Drawing reading and production is an explicit competence goal and the prerequisite for all design. We cover schematic diagrams, pipe routing plan and isometry, DN designation (DS/EN ISO 6708), standardised plumbing symbols (DS/EN ISO 4067) and introductory ICT/BIM and CCS coding.
Introduction
All the other articles are about CALCULATING a system — but before you can calculate, you must be able to READ the system on a drawing, and afterwards document what you have built. The drawing is the trade's common language between designer, installer and building authority, and it exists in several forms, each showing something different.
Drawing types — each shows its own
- 01Schematic diagram (circuit diagram): a schematic representation of the system's function — boiler, pump, heat exchanger, valves, tank and their interconnection. It is NOT to scale and does not show where things physically sit; it shows how the system works. Troubleshooting and understanding begin here.
- 02Pipe routing plan/floor plan: the pipes drawn into the building's floor plan, dimensioned and positioned so you can see where they run in relation to walls, rooms and other installations.
- 03Isometry (isometric drawing): a spatial, oblique projection representation showing pipe routing in all three directions at once — horizontally forward/backward and vertically up/down — without anything hidden behind anything else.
- 04Sections and details: cross-sections and close-ups of e.g. a distribution well, a heat exchanger or a wet room connection.
Isometry — that's why it's so useful
The isometry is typically drawn with axes at 30° so the three spatial directions become equally clear. It is not to scale in the same way as a plan, but proportions are maintained and each pipe section, bend and branch can be read unambiguously. Precisely for this reason the isometry is used for riser diagrams (where does the riser go up through the floors?) and for material counting — you can count fittings and measure pipe lengths directly from the drawing. For an installer the ability to read and sketch an isometry is a core skill.
DN — the nominal dimension
Components and pipes are specified with a DN designation (Diameter Nominal), defined in DS/EN ISO 6708. DN is a dimensionless, round size that roughly corresponds to the internal diameter in millimetres — but it is precisely only a designation, not a precise measurement. DN 15 is not necessarily 15 mm internally, and different materials with the same DN can have different actual dimensions (see "Pipe content — how much water is there in the system"). DN is used to order and match components, valves and fittings so they fit together — not to calculate cross-section.
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