TradesHow this works
Pressure loss down a pipe comes from three things: the friction of the water dragging along the walls, the fittings in the way, and any climb in elevation. This tool takes your flow, your pipe material and size, the length of the straight run, and the fittings on it, then works out the velocity, the friction loss, and the pressure left at the far end.
Fittings are handled with the standard equivalent-length method: an elbow or a valve behaves like a certain length of straight pipe, so the tool converts each one and adds it to your run before it computes the loss. Then it shows the size you entered alongside a size up and a size down, so you can see whether stepping up is worth it or whether you have room to go smaller and cheaper.
Common questions
What is friction loss in a pipe?
As water moves through a pipe it drags against the walls and loses pressure. The longer the run, the smaller the pipe, and the faster the flow, the more pressure you lose. Fittings like elbows and valves add loss too, which this tool includes.
How do fittings factor in?
Every elbow, tee, and valve acts like an extra length of straight pipe. This tool uses the standard Crane TP-410 equivalent-length method: each fitting is worth a set number of pipe diameters of straight run, which it adds to your measured length before working out the loss.
Why does velocity matter, not just pressure?
Water moving faster than about 8 feet per second is noisy and, over years, erodes copper. So even if a small pipe still delivers enough pressure, running it too fast is a reason to step up a size. The tool flags velocity as well as pressure.
Is this the same as sizing a new line?
It is the other side of the same coin. If you want the tool to pick a size from your fixtures and target pressure, use the Water Pipe Sizing engine. Use this one when you already have a pipe and layout and want the real pressure loss, fittings included.
Sources: Hazen-Williams friction method (US customary) · Crane Technical Paper 410 fitting equivalent length (L/D) · Copper Type L dimensions (ASTM B88), PEX (ASTM F877). Engine version 1.0.0. Risk tier 2.