Choosing the size of plumbing fitting and dimensions of black and galvanized steel pipes from 1/2 inch to 1 inch - Blog déco - MC Fact

Matching plumbing fittings in black and galvanized industrial steel from 1/2 inch to 1 inch

Correspondence table between plumbing fitting size and steel pipe dimensions in mm

ThumbMetric name
(∅ inside x ∅ outside)
Designation DN
(nominal diameter)
Outside diameter (mm)Wall thickness (mm)
1/4″8/13DN813.5mm2.3mm
3/8″12/17DN1017.2mm2.3mm
1/2″15/21DN1521.3mm2.6mm
3/4″20/27DN2026.9mm2.6mm
1″ or 4/4″26/34DN2533.7mm3.2mm
1 1/4″ or 5/4″33/42DN3242.4mm3.2mm
1 1/2″ or 6/4″40/49DN4048.3mm3.2mm

Table of dimensions for inserting the plumbing screw thread into a female fitting

ThumbLength of BSPT tapered threadThread insertion (screw fitting)  Reference value
1/2″15mm to 20mm9mm to 12mm10mm
3/4″16mm to 22mm9mm to 12mm10mm
1″19mm to 25mm10mm to 12mm11mm

Calculate the size of a black or galvanized steel tube

To find out the length of tube you need, add the reference value from the table above 10mm per thread for 1/2″ and 3/4″ tubes, depending on the size of the plumbing connection, as these will be inserted into the female fitting, and 11mm for 1″ tubes.

Example of an industrial pendant lamp

If a distance of 300mm is required between the center tube and the center of the E27 socket :

Example of custom black steel pipes and dimensions of black and galvanized steel pipes for decorative plumbing fittings - MC Fact
  1. We need to know the distance between the center of the 90° elbow and the edge of the 90° elbow.
    In this case, we've opted for a plumbing connection size of 1/2″ on the 90° elbow product sheet, where you can find a diagram of its dimensions, which informs us of a distance of 28mm.
    For the equal tee fitting, the distance is also 28mm.

  2. Subtract 2x 28mm (1x for the elbow and 1x for the tee) from our starting dimension (300mm) - which gives us 244mm.
    This gives us the dimension between the 2 female elbow and tee connections.

  3. Next we need to add the part that will be screwed into the female fittings on each side.
    To do this, we take the value from the thread insertion table above.
    In our case, it's a 1/2″ plumbing fitting, so the reference value is 10mm, which we add for each female fitting (1x elbow and 1x tee).
    We'll therefore need a 264mm pipe (10mm + 244mm + 10mm).

  4. If, as in this example, the dimensions of the final steel pipe do not need to be precise, we can opt for a standard 250mm steel pipe, rather than a 264mm made-to-measure pipe.
    This will save you additional manufacturing time and, at the same time, enable you to benefit from more attractive prices.