Simple device to improve mixing in storage tanks

Document Type

Conference Proceeding

Publication Date



Department of Civil, Environmental, and Geospatial Engineering


Algae and bacteria can grow in water storage tanks when the water is stagnant. Although many variations of storage tank exist, many have the inlet and outlet pipes at the tank bottom. Stagnation occurs in the top portion of the tank from which water is not used since it is kept for emergencies only. A simple and passive method was developed in this study that mixes water in the entire tank without using electricity like mechanical mixing devices. The new device consists of a riser pipe in the tank center that leads to eight-arm sprinkler-type piping that extends above the entire tank surface. Diffuser holes are located along the bottom of all the sprinkler arm pipes from which water falls even along the entire tank surface. To ensure that all water particles fall directly down and thereby mix all the tank’s water a corresponding “inverse sprinkler” is used for drainage out of the tank. This drainage sprinkler has eight arms with the same location of holes as the top sprinkler, this time on the top of the piping for the eight arms. The device requires only some additional piping be put into an existing or new tank. The new piping is low cost, since it could be from commercially-available seizes and material such as PVC. Laboratory experiments were conducted both with and without the new mixing device. Dye testing and detailed three-dimensional acoustic Doppler velocimeter measurements show a significant increase in mixing throughout the tank with no stagnation zones to allow the growth of algae or bacteria, thereby improving public health. The new device, therefore, is concluded to be an effective and passive and sustainable way to eliminate stagnation in water storage tanks and thereby improve public health.

Publisher's Statement

© ASCE 2019. Publisher’s version of record:

Publication Title

World Environmental and Water Resources Congress 2019