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Slimline Water Tanks · NZ Made

The space-saving water tank for narrow sites, renovations and new builds

From 1,000L to 5,000L. Stormwater compliant. Built-in IL2 seismic bracing. Manufactured in New Zealand — with expert advice for your exact site, size and pump setup.

  • ✓ Help choosing the right size for your roof catchment and section
  • ✓ Help choosing the right size for your roof catchment and section
  • ✓ Quotes for single tanks, tank + pump combos, or multi-tank setups
  • ✓ Fast answers on stormwater compliance, PS1 and delivery to your region
Get Slimline Advice Browse the Range

Talk to a Slimline Tank specialist

Tell us about your site — we'll reply within one business day with sizing, pricing and availability.

Trusted by NZ homeowners, builders and specifiers since 1985.
5-Year Warranty
Made in New Zealand
7 Colours Available
Stormwater Compliant
Built-in IL2 Bracing
PS1 Available
Why a Slimline tank

Built for the spots a round tank can't reach.

Tight side yards. House-to-fence gaps. Townhouse and infill sections. Renovations where the section is already full. Council stormwater requirements that need a tank to disappear down the side of the house.

  • Narrow profile so it fits where round tanks won't.

  • Keeps yard space usable — no cylindrical footprint eating into lawn or driveway.

  • Stormwater compliant to meet council detention and retention requirements.

  • Engineered with IL2 seismic bracing built in as standard.

  • Seven colours to match cladding, fences or roofline.

Pick the right size

Which Slimline tank suits your project?

Use this as a starting guide — or let us size it for you based on roof catchment, household size and any stormwater requirements on your consent.

5,000L
Larger domestic demand

Best for bigger roof catchments or whole-home rainwater use, where you need serious capacity but still can't fit a round tank.

Tank only+ Pump combo
View Options
3,000L
Popular balance

Our most specified Slimline for family homes that still have narrow access. Great for toilet and laundry supply with a pump combo.

Tank only+ Pump combo
View Options
Most popular
2,000L
Compact all-rounder

A strong balance of capacity and footprint. Common choice for renovations and townhouses. Available as tank or tank + pump combo.

Tank only+ Pump combo
View Options
1,000L
Smallest footprint

For the tightest side yards and smallest catchments. Ideal top-up tank or garden supply where space is extremely restricted.

Tank onlyGarden use
View Options

Need more than 5,000L? Link multiple Slimlines with a Tank Balancing Kit for a bigger total capacity.

Help me size a multi-tank setup
Browse the range

Slimline tanks and tank + pump combos

Eight Slimline options, from compact 1,000L through to 5,000L. Not sure which one? Send your site details and we'll recommend the right match.

Trusted across NZ

Homeowners, builders and specifiers rely on Promax.

From one-tank renovation installs to commercial multi-tank setups, Promax has been New Zealand's rainwater and stormwater specialist for decades.

★★★★★

The Slimline fit perfectly down the side of our villa — total lifesaver on a narrow Auckland section. Advice on the pump combo was spot-on.

Rachel K. Homeowner, Auckland
★★★★★

We spec Promax Slimlines on townhouse builds because the stormwater compliance and PS1 are sorted. Delivery has always turned up when promised.

Daniel M. Registered Builder, Hamilton
★★★★★

Linked three 5,000L Slimlines with balancing kits for a build. Promax sized the whole thing and the install went in without drama.

Anna P. Specifier, Wellington
40+
Years NZ manufacturing
IL2
Seismic bracing standard
7
Colours to match your home
5yr
warranty
Delivery & project fit

Your region. Your site. Your project.

Slimline tanks go into some of the tightest spots in New Zealand — so site fit and delivery matter. Before you order, we'll make sure the size, access, colour and setup all line up with what's actually on your site.

  • Nationwide delivery

    We deliver Slimline tanks across the North and South Island. Freight is confirmed with your quote.

  • Access and unloading

    Narrow driveways, steep sites, rural access — tell us what you're working with and we'll plan for it.

  • Stormwater & compliance

    We can support stormwater retention/detention requirements and provide PS1 documentation on request.

  • Fits your exact site

    We confirm dimensions, bracing, pump options and fittings against your actual site before anything ships.

More complex project?

If you're running a multi-tank setup, a commercial project, a custom stormwater design, or a build with strict compliance requirements, talk to one of our specialists directly.

FAQ

Common Slimline tank questions

How narrow is a Slimline tank?

Slimline tanks are designed for tight side-yard situations — often as little as 600–800mm between house and fence. Exact dimensions vary by size. We'll confirm the exact width, height and depth against your site before you order.

Are Slimline tanks stormwater compliant?

Yes. Our Slimlines are used widely for stormwater retention and detention requirements on NZ consented builds. We can support the compliance side with PS1 documentation on request.

Do I need a pump combo?

Only if you want pressured rainwater supply into the house — for example toilets, laundry, or outdoor taps. Tank-only options are fine for garden and gravity-fed uses.

What seismic bracing do Promax Slimlines have?

Slimline tanks include IL2 seismic bracing as standard. For specific projects, PS1 documentation can be provided.

Can I link two or more Slimline tanks together?

Yes — multiple Slimlines can be connected with a Tank Balancing Kit to create a larger combined capacity.

Where do you deliver?

Nationwide across New Zealand. Freight is confirmed with your quote, including any site access considerations.

Ready to fit a water tank into that awkward space?

Send your site details and we'll get back within one business day with sizing, pricing and delivery for your region.

Phone
0800 PROMAX
Email
sales@promax.co.nz
Made in
New Zealand

Get Slimline advice

Quick enquiry — we'll reply within one business day.