Plumbing & sanitary: DN20 is a diameter, PN16 a pressure
A plumber writes “15x21 fitting”. A general-purpose engine sees a multiplication — and right next to it, “DN20” and “PN16” have exactly the same shape for two entirely unrelated quantities.
Two sizing systems, in the same catalog
This is the trade's particular inheritance. Nominal diameters are counted in millimetres — DN20, DN32 — and threads in inches, but written the French way: 15x21 for a half inch, 20x27 for three quarters. Both live on the same invoice, and a fitting is ordered in one system while the pipe it screws into is ordered in the other.
On top of that sits a pair nothing tells apart visually: DN20 is a diameter, PN16 a pressure. Two letters, a number, two unrelated quantities. The plomberie rule pack separates them, and with them the material and the gender of a fitting (the detail of each attribute).
Diameter, pressure and thread kept apart
The plomberie rule pack activates when you pick your industry, at indexing time. It produces these annotations, each of which becomes a usable filter:
| Annotation | What it isolates |
|---|---|
FILET_15x21 | the thread size in French inch notation |
DN_20 | the nominal diameter |
PN_16 · BAR_6 | the nominal pressure, however it is written |
TUBE_14X16 | a copper pipe's dimension |
POUCE_1/2 | the thread size in imperial notation |
GENRE_MALE · GENRE_FEMELLE | the fitting's gender, including the MM and FF abbreviations |
MAT_CUIVRE · MAT_PER · MAT_LAITON | the material, highly discriminating here |
PUISS_24KW | a boiler's output |
To these are added the six aisle families — fitting, pipe, valve, heating, sanitary, drainage — and the gender, which counts here as much as a dimension: a male fitting and its female counterpart carry the same thread and do not screw together. Three couplings follow from that, each repairing an ambiguity of the trade: RACC_20x27 attaches the thread to the part carrying it, TUBE_MAT_CUIVRE tells a copper pipe from a copper fitting — two aisles, two buying gestures — and VANNE_DN_25 keeps the diameter rather than the pressure, when “DN25” and “PN16” look stroke for stroke alike.
Five references, exactly as a supplier writes them
| Indexed reference | What the engine extracts |
|---|---|
| Raccord union laiton male 15x21 | FAM_RACCORD · FILET_15x21 · GENRE_MALE · MAT_LAITON · RACC_15x21brass male fitting, 15x21 thread |
| Vanne a bille DN20 PN16 laiton femelle | FAM_VANNE · DN_20 · PN_16 · GENRE_FEMELLE · VANNE_DN_20DN20 ball valve, 16 bar, female |
| Tube cuivre 14x16 barre 4m | FAM_TUBE · MAT_CUIVRE · TUBE_14X16 · TUBE_MAT_CUIVREcopper pipe 14×16 |
| Manchon 1/2 pouce laiton | FAM_RACCORD · POUCE_1/2 · MAT_LAITONbrass coupling, half inch |
| Chaudiere gaz condensation 24 kW | FAM_CHAUFFAGE · PUISS_24KW24 kW boiler |
“mm” does not mean male when it follows a number
The abbreviation for a male-male fitting is MM. So is the millimetre — and plumbing measures everything in millimetres. An engine that takes one for the other files half the catalog under the “male” facet, and that facet becomes useless without any search visibly failing.
The pack decides on what precedes: an mm following a number is a unit, anywhere else it is a gender. Measured on a catalog of three thousand references, the “millimetre” sense was three times more frequent than the “male” sense — meaning the confusion cost three false annotations for every true one.
What the pack does not recognize
Three points deserve to be stated before indexing.
Inches written with a double quote. 1/2" loses its unit as it is read: normalization only accepts the period, comma, slash and hyphen as internal separators, and the double quote disappears before the rule runs. Write 1/2 pouce or 1/2 inch and the annotation comes back — or use the French thread notation, which is the ordering spelling in France anyway.
Multilayer and PEX pipe dimensions. These pipes are written “outer diameter × wall thickness” — 16x2, 20x2 — with a single digit on the right, where the pack expects two. The pipe stays findable by its material and brand; its dimension does not become a filter. Copper pipes, written 14x16, do.
A thread is also annotated as a pipe. 15x21 and 14x16 share the same shape, and the pack does not tell them apart: a 15x21 fitting therefore receives a pipe-dimension annotation on top of its thread. No consequence for search — the fitting comes back fine — but a “pipe dimensions” facet built from these annotations would contain fittings. It is fixable, and what is missing is the standardized list of pipe dimensions, not a rule.
The taxonomy already built for you
The plumbing pack isolates the diameter, the pressure and the material as filterable attributes, not as text. You can then offer a “20x27 brass fittings” or “DN25 PN16 valves” page without building the taxonomy yourself.
A supplier range the pack does not know, or a naming scheme of your own? Add your own Custom Rule from the console, describing what it should recognize.
Indexing your catalog
The getting started guide covers the full setup, from signup to your first indexed catalog. The documentation details every endpoint.
Watch the breakdown happen. The table above is the engine's output, not hand-written. The same mechanism runs on the home page, with no signup — on a hardware or fashion catalog, not plumbing. What you see there is the annotation mechanism itself, the one the plomberie pack applies to your nominal diameters and pressure ratings.