Water storage, both for potable and utility water purposes, can be more complex than simple containment issues. In areas with an abundance of clean, clear water either through public utility or from deep wells, long-term storage may just be to use run-off water for irrigation or for unexpected power-outs for toilet flushing, or boiling. Arid regions of the country may represent totally different needs, as each gallon of water must be conserved and used wisely. Safe storage becomes an essential in these cases.
Safe Water Storage
Whenever water will be consumed, safety becomes an issue because the growth of both algae and microbes must be inhibited. Many algae and bacteria are light sensitive. Exposure of the water to sunlight can raise the rate of growth many times over what inhibited exposure would allow. Therefore, blocking the sun from the water contained inside becomes a primary consideration in the selection of plastic tanks for major water containment. All other factors being equal, the black color will block out the most light from the interior of the tank.
In addition to just the direct effects of sunlight on the water inside the tank, the tank itself may be a major factor in the safety and quality of long-term water storage. Many plastics, even sunlight stabilized, may suffer long-term degradation and yellowing as a result of continual exposure to long-term sunlight intensity in tropical or subtropical regions.
There may be a plastic taste imparted to the water, or other long term off-gassing effects of plastic as it ages, especially with water that may contain trace amounts of minerals and other contaminants. Black tanks would clearly outperform white or clear ones here also.
Free Warm Water
In areas where the stored water will be used for bathing, showers or washing clothes, black tanks purposely exposed to sunlight can significantly reduce purchase energy consumption and costs. These specific warm-not-hot water needed applications can also be a continual reminder to conserve energy as a habitual practice.
Black coloration of plastic water storage tanks also can mask other additives that may be in the plastic to make it less porous, stronger, or otherwise beneficial. The relative neutrality of black and its better fitting in with a wider variety of décor colors may also be important in keeping the value of property optimal wherever water tanks are an absolute essential and not a convenience option.