I feel like this should be readily available, but I cannot find any information about it through google. I am trying to find a formula that will tell me the amount of energy necessary to inject water into a system at a given pressure. Put another way: I have a pipe of a known size and water (pipe a) is flowing through it at a know pressure (pressure x). I want to hook a pipe (pipe b) up to that original pipe a to inject additional water into it. I want to make sure that I am injecting the water into that system at a fixed flow (measured in GPM). I need to find out how much energy (say in horsepower or kPA) I would need to use to inject the water. or graphically what is the energy necessary to inject a constant stream of water at point O, given pressure x?: PIPE A (pressure x) -O--------->->->->----------------->->->->---------- | ^ |P |I |P |E ^ |B | I know that if pressure x is low, then I will not need very much energy to inject the water into that pipe, and if it is high, I will require quite a bit of energy. I however, do not know the specific formula that is used to calculate this energy requirement. Any links, or simply the formula, if known, would be greatly appreciated. Thanks very much.