If you ask the right questions, you will buy the right tank. It sounds obvious, but a water tank is infrastructure you will live with for decades, and most of the regret we hear about traces back to a question nobody thought to ask before the order went in. The ten below are the ones that matter. Each one links to the full answer.
What size tank do I need?
Capacity is the decision everything else hangs off, and it is the one most often guessed. The honest answer depends on your roof area, your local rainfall, how many people are drawing off the tank, and how long a dry spell you need to ride out. Guessing low is the expensive mistake, because the fix is a second tank rather than a bigger one.
Work it out properly with the rainwater tank size calculator, or read what size water tank do I need for how the numbers fit together.
Is it OK to buy a cheap tank?
A cheap tank is only cheap once. The price gap between a budget tank and a properly engineered one usually shows up somewhere: thinner walls, less UV stabiliser, a shorter warranty, or fittings you end up replacing. None of that is visible on delivery day, which is exactly the problem.
We set out what actually differs in 7 risks with buying a cheap rainwater tank.
Are all poly tanks the same?
No, and this is the assumption that costs people the most. Two tanks can hold the same litres, sit on the same base and look broadly alike, while differing in wall design, raw material grade, and how tightly the manufacturing process is controlled. Those differences decide whether the tank is still sound in twenty years.
Not all poly tanks are made equal goes through what separates them.
Is a poly tank better than a concrete tank?
Both have their place, and the right answer depends on your site rather than on the material in the abstract. Polyethylene does not corrode, arrives in one piece so there are no joins to seal, and is light enough to install without heavy gear. Concrete brings mass, which matters in some situations and is a liability in others.
We compare them directly in concrete or plastic: which water storage tank is best.
How much will it cost to deliver my tank?
Freight is the line people forget, and on a large tank it is not trivial. Cost tracks size, weight and distance, and it can move the total meaningfully depending on where you are. South Island deliveries carry additional freight charges.
Ask for the delivered price rather than the tank price. It is the only number that lets you compare two quotes fairly.
How long will it take to deliver my tank?
Lead times stretch when demand spikes, and a tank that arrives after the concrete pour is a scheduling problem, not just an inconvenience. Ask whether a delivery date can be committed to rather than estimated, particularly if a build programme depends on it.
Current lead times are published here.
Is installation going to be expensive and complicated?
It depends almost entirely on what you are installing. A poly tank is light enough to place without a crane, which keeps installation simple and cheap. What matters more is the base: get that wrong and you have built a fault into the system on day one.
Start with selecting the best base for your water tank and how to install your water tank. For the work itself, we keep a list of recommended installers.
Are poly tanks safe for drinking water?
This is a fair question and it has a specific answer rather than a reassuring one. The standard to look for is AS/NZS 4020, which covers products in contact with drinking water. Ask whether the tank complies, and do not accept a general assurance in place of the standard.
More detail in are poly water tanks safe.
How long is the warranty?
Warranty length is the closest thing to a manufacturer stating out loud what they expect the tank to survive. Read what it actually covers and whether it is pro-rata, because a long headline number on a pro-rata basis is worth less than it first appears.
Our warranty terms are set out here.
What accessories and fittings are included?
Two quotes are rarely comparing the same thing. Leaf diverters, screens, outlets, and fire service fittings may be in one price and absent from the other. Get the inclusions listed before you compare, not after.
The full range of rainwater harvesting accessories shows what a complete system usually involves.
Now go and ask them
A manufacturer worth buying from will answer all ten of these without hedging, and will tell you when the honest answer is that it depends on your site. If a question gets a vague response, that is information too.
If you would rather talk it through than read ten articles, get in touch with our team. Tell us the roof, the site and what the water is for, and we will come back with a straight recommendation.