Karen Mancl, Professor Food, Agricultural and Biological Engineering, The Ohio State University
Water towers are icons on the rural landscape and help people locate small communities from miles away. Elevated water tanks are the most visible portion of a water system. In addition to providing water pressure, these large tanks provide water storage. Water storage systems meet several needs.
The demand for water at one time of the day may exceed the yield in gallons per minute of the water source and the treatment plant. Water storage tanks accumulate water throughout the day so it is available to meet peak demand.
Storage tanks are made of concrete, painted bolted or welded steel, glass fused steel or factory coated epoxy steel. Concrete is the only material suitable for in-ground storage. Welded painted steel is the only material suited for elevated tanks. All types of tanks can be placed on top of the ground, but material selection means trade-offs. The most expensive materials need little maintenance, while lower cost materials require more maintenance.
Storing enough water to meet community needs for at least 24 hours allows for flexibility in the operation of the water system. Treatment units can be operated during a standard day shift to fill the tank, storing water for night-time use. Reserve capacity in storage helps a community deal with power outages and water system emergencies.
Reserve capacity is also important for stream water sources if a contaminant spill occurs. The water system can turn off the intake as the contaminants flow by, drawing instead from clean water in storage.
Water in storage is available to help fight fires. Remember, many small water systems cannot afford to store enough water to fight fires with potable water. In these cases, the drinking water system supplements the other water sources to fight fires.
Yes. Finished water is treated with chlorine to provide residual disinfection throughout the distribution system. If stored too long, the chlorine can dissipate, losing the residual protection. Also, water stored too long can taste stale and pick up metallic tastes from tanks and pumps.