ditttohead
Water systems designer, R&D
We see this problem all the time, anything you add to the plumbing causes some pressure drop. A 90, extra length of pipe etc are all calculable. Even though these might be extremely small losses, cumulatively they can add up quickly. We see problems in the farthest runs with pex since all too often the plumber will use the smallest possible pex that works on paper, but with even the slightest variable, pressure drops at the end of these runs becomes very noticeable. If you ever have an old garden hose you are going to replace, try this experiment. Turn the water on full blast and see what comes out at the end of a 50' hose. It may seem like a lott but then cut the hose to 5' and see the massive difference. Frictional loss calculations are often ignored. Extremely long pipe runs act similar to capillary flow restrictors. These are tiny tube that we use a flow regulators. We simply make them longer to decrease flow. This works the same if the pipe is 1/32" or 2". The physics are basically the same.
