A city in Southern California owns and operates several storage tanks. Two of these reservoirs are oversized for emergency situations, and City staff constantly struggled to maintain water quality due to low demand and high water age. In an effort to improve the quality and reliability of its drinking water, the City researched various active mixing technologies. Two candidates were selected for a side-by-side trial to test their mixing performance in one of the City’s most problematic tanks: the PAX Water PWM 400 Mixer and a competitor’s lower-priced mixer.

Both manufacturers claimed that their products would be able to fully mix the tank, but the City required a performance test to evaluate these claims. Water department staff understood there was a significant price difference between the two units, but they wondered if mixing performance would be equal.