
Detention tanks do not store water for reuse—that’s the role of a retention tank. Instead, they temporarily hold stormwater and discharge it at a controlled rate back into the stormwater system.
We offer engineered detention tank solutions that meet council regulations, are designed for New Zealand conditions, and are easy to install. Whether it’s a StormLite®, StormSlab®, or a custom build, our team can support your project from design to delivery.
Stormwater management of urban catchments rely on effectively controlling the volume and flow of runoff. Greenfield and brownfield sites in areas where planners and developers are providing intensification often create more impervious area, meaning more runoff at a faster flow rates compared to pre-development scenarios. Stream habitats and existing infrastructure are sensitive to changes in both flow rates and total volumes: so flood management and catchment often call for detention and retention.
Understanding the nuances between detention and retention are key to successful stormwater design and meeting consent requirements throughout New Zealand.
Detention seeks to reduce the peak discharge flow rate through the temporary storage and controlled release of stormwater. Most councils require post-development flows to not exceed pre-development flows, with some consents requiring a reduction in runoff. Mitigating frequent storm events helps manage limited pipe capacity in downstream networks and provides stream bank erosion protection, while detention of larger storm events is useful for flood mitigation.
Detention structures will typically have an inlet, outlet with flow control (often an orifice), and an overflow. During a rainfall event, water builds up in the tank while the flow control releases the water slowly, and the overflow prevents flooding during a large storm and regulates the total storage volume. Requirements for detention volumes can be found in local stormwater management guidelines, APD can provide assistance if you need help for your local project.
Retention of stormwater reduces the total volume of runoff from a site. This can be achieved by storage for reuse, soakage or evapotranspiration: unlike detention, water entering a retention device will not leave via an outflow pipe. Retention helps manage demand on town water resources, and reduces the total volume of water discharged to sensitive aquatic environments.
Retention tanks will typically either allow water to infiltrate into the ground, or contain a pump to allow for non-potable reuse like toilets, garden irrigation or fire suppression. Retention can also be achieved using green assets like permeable paving, living (green) roofs and rain gardens.
Some councils in New Zealand require a combination of retention and detention. Auckland’s Stormwater Management Area – Flow 1 and Flow 2 (SMAF) areas require a combination of retention and detention. For impervious areas where hydrological mitigation is required this typically this involves:
Stormwater storage tanks are a space and cost efficient way to meet detention and retention requirements on intensive urban developments. APD has a market-leading suite of stormwater management solutions to suit any site requirements.
APD’s in-house design tools and technical support allow us to provide detention and retention within the same tank. We give accurate tank dimensions and pipe level information to specifiers, contractors and councils, adjusted for each tank. Ask APD how we can help meet the detention and retention needs for your next project.
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