When discussing the respective merits of plastic water storage tanks and their concrete counterparts, there are no prizes for guessing where our loyalties lie. Promax is New Zealand's premier manufacturer of superior polyethylene water storage and transport products, and our plastic water tanks combine several significant advantages that make them the smartest choice for residential or rural settings. But this article is not entirely dismissive of concrete tanks. We are happy to list their major advantages alongside their disadvantages, and to be clear about the one thing concrete does that plastic cannot.
Where Concrete Tanks Have the Edge
Concrete earns its place on two counts:
- Concrete tanks can be buried underground. This is a good thing to do for aesthetic reasons, as burying them removes what can be a blot on the landscape.
- They keep water cooler, due to the insulation value of concrete.
Both of those are real advantages rather than marketing lines. If your priority is a tank you cannot see, concrete has an answer to that question. The rest of this article is about what you give up to get it.
Where Concrete Tanks Fall Down
- If your site is not accessible for a hiab or similar, the tank will have to be built on site.
- It is not easy to retrofit new outlets to a concrete tank.
- The tank may be damaged by earthquakes.
- They are more expensive to buy and install than plastic tanks.
Read that list again and notice how much of it is about the future rather than the day of delivery. A tank built on site is a tank you cannot easily move or replace. An outlet that is hard to retrofit is a plumbing decision you are locked into for the life of the tank. Those constraints do not appear in the purchase price, but they arrive eventually. We go further into this in the truth about concrete tanks.
The Case for Plastic Tanks
- Plastic tanks are lighter and easier to manoeuvre into position. Yet they are not lacking in strength: you can bury a Promax corrugated tank up to a depth of one metre.
- It is relatively straightforward to retrofit outlets.
- Because they can flex a little, plastic tanks can withstand earthquakes.
- They are a lot more cost effective than concrete tanks to buy and install.
- Promax ENDURO Aboveground tanks can be buried up to one third of their height in the ground.
The flex point is worth dwelling on, because it inverts the usual instinct. Concrete feels stronger, and held still it is. But a tank in an earthquake is not a static problem, and a material that can move a little without cracking has the advantage. If strength is your deciding factor, see which is the strongest water tank.
The One Real Limitation of Plastic
We will be straight about the trade-off. Most standard plastic storage tanks cannot be fully buried. If the tank being invisible is your single highest priority, that is a genuine point in concrete's favour and we are not going to pretend otherwise. In practice, you can help to hide a plastic tank with planting, and Promax ENDURO Aboveground tanks can be buried up to one third of their height in the ground, which takes a useful bite out of the visible portion. If full burial is what the site actually needs, that is a different product question, and one we cover in underground tanks: which is best, concrete or plastic.
The Standards Behind a Rotomoulded Tank
By choosing a Promax plastic tank, you are in good company. The rotationally moulded plastic water tank is New Zealand's most popular tank. One of the main reasons for this is that the rotational moulding industry has a comprehensive standard covering both the raw materials and the manufacturing of the completed water tanks. We construct these tanks from food-grade standard materials, compliant with AS/NZS 2070: Part 1 and Part 8 Australian Standards for Food Contact. In addition, if the water in the tank is intended for human consumption, the plastic material must comply with the potable-water standard AS/NZS4020: 2002 Potable (Drinking) Water Standard. If that side of things is your concern, we address it directly in are poly water tanks safe.
Inert Plastic vs Alkaline Concrete
By its very nature, concrete is highly alkaline. Plastic, on the other hand, is inert. That has a practical consequence on day one: you can start using the tank straight away, without having to fill it up and then flush it out. It also has a consequence over the following decades. Polyethylene will not rust or suffer from corrosion in the same way metal and concrete do, which contributes to our tanks' long life. An inert material is not doing anything to the water it holds, and the water is not slowly doing anything to it either. Both of those matter when a tank is expected to last.
One Piece, No Joints, No Sealants
Poly tanks are typically made in one piece. There are no joints or seams where parts of the tank have been welded together, and no sealants are used to join pieces of the tank together. This is a quiet advantage that only becomes obvious with time. Every joint in any vessel is a place where two things have been made to meet, and it is the first place anyone looks when something eventually leaks. A tank moulded as a single piece does not have that category of weak point at all.
Algae, Sunlight and Material Choice
Algae needs light to grow, which makes the tank wall part of the water quality question rather than just a container around it. Promax only uses materials that comply with AS/NZS4766: 2002 Polyethylene Storage Tanks for Water and Chemicals that inhibit algae growth. Meanwhile, light transmission is a potential problem that fibreglass tanks need to manage. This is not an issue for our plastic storage tanks. It is one of those specification details that never comes up in a showroom conversation and matters every day once the tank is in the ground or on its stand.
Recycling at the End of Service Life
Polyethylene tanks can be recycled at the end of their service life, but they will not become water tanks again. This is because potable water regulations state that we must use only virgin plastics in new tanks. However, there are many other product applications for recycled plastic, and with the addition of sun and heat protection it can serve another vital purpose for many years. As a company that wants to do our bit to look after the environment, this sustainability is something we embrace.
We're loyal to plastic water tanks, and for many good reasons. Should you reach the same conclusion and want to know which Promax product will best suit your requirements, we're right here. Browse the water tank range, or contact us for further information and advice to help you make the right decision.
Call Promax on 0800 77 66 29.