Concrete has a long reputation in New Zealand water storage, and that reputation does a lot of the selling. It is time to reveal some cold, hard facts. Before you buy a concrete tank on the strength of what everyone knows about it, it is worth testing the four claims underneath: that concrete is cheap, that it is strong, that it keeps water clean and untainted, and that it is easy to look after.
Where the concrete reputation comes from
A concrete tank looks like permanence. It is heavy, it is solid, and it has been used for household water for generations, so durability gets assumed rather than argued. That assumption is worth examining instead of inheriting. The four misconceptions below are the ones that come up most often when people are choosing a material, and each behaves differently once the tank is on a real site, full of water and expected to last. Take them one at a time and the picture changes. If you want the wider material comparison first, we have set it out in our concrete versus plastic comparison.
Misconception one: concrete water tanks are cheap
The price tag might look cheap, but you will pay so much more for your concrete tank in the long run. Because of its weight, transport to the site will cost a lot of money, especially if you live in a rural region. Heavy equipment, like an excavator or Hiab, must be hired, with industry experts suggesting installation costs could range between $1,000 and $3,000, depending on location. Burying a concrete tank is costly, while a botched installation could cost you hundreds more in additional materials and labour. The purchase price is only the part of the cost that is visible at the point of sale.
The warranty conditions attached to that price
Unless you follow the installation guidelines to the letter, the warranty becomes void. In most cases, a warranty does not cover damage caused after delivery resulting from inadequate site preparation, or tanks that are not placed directly onto a prepared tank site at the time of delivery, or damage caused during transportation or installation. Those are just a few of the warranty conditions. The practical effect is that the risk of a difficult delivery or an imperfect pad tends to sit with you rather than with the supplier, which is worth reading closely before you commit to a material on price alone.
Misconception two: concrete water tanks are strong
It is widely believed that concrete tanks are strong and durable. Try telling this to the couple who had their concrete tank filled with water only to lose all 22,000 litres through an unseen crack in just two days. What happened to them is not unusual. Cracking in concrete tanks is common because they are very rigid structures with no flexibility. Cracks can occur during the loading or unloading of the tank, if the ground moves when the tank is empty or, as was the case with our unfortunate couple, under the weight of a sudden dump of water from a water delivery transporter in dry weather. We compare materials on strength in which is the strongest water tank.
Misconception three: concrete water tanks keep water pure
Concrete is full of lime. If you install a concrete water tank, you can also expect a tank full of lime. When lime leaches into the water, it enters your home's plumbing system and damages tapware and other hardware. The expense of replacing these things, as well as filters, adds another cost you might not have thought of when you first saw that misleading price tag. Lime in the water is just one of your concerns regarding water quality. E. coli and other bacteria are also something to worry about, and that is linked directly to the next fallacy.
Misconception four: concrete water tanks are easy to clean
Anyone who tells you that concrete tanks are easy to clean is telling you a dirty lie. Concrete is a porous material, and because of this, it is a difficult surface to maintain and keep clean. This type of surface gives algae, E. coli and other microscopic bacteria plenty of cavernous spaces to hide away. They will eventually build up and contaminate the water in the tank. Porosity is not a cosmetic issue. It changes how much work keeping the water clean takes, and it keeps changing it for the whole life of the tank, as our guide on getting the cleanest water from your rainwater tank explains.
Our bias, stated plainly
These are just a few of the misconceptions about concrete water tanks. As polyethylene tank manufacturers, you might accuse us of giving you a highly biased view. That is a fair thing to hold against us, so we would rather say it outright than let you work it out on your own: we make poly tanks, and we think they are the better answer. We believe poly water tanks offer so many more advantages than concrete tanks that comparing them is a one-sided argument. Read what follows knowing exactly where it comes from, and test it against the other materials on your shortlist.
What a poly tank does differently
Let us start with the cost. The supply and installation costs for poly tanks can be less than half of those for concrete tanks. The lighter weight of a poly tank makes it far easier and cheaper to transport and install, because it can be lifted, rolled and handled by lighter equipment than you will need for a concrete tank. Poly tanks are stronger and more flexible than concrete tanks and better able to handle loading, installation, ground movement, and filling without cracking. They are non-porous too, so unlike concrete, they are easier to clean and maintain, and water quality and safety are enhanced. Algae, E. coli and other bacteria are much less of a threat in a poly tank than in a concrete one. We answer the safety question directly in are poly water tanks safe.
Making the comparison on your own site
Understandably, you will want to consider all materials when you are in the market for a tank. The point of the four misconceptions above is not that concrete never works anywhere. It is that each claim deserves testing against your own situation: how far the delivery has to travel, what equipment can reach the pad, whether the ground moves, and what you are prepared to do to keep the water clean. The same argument plays out below ground, which we cover in underground stormwater tanks, concrete or plastic. With a few cold, hard facts to guide you, you might see that some materials are better than others at providing reliable and safe household water storage.
Call Promax on 0800 77 66 29.