Two documents, two jobs
A catalogue is a price list with pictures. It is built to help somebody choose, and it does that job well: the shapes, the families, the finishes, the mount types. What it cannot do is tell you whether the pan will fit the room you are standing in.
A technical drawing is a different instrument. It describes the geometry of the fixture — where the waste goes, how deep the body is, how high it stands, where the fixings land. Those are the numbers that decide whether a specification becomes an installation or a variation order.
Buyers get into trouble by using one document for the other’s job. They select from a catalogue, quote from a catalogue, and discover the problem when the trap does not line up with the pipe. The fix is not to distrust the catalogue. It is to know which questions each document answers, and to insist on both before a price becomes an order.
What the catalogue is for
A catalogue is a selection tool, and used as one it is efficient. It answers: what families exist, what each family looks like, which mount types are available, which finishes a model is produced in, and how the range sits together.
That last point is undervalued. A catalogue tells you whether a family is coherent — whether a two-piece WC, a wall-hung pan and a bidet share a design language, or whether they were collected from different sources and photographed together. For a wholesaler building a shelf, or a hotel choosing a bathroom, coherence is a real specification item that only a range document can show.
What a catalogue cannot tell you is anything that depends on the building. It does not know your wall, your floor, your drainage or your supply. It also cannot tell you whether the model in the photograph is the model in the price list, because the photograph was taken of a sample and the price list is a list of codes.
What the drawing set is for
A drawing set is an installation document. It exists so that a plumber, a contractor or a project engineer can position the fixture and connect it without guessing.
Six things should be legible in it. The plan view, showing where the waste centre falls relative to the finished wall. The section, showing the trap and how it sits inside the body. The elevation, showing the height of the rim and the overall envelope. The fixing positions, including the centres for floor bolts or the frame for a wall-hung pan. The supply and inlet positions, with the connections identified. And the wall or floor cutout where one is required, drawn to the same scale as the rest.
A set that has five of those and not the sixth is not a drawing set; it is a marketing sheet with a scale bar. The missing one is usually the fixing detail, which is also the one that generates a site question on the morning of installation.
The four dimensions that decide whether it fits
Four measurements carry most of the risk in a sanitaryware installation. Our own dimensional data for specific models is not published in this article, so the description below is about what each measurement decides rather than what any particular value is.
Rough-in. The distance from the finished wall to the centre of the waste. It is the first thing to check and the last thing to change, because it is set by the building’s drainage. If the pan’s rough-in does not match the pipe, the options are an offset connector, a change to the drainage, or a different model — and only the first is cheap.
Overall depth. The distance from the finished wall to the front of the pan. It decides circulation in a small bathroom, whether a door can open, and whether a person can stand at a basin. Two pans with the same rough-in can differ here, which is why rough-in alone is not enough.
Height. The rim height and the seat height, measured from the finished floor. This is where accessibility requirements, counter heights and the operator’s standard land. It also interacts with the wall-hung frame setting, so it is agreed between the fixture and the structure rather than chosen from a list.
Fixing centres. Where the bolts or the frame anchors land. For a floor-standing pan this decides whether the existing holes can be reused; for a wall-hung pan it decides whether the in-wall frame is compatible. A change here is a building modification, not a plumbing adjustment.
Three consequences of quoting from a catalogue alone
The failure is rarely dramatic. It is administrative, and it compounds.
A quotation that cannot be built. The price is correct for the model and wrong for the project. It then has to be reissued against a different model, which restarts the approval, the sample and sometimes the currency. The cost of that is measured in weeks.
A substitution that fails at the wall. A model is swapped for an equivalent from the catalogue, the equivalent has a different rough-in or a deeper body, and the problem surfaces during installation. On a single bathroom this is an inconvenience. On a hundred rooms it is a variation with a programme attached.
A comparison that is not a comparison. Two quotes for two models, compared on price, when the models differ in depth or in fixing arrangement. The cheaper one may need a different frame or an offset connector, and that cost never appears in the comparison because it appears later, in a different document.
How to read a drawing set quickly
Most of what matters can be found in a few minutes if you read in the right order.
- Title block and revision. Which model, which revision, which date. A drawing without a revision is a drawing you cannot cite.
- Scale and units. Confirm both before reading any figure. A drawing read at the wrong scale produces confident nonsense.
- Plan view for rough-in. Check where the waste centre sits relative to the finished wall, not the structural wall.
- Section for the trap. Confirm the trap type and whether an alternative arrangement is offered.
- Elevation for heights. Rim, seat and overall envelope, all measured from the finished floor level.
- Details for fixings. Bolt centres, frame type, and any cutout that the building has to provide.
If a drawing set does not contain those six, ask for the missing sheet rather than inferring the number from a photograph. A factory that has a proper set can send it; one that cannot has told you something about how it will answer a technical question later.
What to send so the answer is about your building
The quality of the reply depends on the quality of the question. Four things turn a general enquiry into a specific answer.
The building’s drawing, marked up with the finished wall and the finished floor level. The wall build-up, because a wall-hung installation depends on what is inside the wall as much as on the face of it. The drainage arrangement, including the trap type already present or planned. And the destination market, because the certificate set and the model availability depend on where the goods are going.
Send those and the reply stops being a catalogue page and becomes a set of documents about your project: the drawing for the models that fit, the certificates that cover them, and a note on anything that needs to be resolved before the order.
That is a slower first exchange and a much faster project. The catalogue will still be useful, but it will be doing the job it was built for.
Frequently asked questions
Can I specify a toilet from a catalogue alone?
You can choose one, but you cannot confirm it fits. Selection needs a catalogue; installation needs a drawing showing rough-in, depth, height and fixings. Quoting from a catalogue alone produces a price that is right for the model and may be wrong for the building.
Which dimension matters most?
Rough-in, because it is set by the building’s drainage and is the hardest to change afterwards. Depth and height affect comfort and circulation; fixing centres affect whether the existing floor or frame can be reused. Rough-in is the one that decides whether the model is possible at all.
Do your drawings show dimensions for every model?
The drawing set is issued per model and covers rough-in, overall dimensions, fixing positions and connection points. Rather than quote figures here, where they would be detached from the drawing that gives them meaning, send the model you are considering and the set will be sent against it.
What if the rough-in does not match my drainage?
There are three routes: an offset connector, a change to the drainage, or a different model with a matching rough-in. The first is usually the least disruptive and the last is usually the most reliable. Which one applies depends on the actual distance and on what the floor construction allows.
Is a wall-hung pan harder to specify?
It needs one more document: the frame and the wall build-up. The pan’s own drawing will not tell you whether the wall can carry it or where the frame sits. That is why a wall-hung enquiry should include the wall construction, not only the fixture schedule.
How do I check a quotation against a drawing?
Put the model code from the quotation next to the drawing’s title block, then check the four measurements against the building. If a figure on the quotation has no drawing behind it, ask which sheet it came from. A quotation that cannot be traced to a drawing is a price, not a specification.
Related on this site
Documents and certificates
- Catalogues, the technical drawing set and the published test reports
- Send a drawing and ask which model fits it
Related reading
- Reading a sanitaryware spec sheet
- Toilet dimensions: what each number decides
- Showroom or Catalogue: What Wholesalers Ask