On a slightly related topic, does anyone know how water in a water tower is prevented from freezing during winter? I can’t believe the towers are heated. Is the water just recirculated constantly? Are the towers drained before cold weather sets in?
This is from howstuffworks-—
They do freeze. They just don’t normally freeze solid.
In the more extreme climates, like North Dakota, engineers incorporate heating systems into the tank design. Specifically, the central pipe that runs from ground level up into the bottom of the tank is called a riser. Water is pumped into the base of the riser and allowed to rise into the tank. Many tank risers are wrapped with heat tape, covered with insulation and capped by an aluminum jacket. In addition, a heating system may be installed in an adjacent building or into the valve pit underneath the riser. The heater introduces heated water or steam into the base of the riser. In either case, the heat rises into the tank to retard freezing.
Why don’t water towers freeze solid in the winter? | HowStuffWorks
https://science.howstuffworks.com/engineering/structural/water-tower-freeze.htm
Tough Winter Leaves Municipal Water Towers Frozen
https://minnesota.cbslocal.com/2014/04/14/tough-winter-leaves-municipal-water-towers-frozen/