Water tower are used to hoist water tanks above the ground. This is done to increase water flow pressure. A water tower can be done as high as desired. However, for one that is done with wooden poles, the highest it can be hoisted is 20 ft above ground.
Water towers are often built and used by those who doing irrigation. Domestically, one can be built to increase water pressure into a building. Wooden water towers are as safe as those made of steel and are inexpensive.