The Mix

Every winter, water utilities across the United States and Canada deal with the challenges of cold weather, including main breaks and equipment outages. While these emergencies come without warning, they are obvious and visible when they do occur. But in other parts of the water distribution system, cold weather can create risk that is hidden from view: ice formation inside water storage tanks.

Often, the only time operators realize they have a problem with ice in their tanks is when it’s too late: after a tank’s interior is damaged or when the tank wall is punctured. Few operators climb and inspect their tanks in winter, so the extent of ice formation inside of water storage tanks is often unknown. Below we have compiled five factors that indicate your tank is at risk for ice formation.

Water is an unusual liquid. In warm temperatures, the warmer more buoyant water will rise to the top of a tank and the cooler more dense water will sink to the bottom. In the winter, when water cools to its freezing point, it becomes lighter and floats to the top. As you heat up water from its freezing point, it gets heavier for the first few degrees and is at its densest at 4°C above freezing. It can all seem very counterintuitive! If you decide to use a heater inside your storage tank to prevent ice formation, you will have to overheat the water to make it buoyant enough to float to the top. This will require a lot of extra energy. By combining heating with active mixing, you can actually keep the tank ice-free during the winter and use substantially less energy.