Higher average temperatures mean more water is drying up faster than imagined, and a means to save as much water during the rainy season is seen as a need in dry and arid areas. Even urban and suburban populations have seen its necessity, not only as greywater (non-drinking water for everyday household needs) but also as drinking water (with the correct cleaning and filtrating equipment). Which is why underground rainwater tanks have seen a rise in popularity in the past decade.
For home and property owners, the best solution to having access to clean water anytime is by installing an underground storage tank, commonly constructed from concrete or plastic materials. Since these are different materials, they have their own advantages and (sometimes) disadvantages. Learn why and which type of tank in your property you should install here.
Why choose underground water tanks?
As is always the case, stationary water will eventually turn stagnant and undrinkable. When water is stored at an optimal temperature and stored below ground, the water remains drinkable for years to come. In the case of underground water tanks, you’re basically making your own spring water, which is considered the best possible drinkable water.
Also, all roof-harvested rainwater is naturally acidic, especially with higher carbon dioxide levels in the atmosphere and even in areas with lesser human pollution. The carbon dioxide will then be absorbed as water condenses from gas to liquid. However, the acidity contributes to the natural process where rainwater—with the help of natural microbes found in the soil that help break down its acidity—will then become neutral potable water.
Why or why not concrete?
The natural properties of water make it so the water balances out to a neutral pH. A concrete tank is the only man-made receptacle that helps in this process, as the water absorbs the minerals from the concrete and will settle into a significantly less acidic state. Additionally, underground water tanks will keep the rainwater at the temperature that it is collected, which means the stored cold rainwater remains cold during the entire year, even in the summer months.
However, concrete can be more expensive and difficult to set up and remove, especially for properties with limited spaces. Concrete is not entirely known as a flexible material, so it will be affected by the freezing and thawing of the stored water in cooler regions. Since concrete is made with calcium carbonate, this makes concrete somewhat porous. The acidity of the rainwater as well allows absorption of the calcium from the concrete into the water, resulting in hard water, which may incur additional equipment for turning hard water into soft water.
Why or why not plastic?
Underground water storage tanks from plastic materials is moulded from UV-stabilised and food-grade polyethylene materials. Despite the notorious fragility of plastic, underground plastic tanks are built to last. Modern designs include ribs on their walls that make them capable of storing thousands of litres of water and also resistant to pressure. The plastic material makes this type of tank lightweight, which means easier installation compared to concrete tanks.
Plastic is definitely weaker than concrete; therefore, leaking and leaching are high possibilities. This is also more prone to bacterial development inside the tank that could contaminate the stored water. Cleaning and maintenance is another issue you will have to face in cases of contaminants and to make sure the next batch of stored water remains clean.
The final say
Both concrete and plastic underground water tanks have their advantages and disadvantages. Nevertheless, if you’re going to use the stored water as drinking and/or greywater, the water is perfectly safe for everyday use—provided you also install the correct pumping and filtration systems to ensure bugs, dirt and dust cannot contaminate the stored water. But remember, if you choose a reputable rainwater tank supplier and service, and with the right care and maintenance, these well-made tanks will easily outlast its owners.