Water layering and full-depth mixing: How water layering affects tank water quality, and why full-depth mixing is one solution

Potable water storage tanks, an integral part of a municipality’s water distribution system, provide pressure and enough supply for daily and emergency use. Yet the AWWA estimates that 65 percent of them have water quality problems. These problems—common in both chlorine and chloramine systems, warm or cold climates—can range from temperature stratification, stagnation, dead zones and short- circuiting to biofilm build-up, loss of residual, nitrification events and, in northern climates, ice damage. These problems occur because water in tanks forms thin horizontal layers due to differences in temperature and pressure. One solution with proven results is to mix the tank thoroughly, from tank floor to water surface. Understanding why water layering occurs in storage tanks will help utility managers determine how best to ensure the water their customers receive is of the highest quality. Learn more; download our white paper.