The Benefits of Mixers In Water Storage Tanks
Note: The following is an excerpt from the article of the same name written by Mike Moeller and published in ServiceLine (February 2019 Edition), the official publication of the South Dakota Association of Rural Water Systems (SDARWS).
Why use a mixer? The main benefit of using a mixer is that it keeps your water in the tank fresh.
If you don’t have mixer when the tank fills the warm water that was in the tank rises to the top and the new fresh water that is cooler in temperature stays at the bottom causing stratification. When stratification occurs, and the warm water stays at the top it never really gets used, and the disinfectants in the warmer water tend to dissipate thus raising the chance for bacteria to form in the warmer water.
When you use a mixer, the water is kept at a uniform temperature throughout the tank, and the disinfectants will remain in the water and prevent bacteria from forming. Another reason to have a mixer, especially in our winter climate, is to prevent ice from forming on the sides and top of the tank.
When ice forms on the side of the tank it reduces the capacity of the tank and can create problems with the coating on the tank. When the coating is compromised in the tank water can get to the steel under it and causes corrosion problems. If the tank has an ice shelf on the top, it can potentially slide down when the water level drops and shear off the bolts in a bolted tank design. If the water level drops a few feet before the ice shelf slides it could potentially create a vacuum inside the tank and cause the tank side walls to collapse inward in a worst-case scenario.
Lastly, if you are on a water system that uses chloramines as a disinfectant when the water in your tank becomes old from stratification the water on the top that is warmer will go through a microbial process that converts the ammonia into nitrates and nitrites. When this occurs, disinfection by-products will become present and can be potentially hazardous to your water system.
Written by Mike Moeller, SDARWS Technical Assistance/Training Specialist
You can find the full article at: www.sdarws.com/assets/february-2019-slweb.pdf