I need to know how to figure how many gallons of water do I have to pour into a 10" diameter pipe to get 5 pounds of head pressure if a 1 foot raise equals .434 PSI of head pressure. Thanks, Tom

If 1 ft of head gives 0.434 psi of pressure, then the height of the column of water you need is 5/.434 = 11.52 ft. So now simply calculate the volume of water in a 10" diameter pipe that is 11.52 feet long. The volume of a cylinder is pi*r^2*L, where r = the radius = 5 inches . Make sure that your units are all in inches (not feet). This gives the answer in cubic inches. You then divide this by a conversion factor of 231 cubic inches/gallon to get the answer into gallons. Post back if you need more help on this.