Discover Promax Large Water Tanks

Household rain supply usually starts at 25,000L. Rural supply and fire reserve: 25,000L to 30,000L, often several tanks linked together. 10,000L and 15,000L suit stock water, irrigation top-up and smaller households. A useful rule of thumb for rain harvesting: every 1mm of rain on 1 square metre of roof collects 1 litre of water, so a 150 square metre roof in 1,000mm-a-year rainfall can harvest around 150,000 litres annually. Not sure? Send us your details below and we will recommend a size within one business day.

ENDURO is our strongest tank: corrugated walls, up to seven colours, and the only large tank that can be partially buried. XPRESS delivers the same Promax quality with smooth walls and the sharpest price per litre, in two colours. Both carry the same 20-year warranty. If you are unsure, the ENDURO is the safe pick for most homes and farms.

Yes. Promax tanks are made from premium UV-stabilised polyethylene that we blend in-house, compliant with AS/NZS 4766 and suitable for storing potable water. Poly will not rust, crack or leach like some older tank materials, and the sealed one-piece construction keeps light and contaminants out of your stored water.

Decades. Our UV-stabilised polyethylene is engineered for New Zealand's harsh sun, and the one-piece construction means there are no joins or seams to fail. Every tank on this page carries a 20-year warranty. For real-world proof, the 28 ENDURO tanks at Waiau went through the magnitude 7.8 earthquake without a single failure.

Only the ENDURO. Its corrugated sidewall is strong enough that large ENDURO tanks can be inset up to 1m and keep their full 20-year warranty - useful for downpipe fall, sloping sites, frost-protecting your pipework, or keeping the tank out of sight. XPRESS tanks are above-ground only.

Poly tanks need a flat, level, well-compacted base that fully supports the tank floor and is slightly larger than the tank's footprint - compacted basecourse topped with sand or crusher dust is the common approach. Keep the pad clear of roots, rocks and sharp objects. Full site preparation guidelines are on each product page, and our team can talk you through your specific site.

Tanks are made to order at our North Island and South Island factories and delivered nationwide. Lead times are shown on each product page and again at checkout, so you know the timing before you pay. Delivery is arranged after you order and depends on your location - the team confirms the details with you directly.

Sale pricing ends Friday 19 June - or earlier if the limited sale allocation sells out first. Each tank is made to order, so once the allocation is gone, the pricing goes with it. While the sale runs, the prices on this page are live - what you see is what you pay at checkout.

Selling direct through the website keeps the admin out and the price down. Anyone can order online and pay by card. Sale pricing cannot be applied to merchant accounts.