I work for a plumbing company, and I'm trying to understand things like pressure loss etc. Right now I'm trying to figure out what's shown in the attachment. It is a pipe reduction with water flowing trough it. First, is it so that the flowrate at the left end must be equal to the flowrate at the right end? I believe it must be, otherwise water must be lost or gained as it moves through. If I'm right, does that mean that a house's need for water can be supplied through a whatever small pipe? If x liters per second go in on the left, won't that result in x liters per second on the right, only with much greater pressure? This is probably where pressure loss comes in. I just don't get how exactly... Last question; what equation links pressure and flowrate on the two sides? Bernoulli?