Built for Tight Spaces.
Ready for Council
Sign-Off.
Promax Slimline Tanks are engineered to meet New Zealand’s toughest urban building constraints. Low-profile, high-capacity, and delivered with free PS1-certified seismic restraints.
Our tank are made from a one-piece UV-stabilised polyethylene body with integrated seismic restraints arrives ready to bolt down, certified to AS/NZS 4020 (potable water) and comes with a PS1 for the seismic restraints.
Super Duty ENDURO
Underground Tanks
Choose this model when water must be potable or the site demands maximum structural strength.
- 60% heavier shell than the standard Enduro (10,000 L: 810 kg vs 500 kg) for deeper burial and heavy-vehicle loads
- Solid-filled ribs plus rectangular body cut excavation by up to 30 % while resisting extreme ground pressure
- Extra mass lowers uplift risk in high water tables, reducing restraint hardware
- Supplied with PS1 and optional cast-iron traffic lid for rapid council sign-off on critical infrastructure
- Certified for drinking water – first NZ underground tank approved to AS/NZS 4766:2020
ENDURO
Underground Tanks
Ideal for budget-conscious projects needing compliant stormwater or wastewater storage with traffic rating.
- Rectangular shell cuts excavation and back-fill by up to 30% compared with round tanks
- Roughly 40% lighter than Super Duty, so cranage and positioning cost less
- Solid-filled ribs and traffic-rated lids handle driveway and car-park loads
- Lower price point frees budget for other site works and fittings
- Capacities from 2,000 L to 10,000 L with garden lid standard and optional cast-iron upgrade
XPRESS
Underground Tanks
Best pick when you need big volumes, quick delivery and sharp pricing. (South Island Only)
- Cylindrical design delivers capacities from 1 000 L to 30 000 L for high-demand sites
- Lowest cost per litre in the Promax underground range, achieve big volumes while keeping capital budgets tight.
- Vehicle-traffic rated, engineered to support vehicles so tanks can sit beneath drives and car parks
- Twin inlet-outlet panels – simplify on-site plumbing now and futureproof system upgrades
- Rotationally moulded in NZ from UV-stabilised polyethylene and backed by a 5-year warranty
Accessories For
Underground Tanks
Add these when you want faster installs, firm ground-hold and smoother council sign-off.
- Engineered Uplift Restraints & Anchors – modular straps and concrete pads secure tanks in high water tables; PS1 drawings included
- Adjustable Trafficable Risers & Lids – poly or cast-iron (Class B/D) risers tune to finished ground level and bear vehicle loads
- Stormwater Fitting Kit – pipe seals, mesh screen and blank orifice plate cut plumbing time and speed council sign-off
- Complete Compatibility – purpose-designed for ENDURO, XPRESS and Super Duty tanks, giving a seamless fit and one warranty
TankGuard® Overflow Protection,
Keep Your Detention System Flowing
Promax TankGuard is the patented safeguard that stops leaves, silt and litter clogging your tank’s orifice, so every storm drains exactly as designed. Installed factory-plumbed and tested, it delivers controlled discharge without extra on-site work.
- Self-clearing mechanism positions the orifice in the overflow path; rising water flushes away any debris before it can choke the outlet
- GD01 compliant solution councils recognise for reliable, low-maintenance detention performance
- Proven engineering – performance verified through extensive testing for 1-in-6-month Auckland rain events
- Ready to drop in – shipped pre-assembled from our factory, saving time and ensuring correct installation first time
- Exclusive to Promax – TankGuard technology is available only with our underground ranges, giving you a single warranty and point of support
Installation and Council Compliance
- Full PS1 engineering pack supplied – includes traffic-load and uplift-restraint calculations for residential, commercial and industrial sites
- Shallow rectangular profile reduces dig depth and meets most council boundary-setback rules for detention and wastewater systems
- Free underground install guide covers bedding, back-fill, riser alignment and drainage connections from start to sign-off
- Pre-moulded 110 mm outlet and spare ports make council inspections easy and allow future plumbing upgrades without core drilling
Browse Slimline Tank Range
- Low height profile meets NZ height-to-boundary rules.
- Free seismic restraints supplied – no extra kit, installs 30 % faster.
- One-piece body – zero joins, welds or internal bolts that can leak.
- UV-stabilised food-grade material with a 5-year warranty.
- Integrated pump cover on 2000 L, 3000 L and 5000 L models.
- Super-narrow 1000 L (310 mm) ideal for gardens
Browse Tank & Pump Combos
- Factory-assembled packages that cut on-site labour
- 50 LPM jet pump, at mains pressure.
- Automatic mains change-over device included and pre-plumbed.
- Ready to bolt down and connect.
- Two-year pump warranty, AS/NZS 4020 approval.
- Ready for use as dual-purpose retention/detention tank
Watch Our Slimline Tank Overview
Dive into our blog
6 Reasons Why Builders, Drain Layers and Plumbers Choose Promax Slimline Tanks
New Zealand's urban development means plumbers, builders, and drainlayers face the challenge of adapting to shrinking residential spaces. Section sizes have decreased significantly over the past three decades, with new builds now occupying median sizes of less than 500 square meters. As these changes reshape the construction and plumbing industry, the need for innovative solutions becomes paramount.
Installation and Council Compliance
- Seismic restraint with PS1 included – suits residential, commercial and industrial builds.
- Height-to-boundary compliant for most councils – perfect for resource consent.
- Free installation guide covers stormwater detention and rainwater-reuse set-ups.
- Pre-moulded 25 mm outlet and extra boss positions simplify council inspection.
Need documents now?
Tick “Send Slimline Specifiers Pack” in the form and we’ll email CAD/PDF drawings, the PS1 certificate, plus install and maintenance guides.
For drawings, seismic information or expert advice, call 0800 77 66 29 or use the enquiry form below.