15% off every standard 1.2m XPRESS. Until 31 October.

Every standard 1.2m XPRESS underground tank and the 900mm compact are priced 15% below retail on orders placed by 31 October 2026. The price on this page is the sale price, with the retail price shown alongside so you can see the saving.

Pick a size and your Promax rep confirms the tank at the sale price, plus delivery if you want it on site. The 1.9m XPRESS is priced on enquiry and is not part of the sale.

The 1.2m and the 900mm are built in the South Island and sold there. The 1.9m is built in the South Island and sold nationwide, with freight quoted with your order wherever the job is.

For a North Island site, ENDURO is the range to start with: it is built in the North Island and covers 1,000 to 10,000 litres. See the ENDURO range.

Every XPRESS underground tank travels free to your nearest Mainfreight depot, free to your site inside the Christchurch Metro area, and you can collect from Promax instead if that suits the job. If you want the tank delivered to site, your Promax rep arranges it and quotes it with your order, so the tank and the freight are priced together before you commit.

The volume is not ours to pick. It comes from your resource consent, or from the engineer who did the stormwater design, and it is usually written in litres or cubic metres.

If you have that number, go straight to the sale sizes and pick it. If you do not have it yet, send us what you do have and we will tell you what is needed to size it.

The 1.2m covers 2,000 to 10,000 litres and suits most jobs. Because one diameter runs across the range, the hole and the install detail stay the same and only the length changes: 2,000 litres is about 1.95 metres long, 10,000 litres about 8.75.

Choose the 1.9m when the volume is large and the trench cannot be: 10,000 litres sits in 4.25 metres on the 1.9m. Choose the 900mm when access is narrow or the volume is small.

Only with the right lid and riser. The standard polyethylene lid supplied with the tank is for garden areas. For a pedestrian or trafficable area the installation guide calls for a steel manhole lid and a Promax adjustable riser, which takes a concrete surround so vehicle loads are carried by the concrete and not the tank.

Tell us what goes over the top, whether that is foot traffic, cars or heavy vehicles, and we will confirm the right lid and riser to order with the tank.

An empty tank in saturated ground wants to lift. Uplift restraint kits and installation anchors hold it down, and they are sized to the tank: one kit per 1,000 litres on the 1.2 m tanks, and one per 2,500 litres on the 1.9 m.

Stated burial depths in the installation guide assume dry ground with no hydraulic loads, so if groundwater is a known issue on your site, say so when you enquire and it goes into the spec.

Potable water, stormwater retention and detention, and waste storage. A single tank can do two jobs on the same site, holding back stormwater during a rain event and storing water for reuse, as long as the design allows for it. Tell us the application when you enquire and it goes into the spec.

Pro-rata, from the date of purchase, per the Promax Warranty Terms and Conditions: 5 years on standard Promax underground tanks, which includes the XPRESS underground range.

The warranty covers the tank. Lids, fittings and inlet and outlet connections are excluded. The tank must be registered on promax.co.nz within 30 days of delivery.

A drainlayer, working to the Promax Underground Tank Installation Guide that comes with the tank. Excavation, bedding and backfill all matter on an underground tank, and connecting into the drainage is restricted work in New Zealand, so it has to be done by a registered drainlayer.

Your project location, the application, the required volume, site conditions, consent notes, and any plans or outlet specifications you have. Nothing needs to be finalised before you make contact.