Preventing the Formation of Ice in Water Storage Tanks
One very simple method to prevent or minimize the formation of ice in water storage tanks is to allow the tank to drop the head as much as possible (to the lowest water level and/or pressure that the owner is comfortable with) before starting to pump again. The reasoning behind this method is that more warm water will be added to the tank during each pumping, as well as getting a much higher percentage of the water being agitated.
Conversely, if the water level is kept within a couple feet of the high water level (HWL), the pumps are running more, and the water that is added remains near the bottom of the tank, and is the first to be removed. This allows the water near the top to cool, and ice to form.
By allowing the head in the tank to drop lower, the average residence time of water in the tank is more uniform, the water is in motion for a greater amount of time, and the pumps are in use for a smaller percentage of time, with fewer starts.
In tanks where this is feasible, lowering the HWL in conjunction with the above method will result in a higher water turnover in the tank, more water movement, higher water temperatures, and a lower possibility of ice formation.
A second alternative is to use a water agitator, or “de-icer.” These basically consist of a motor/blade assembly which acts as a propeller to churn the water, the agitator should be located several feet below the water service level, such that it remains under water. The reasoning behind this method is that simply keeping the water in motion prevents ice from forming.
Preventing the formation of ice in tanks can be critical in the value of the tank. Ice formations can damage the tank, tank coating, and possibly piping. Damaged tank coatings can lead to corrosion of the tank, causing structural damage. By preventing ice from forming, the owner can reduce maintenance and reconditioning costs as well as extending the life of the tank.