Drainpipe - this diameter is necessary

The diameter of the drainpipe depends, in part, on the ability to make a sufficient grade and, on the other hand, on the amount of filling that results. The slower the drainage, the larger the diameter must be.

Available dimensions of drainpipes

The common sizes of the drainpipes start at a diameter of 100 millimeters outside. This is also the dimension that should be installed at least inside the house. In the past, pipes with a diameter of 50 millimeters were partially laid. But this practice has created very big problems and new excavations.

Diameter of the drainage pipes

The diameter of the drainpipes each designates the outer diameter. Inside, of course, this is at least four millimeters lower.

  • DN 100 mm
  • DN 125 mm
  • DN 150 mm
  • DN 200 mm
  • DN 225 mm
  • DN 250 mm
  • DN 300 mm

Example Interplay of gradient and diameter

If, for example, a DN 100 drainage pipe is installed and an extreme gradient of five centimeters per meter of pipe is involved, the pipe can carry just as much sewage as a 150-millimeter drain pipe with a gradient of only half a centimeter per meter.

Although the pipe is only half stronger, it only needs one-tenth of the slope. This makes it clear how great the advantage for the homeowner can be if a larger pipe is laid.

DIN standards for gradients and pipe thickness

Which pipe thickness must be used as a drain pipe is regulated in DIN EN 12056-2. Here is also the clear table B 2, which clearly shows the permissible waste water drainage at a filling level of 70 percent.

Tips & Tricks

If in doubt, you should of course prefer to choose a slightly stronger pipe. If this is not possible, at least the gradient must be made stronger.

You should always remember what it means if you later have to rip open half the ground floor with tiles and laminate in order to get at a tube that is too small and replace it.

Video Board: Part 1: Plumbing code - waste and venting pipe size