Regular clean outs and corrosion resistant coatings can be dangerous and expensive at over 100 feet off the ground. Probes, air vents, overflow devices, and sight gauges are a few of the necessary components that cause problems and add expense. Stale or warm water is possible in low flow conditions as the same water could remain in the tank for a long period of time. Pump cycling is not as much of a problem with elevated tanks as with pressure tanks but pumps will still cycle. Cost of at least six figures is a huge drawback of elevated tanks.
Fire protection is very limited.
In most applications, the main objective of elevated tanks is fire protection during power off conditions. If the water tower happened to be near full when the power went off, water pressure will be gone in a matter of hours. If you had to fight a fire during the power outage, water pressure could be gone in a matter of minutes. All these problems can be avoided if water can be supplied at the correct pressure and flow without storing water under pressure. Cycle Stop Valves do just that.