Collecting rainwater to use for irrigation purposes can be an easy and cost-effective way to save water (and lower your water bills, of course), whether you're operating a large-scale commercial irrigation system or a simple set of lawn sprinklers. However, you have a number of decisions to make when choosing a rainwater collection tank, and choosing the material your tank is made from is one of the most important. Consider the individual pros and cons of the following tank materials before you hand over your hard-earned cash:
Concrete tanks
Used extensively on farms and other commercial properties that require high-capacity irrigation systems, concrete tanks are extremely tough and durable and can be expected to last at least as long as the rest of your irrigation system. Because they are generally manufactured to order (although repurposed concrete tanks can also be found for sale) they are available in an enormous variety of shapes and capacities, allowing you to craft a tank ideally suited to your needs. They do not suffer from problems with corrosion, and when fitted with a suitable lid they allow no sunlight to enter the tank, eliminate algae problems.
However, having a concrete tank made to your specifications can unsurprisingly be quite expensive, and even a low-capacity concrete tank will be considerably more expensive than equivalent fibreglass or polyethylene tanks. Transporting a concrete tank can also be difficult and expensive, especially when used in isolated rural areas, and larger tanks will require professional assistance to be installed safely.
Fibreglass tanks
An excellent choice for inexpensive, low-capacity irrigation systems, fibreglass tanks are cheap and very light, requiring no professional assistance to transport and install. You can also find small-scale fibreglass bladder tanks if you intend to install a pump-less pressurised system.
However, fibreglass tanks tend to be quite fragile, cracking rather than denting under strain and impact damage, and should not be expected to last forever. Fibreglass tanks also tend to have thin sides, which increases the amount of sunlight that penetrates the tank and potentially allows algal blooms to form in your water supply. Choosing a black or dark-coloured fibreglass tank, or painting your tank with UV-blocking paint, is a good way to get around this problem.
Polyethylene tanks
Polyethylene is one of the most popular materials used for making rainwater tanks, and its combination of strength, durability, lightness and flexibility makes it idea for a wide variety of tank applications. While generally more expensive than fibreglass tanks, they are much cheaper than heavy-duty concrete tanks. And because they are made from the same materials that tanks liners are made from, they require no separate liner of their own.
However, choosing a polyethylene tank that will be stored outdoors can cause problems, as prolonged exposure to intense sunlight can cause polyethylene to perish, making it brittle and fragile. This can be avoided using the same UV-blocking paints used to protect fibreglass tanks, or by placing your tank(s) in a sheltered area.
