What pressure in pounds on a hot water boiler can push water up a pipe 28 feet high?

To determine the pressure required to push water up a pipe to a certain height, you can use the hydrostatic pressure principle, which states that the pressure needed to lift water is directly related to the height of the column of water and the density of the water.

Specifically, a rule of thumb is that it takes about 0.43 pounds per square inch (psi) of pressure to lift water one foot. Therefore, to calculate the pressure needed to lift water 28 feet, you multiply the height (28 feet) by the pressure required per foot (0.43 psi):

28 feet x 0.43 psi/foot = 12.04 psi.

This calculation indicates that approximately 12 psi of pressure is needed to lift water 28 feet. Given this consideration, the choice of 12 pounds correlates correctly with the required pressure to lift the column of water the specified height. This makes it the correct answer for the question posed.