A weekend in the desert ends with a rig carrying a meaningful quantity of Nevada home with it. Silt in every seam, brake dust turned to paste, a radiator packed solid. The cleanup is not optional and it is not gentle. It wants volume, it wants pressure, and it wants somewhere for a few hundred gallons of muddy runoff to go that is not the neighbour's driveway.
People building a home shop budget carefully for the parts they can see. Lifts, compressors, lighting, a floor that can take a jack stand. Water tends to get decided late and cheaply, usually a single hose bib on the outside wall left over from whoever owned the place before. That works until the first real post-race cleanup, and then it does not, because one undersized line feeding one spigot cannot keep up with a wand and a bucket at the same time.
The things worth settling early are unglamorous. Where the hose bibs go and how many. Whether the line feeding them is sized for two things running at once. Whether there is a utility sink inside the shop, because washing parts in the kitchen stops being funny quickly. Where the water leaves, and whether it leaves toward a drain or toward a fence line. Frost is a smaller worry here than most places, but a line run across an uninsulated wall still finds January.
That is a conversation to have with somebody who does this for a living, before the slab goes down rather than after. Kingdom Plumbing works in Las Vegas and is the kind of local outfit worth talking to while a shop is still lines on paper. We have no arrangement with them and are not speaking to anyone's pricing. We are saying that the plumbing decision arrives earlier in the build than most racers expect it to.
The retrofit is the expensive version of this. Cutting a trench through a finished slab to add a drain costs several times what the drain would have cost during construction, and the shop is unusable while it happens. Everyone who has done it once mentions it to everyone building their first.
Nobody starts a shop project thinking about where the mud goes. The people on their second shop start there.