I'm looking for a software which is able to simulate transient waterhammer effects in a pipe network. Ideally the software should handle both water, steam and air and have the possibility to include pumps, valves, vacuum breakers and so on. However, this kind of software seem to be pretty rare... Does anybody have a clue about a software which have at least some of these properties, or where to look for it?

Dear Sir, your inquire interests me. We have done some work about numerical schemes for wave problems in 1d system of water-gas-vacuum ( Journal of Computational Physics, v128, no. 2, 1996 ). Now we have included elastic-plastic solids into the system. Maybe our results can be applied to the water hammer phenomen you are working on. Also, we have a corresponding code, but not a commercel one.