This Solar-Heated Watering Tank (called the BT Sun Tank) is designed to keep water thawed for livestock even when the temperature drops down to -50 degrees Fahrenheit. It has a 2-inch-thick float valve on top, which the animals learn to push down to get the water, and a shatterproof solar panel attached to the front, which generates enough heat to prevent freezing, even if cloudy for a few days. In summer, the system can be de-activated by simply covering the solar panel. An additional year-round advantage of this product is that, because the float is on top, the water is protected from algae growth and disease-transmitting foreign matter (e.g., mosquito larvae, parasites, bird droppings). Insulated to an R-50 rating, the BT Sun Tank is available in 25- and 42-gallon sizes with manual- and auto-fill options.