In potable water, the biggest threat to water safety is unmixed tank contents. Inadequate mixing in potable water storage is a persistent problem for many municipal water systems that can lead to sampling inconsistencies, thermal stratification, old water age, low disinfectant levels, and other problems. Mixing tank contents consistently and continuously is key to maintaining water quality.
The American Water Works Association (AWWA) has noted that nearly two-thirds or more of tanks experience a loss of residual disinfectant when water temperatures rise during warm weather. This thermal stratification leads to a deterioration of water quality, especially in the upper part of the tank. When water stratifies, recently disinfectant-treated cold water is prevented from mixing well with the existing water. So the new water tends to stay near the bottom. Because that cold water near the bottom will be first drawn, water temperatures tend to separate more rapidly.
Thermal stratification occurs with even minor temperature gradients. Bacteria can grow rapidly in this kind of environment and ongoing stratification can lead to the breakdown of disinfectant additives. Stratification also introduces sampling inconsistencies that can lead incorrect application of chemical disinfectants. Since water quality testing is based on a variety of samples, the importance of accurate water readings can’t be overstated. Ensuring a complete mix of contents can be one of the most important factors in water tank maintenance.
Use of an internal water circulator like Kasco’s certified NSF/ANSI 61 & 372 CertiSafe Circulator water mixer will prevent thermal stratification and other issues. The submersible design allows for active tank mixing to completely aerate water, and utilizes human grade mineral oil and is free of zinc anodes to ensure the safety of your tank contents. Active tank mixing can provide consistent disinfectant mixing, eliminate thermal stratification and ensure that all of the water in the tank is of a uniform age. Water quality still has to be monitored on a regular basis to ensure that it meets requirements.