Kitchen Plumbing Calculator

Main Run Length dominates total pipe footage — it's the distance from your main supply/stack to the kitchen, and it feeds directly and repeatedly into the cold supply main, hot supply run, and drain run calculations. Its declared range (5-100 ft) produces a far larger swing in Total Pipe Needed than toggling any single appliance, which only adds a fixed handful of feet of branch piping.

No — Supply Pipe Material (PEX, CPVC, or Copper) only changes the cost per foot in the Estimated Material Cost figure, not the physical pipe footage in Total Pipe Needed, Cold Supply Pipe, or Hot Supply Pipe. Copper costs roughly three times as much per foot as PEX for the same layout, which is why material choice can swing your budget significantly without changing any of the length figures.

Toggling Dishwasher to 1 adds 2 fixture units (raising Total Fixture Units and potentially the required Drain Pipe Size), adds a hot water connection (since dishwashers need hot water, unlike an ice maker), and adds a few feet of branch and drain-tail pipe for its dedicated connection — it touches fixture units, hot supply length, and drain length simultaneously, not just one output.

Drain pipe size only changes when Total Fixture Units crosses one of two thresholds (3 FU or 6 FU). For example, a double-bowl sink alone totals 4 FU, comfortably within the 2" drain tier that covers everything up to 6 FU; adding a pot filler's 1 fixture unit brings the total to 5 FU, still under that 6 FU threshold, so the recommended drain size stays at 2" even though total fixture units did increase. It only takes a change that actually crosses 3 FU or 6 FU — for instance, a double-bowl sink plus dishwasher already sits right at 6 FU (still the 2" tier), and adding an ice maker's 0.5 FU on top pushes the total to 6.5 FU, crossing into the 3" tier — to move the recommendation to the next size.