In the building drainage system, PVC drainage pipes are the "blood vessels" that carry wastewater discharge, but when many people get the drawings, they are confused when they look at the signs such as "DN50" and "De110" - what exactly do these alphanumeric combinations stand for? Choosing the wrong model will not only lead to installation jams, but also may leave drainage hazards. Today, we will dismantle the model code of PVC drainage pipes, focusing on the meaning of the two core logos of DN and De, and their corresponding relationship with specifications. First, clarify two basic concepts: DN, the full name of "nominal diameter", is the "nominal size" agreed by the engineering field to simplify design, construction and procurement. It is neither the actual inner diameter nor the outer diameter of the pipe, but a "code that everyone agrees on". For example, the label "DN50" on the drawing does not mean that the inner diameter of the pipe is exactly 50mm, but that the pipe of this specification corresponds to the specific installation size and accessory system, which is convenient for people in different links to communicate quickly. Then there is De, which stands for "the outer diameter of the pipe", which is the actual outer diameter of the PVC drain pipe, and the unit is millimeters (mm). For example, "De110" means that the outer diameter of the pipe is exactly 110mm, which is the "hard index" during production - the manufacturer must produce according to this size to ensure that the accessories can be connected smoothly. Next is the correspondence between DN and De that everyone cares about the most. According to national standards (GB/T 5836.1-2006), PVC-U drain pipe commonly used specifications, DN and De have clear corresponding rules: - DN50 De63mm (nominal diameter 50 corresponds to outer diameter 63) - DN75 De75mm (nominal diameter 75 corresponds to outer diameter 75) - DN100 De110mm (nominal diameter 100 corresponds to outer diameter 110) - DN150 De160mm (nominal diameter 150 corresponds to outer diameter 160) - DN200 De200mm (nominal diameter 200 corresponds to outer diameter 200) Why is there such a correspondence? In fact, it is to balance the needs of "nominal simplification" and "actual manufacturing": DN allows designers to draw directly with the "code name" that everyone knows without remembering the complicated actual size; De allows the production and installation process to have a clear "practical standard" - for example, when buying a De110 pipe, it must be equipped with a De110 elbow and tee, so that it can fit tightly. After understanding this, if you choose a PVC drain pipe, you will not step on the pit? Don't worry, there are a few key precautions to keep in mind: 1. Don't take DN as the actual size: for example, for a DN100 pipe, the actual outer diameter is De110. If you buy a "100mm outer diameter" pipe according to the DN number, it will definitely not fit. 2. Accessories should follow De: No matter whether the drawing is marked with DN or De, when buying accessories, you must look at the actual outer diameter (De) of the pipe - for example, the De110 pipe must be equipped with De110 accessories, even if the drawing is written with DN100. 3. Look for the national standard specifications: The De size of the regular PVC drain pipe must meet the national standard. When buying, you can check: De63, De75, and De110 are all clearly stipulated in the national standard. If you encounter non-standard ones like "De105", don't buy them, otherwise the accessories will not match. 4. Look at the use and choose the specifications: for example, DN100 (De110) is commonly used for the drain pipe in the bathroom, DN75 (De75) may be used in the kitchen, and DN50 (De63) is used for the balcony floor drain. These are all calculated according to the drainage flow. Don't choose small specifications to save money, otherwise it will be easy to block. In fact, in the final analysis, the relationship between DN and De is the correspondence between the "nominal code" and the "actual size" - DN is "face", which is used for communication; De is "lining", which is used for landing. Understanding these two signs and then looking at the model of the PVC drain pipe is as simple as reading "Pinyin": for example, when you see "DN100", you immediately think "Oh, this is a pipe with an outer diameter of 110mm"; when you see "De75", you know that the corresponding nominal diameter is DN75. To summarize: In the model of PVC drain pipe, DN is the nominal diameter (nominal size), De is the outer diameter (actual size), and the corresponding relationship between the two should be based on the national standard. After understanding these, whether it is looking at the drawings, buying materials or installing pipes, you can know in your heart, and avoid making low-level mistakes because you "don't understand the logo". After all, the drainage system is a hidden project. One step wrong may require knocking on the wall for rework. To understand the meaning of the model in advance is to buy a "invisible insurance" for the house.