Thank you all!
Ok. I understand that id depends on the aplication, and for example if we have the kind of situations exposed by "Scotsinst", we definatly must use 3-way valves.
But, still i have a question regarding this issue of the 2 or 3-way valves, also exposed im my other thread: when using a 2-way valve, there are changes in the flow rate, and consequently in the fricton losses. This induces some kind of dynamic behaviour in the system with implications on the pump.
My question is: how is the pump dimensioned in this case?
Thanks