If you have a 1000 gallon container of water that has a half inch pipe coming out the bottom of the container what is the psi at that pipe and does the height and circumference of the container matter?

Answer 1

Shape matters First, the shape of the vessel matters. The outward pressure applied to the inside of the walls of the vessel is not unifom, regardless of its shape, but it will be more uniform for cylindrical vessels and more uniform, still, for spherical ones. Second, be advised that the contributions below apply more to water columns than to vessels. The pressure is all dependant on the height of the column of water. Calculate the weight of a 1 ft by 1 ft column of water to the height of the column. It doesn't really matter if the column is ACTUALLY 1 ft by 1 ft, the physics works out that way. Simply said, if the height of the container is 10 ft, that would give you a 10 cubic ft column of water. Ten cubic ft of water would be about 74.8 gallons. A gallon weighs about 8 pounds, giving you a column of water that weighs about 598 pounds. That would make the pressure at the bottom of the tank 598 pounds per square foot. To convert that to inches, divide by the number of square inches in a square foot, which is 144, leaving you about 4.1 PSI, if the water column is 10 ft high. Pressure at the bottom of a water tank Since for practical purposes, water weights approximately 8.34 lb. per gallon, 1000 gallons of water would weight 8340 lb. The bottom of the container does matter, as the 8,340 lb. would be distributed evenly over the entire surface area of the bottom. The wider the tank, the lower the psi. Conversely, the narrower the tank, the higher the psi. The water will exert exactly the same pressure per square inch on a 1/2 inch pipe as on a 1 inch pipe or a 6 inch pipe. To calculate the pressure at the bottom of the tank, calculate the bottom surface as Pi times radius squared. Example: with a 3-ft diameter tank: 3.14159 X 2.25 = 7.06858 sq. ft. (Pi times the radius squared.) Therefore 8,340 lb. per 7.06858 sq ft = 8,340 lbs per 1017.87 sq in = 8.194 psi. Calculate pressure for other diameter tanks by simply substituting the diameter in the above example.

The only factor that would effect the answer to your question would be the depth of the water. One foot of fresh water depth will exert .43 psi on a gauge. The size, shape and configuration of the container have no bearing on it. If you had a gauge at the bottom of a million gallon swimming pool that was 10 feet deep and you had a gauge at the bottom of a 4 inch pipe that was running vertical 10 feet deep (approximately 6.5 gallons) both gauges would read 4.3 psi.