How do you figure out the weight of water in tank when full?

For a round tank you must find the volume of the tank - V (cubic ft) = pi x radius squared x the depth or height of the tank. The radius and the depth are in feet.

Next take the volume x 7.47 = Gallons of water in the tank

The weight of the tank is the weight of the water x 8.4

example: A water tank that is 2 ft. in diameter and has a height of 5 ft.

The radius is 1/2 of the diameter.

V = 3.1416 x 1 x 5 = 15.708

15.708 x 7.47 = 117.34

117.34 x 8.4 = 986# approx.